Your stupidest mistakes - Page 1
Forum section: electronics / projects

author: obrien
author_rank: Contributor
timestamp: January 10, 2017, 03:54:57 pm
content: Hi,Can you please take a while and laugh at my stupidity? ThanksOf course I realized it, when it was already being make.Feel free to submit your mistakes so I do not feel alone

author: obrien
author_rank: Contributor
timestamp: January 10, 2017, 04:00:18 pm
content: BTW I did a search to find a similar topic but I could not find it. But I am new here, it if exists please point me there

author: filssavi
author_rank: Frequent Contributor
timestamp: January 10, 2017, 04:09:17 pm
content: I don't know if it's my stupidest but it's pretty up there...A couple of years ago I was working to diagnose a glitch in the electrical system of a formula SAE car that randomly turned off the car that turned out it was a faulty relay connector (the relay itself was fine), since it was late at night after a day of work/study I was quite tired and didn't realize that I had connected the car backwards, goes without saying that a control unit I made the previous year (actually the first board I designed) didn't have reverse polarity protectionfortunately I had a Ti DC/DC step down (don't remember exactly which one) that I wasn't using that year, that sacrified itself (the soic-8 package had nicely exploded) failing short circuit and protecting the usefull things on that rail

author: Asim
author_rank: Regular Contributor
timestamp: January 10, 2017, 04:11:29 pm
content: Ouch, my stupidest mistake would be connecting 7805 regultor & lm317 to the same heat sink with no insulation.So basically shorting the tabs together ( lm317 tab is vout while 7805 tab is ground )

author: dekra54
author_rank: Unknown
timestamp: January 10, 2017, 05:09:56 pm
content: My stupidest mistake was to mix up 2 Strings from a PV system in a connection box on the roof. It was all fine when i connected the first inverter in the basement. But when i got to the second connected and starting things started to go wrong. The 2. inverter showed an overvoltage warning but unfortunately the voltage was so high due to my wiring mistake that in the few second it took me to shut down the inverter a few hundreds of milifarad 500V caps inside the inverter started to explode. I measured it after i got it all sorted out and the inverter was getting 1650V DC because the first inverter was connecting 2 strings in series

author: gnavigator1007
author_rank: Unknown
timestamp: January 10, 2017, 05:26:44 pm
content: All of my stupidest mistakes involve late nights, too much caffeine, and forgetting to unplug something before digging around. Makes all of my other mistakes seem quite reasonable.

author: Howardlong
author_rank: Super Contributor
timestamp: January 10, 2017, 05:52:02 pm
content: Joining EEVBlog and finding I now had 20 oscilloscopes when I'd lived perfectly happily with one or two for a couple of decades.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: January 10, 2017, 09:26:19 pm
content: Quote from: gnavigator1007 on January 10, 2017, 05:26:44 pmCan agree a lot, every-time something that should work, doesn't work, and its late night I, try to debug it for a few hours then just say to myself "I will fix it in 5 minutes when I will wake up" and in 100% of the cases I was right.

author: kcbanner
author_rank: Contributor
timestamp: January 10, 2017, 09:30:04 pm
content: Always review your board design the next morning instead of ordering them at 2am.

author: GreyWoolfe
author_rank: Unknown
timestamp: January 10, 2017, 09:39:12 pm
content: About 4 years ago someone gave me a couple of old Tek scopes. I plugged them in and turned them on without the benefit of a variac or dim bulb tester ( I have both now). The first scope, which didn't have a cover on it, powered up fine and I saw traces. Plugged the second one in and nothing happened. I saw the modules in both scopes were the same so I thought that I would test the modules from the second scope in the first scope. The first module worked. After powering the scope with the second module, I heard a loud pop and a tongue of flame came out of the scope. Naturally, the smell lingered in the house for a couple of days and SWMBO was not a happy camper. She made me put the scopes out on the curb with a stern warning not to bring them back in. As she has half the money and all the vagina, I listened.

author: slurry
author_rank: Regular Contributor
timestamp: January 10, 2017, 10:01:00 pm
content: Spent three hours fault finding on a headphone amplifier i built, the audio on one channel was extremely weak.I traced the audio all the way to the last output transistor pair where the audio went missing,finally i replace the transistors with no luckI was tearing my hair until.... i realized i had connected the headphone jack with the missing channel to ground pin and the ground pin to the missing channel

author: Benta
author_rank: Super Contributor
timestamp: January 10, 2017, 10:06:44 pm
content: My worst mistake ever...throwing away all my old databooks (Motorola, Texas, National, Linear, Harris, you name it), because with CDs and the Interwebs they'll no longer be needed.Boy, was I mistaken. I'm still crying.

author: David Hess
author_rank: Super Contributor
timestamp: January 10, 2017, 10:17:23 pm
content: I once swapped the vias where the output capacitor was routing power and ground from one side of a board to the other so power and ground were reversed on one side. At least since the mistake was in one spot, just cutting the traces and adding a pair of jumpers was enough to fix it.

author: Vgkid
author_rank: Super Contributor
timestamp: January 10, 2017, 10:39:40 pm
content: The one I laugh about:Diagnosing why my cars battery kept dying. Put the battery on the charger overnight. Had the battery tested, it was good. Put the meter in series with the battery and the (+) connector. I blew that fuse. CRAP, grabbed the meter, made up a quick test to see if the 10A fuse was good, it was. Went back at it, the car drew a few amps. The diode bridge had a few open diodes(I wish they actually stocked those). With the meter still bolted to the terminal set the meter down on the battery. A few seconds later POP. The other probe managed to hit the opposing terminal,instantly destroyed. Still haven't replaced the fuses.The one I cry about:I got a broken genrad 1689, had to sneak it out in a duffel bag* interesting story about that.Got it home, gave me every error message except bad memory. It was really late, pop the covers off, thinking what is the worst that can happen. Start checking voltages, they are good. Unplug the power connector. They were smart with, you can flip the connector around and it will still work. Plugged it in,put the covers loosly on(I was going to resume in the morning). Next morningPlug in the power cord, press the power button. Lights flash, fan runs, then the display goes black. Take the covers off, realize that when i plugged in the ribbon cable from the psu. I had shifted it by one pin. One rail was left floating, one connected to ground, the +/- rails were inverted.Sigh...

author: dexters_lab
author_rank: Unknown
timestamp: January 10, 2017, 11:08:04 pm
content: like me putting in a PAL20V8 IC backwards? that was pretty stupid

author: Highvoltagefox
author_rank: Newbie
timestamp: January 11, 2017, 12:28:27 am
content: Replaced the cord on a clothes dryer and didn't know my fingers were touching the contacts when plugging in. Woke up on the other side of the room. Good times..

author: rs20
author_rank: Super Contributor
timestamp: January 11, 2017, 12:51:34 am
content: Probably stupidest mistake was touching my oscilloscope ground to the wrong tab on the output of my LED strip controller; which created some complex fault loop including my PC's 5V USB supply, isolated supply's 24V output, and oscilloscope earth. Had to replace most of the ICs on the board, but at least I did manage to fix it. The thing that makes it worse is that I actually only wanted to measure DC voltage, but couldn't find the multimeter or leads; so if I had been careful enough with the oscilloscope ground, OR organized enough to have the multimeter to hand, nothing bad would have happened.In a similar kind of story, I was once heating some copper hydroxide in a beaker to convert it to copper oxide to make it better for disposal. I wanted to loosely cover the top to keep the heat in, without creating a seal. But I couldn't find my watch glass (a small piece of concave glass that is designed for exactly this purpose), so I stupidly thought it'd be alright to just loosely place a normal rubber stopper on the beaker, without pushing it down. A few minutes later, I hear a slight "whistling" sound, see some gas working its way past the rubber stopper in one particular place. To my brain's credit, I realised I should sprint out of the room immediately. The stopper had somehow worked its way down to form a seal under gravity, but now the seal was failing. About a second later, the stopper pops off, and the pressure drop causes a huge boilover, with scalding copper hydroxide spraying in every direction, including on the wall exactly behind where I was standing a few second earlier. Luckily I was out of the room by then. As if that wasn't stupid enough, I later discovered that the watch glass (that I couldn't find) was in front of me the whole time.And for my "tip of the day": I designed a PCB late last year, but held off submitting it because PCB shop was closed for holidays. So I decided to go ahead and write the firmware for the MCU on board, and in the process of working through that, discovered a couple of mistakes in the PCB (e.g. LEDs connected from open-drain pins down to ground.) I might make a point of doing firmware in advance more often in future, as it's much easier to fix these issues in the digital world!

author: M4trix
author_rank: Frequent Contributor
timestamp: January 11, 2017, 01:25:44 am
content: Quote from: Howardlong on January 10, 2017, 05:52:02 pmI'm still resisting ! I have one analog oscilloscope and since I'm only fiddling with audio amplifiers, I need it for observing sine wavesand the clipping level. Digital ones still can't beat the analog in this field.

author: retrolefty
author_rank: Super Contributor
timestamp: January 11, 2017, 01:28:21 am
content: In the early 80s, while I had read that all unused input pins on a simple CMOS logic chip should be pulled up or down I failed to do it and touched the chip on a solderless breadboard. Damn blister took months to heal, but lesson stuck.

author: retrolefty
author_rank: Super Contributor
timestamp: January 11, 2017, 01:30:48 am
content: Quote from: M4trix on January 11, 2017, 01:25:44 amMany here will disagree with you, but I too have been happy and well served with my vintage Tek 2213.

author: Alex Eisenhut
author_rank: Super Contributor
timestamp: January 11, 2017, 01:31:24 am
content: Have made many. My first tech job I was using OrCad SDT, this was 20 years ago. I made my first schematic and PCB, and when I powered up the board it worked. As I was working on it I noticed the current consumption crawl up slowly (nice old meter movement). I was too excited to work on my first board to really pay attention to the simple power supply.Eventually the current consumption went way up and the tantalum caps on the board caught fire.Turns out the polarized capacitor symbol had swapped pin numbers compared to the footprint. I didn't check any of that, I assumed it was all good.Since then I always check every symbol and footprint.Other mistakes include taking the DC rating of a scope probe and not checking frequency derating. I was working on a high voltage (KV) AC power supply, I just grabbed the "HV" scope probe and slapped it on the test point and smoke started coming out the other end of the probe cable... that's where the compensation network lived...

author: Mr.B
author_rank: Unknown
timestamp: January 11, 2017, 01:53:41 am
content: My biggest goof in the last couple of years...One off project for a family friend.16 x 16 LED matrix, all SMD, controlled by shift registers. My friend was going to do the MCU side himself.16 n Fets on the columns, 16 p Fets on the rows.I got the p Fets upside down in my schematic.All the rows were always on because of the body diode.Unsoldered all p Fets.Re-soldered all at a strange angle.Added 16 little bodge wires.When my friend saw it, he asked "whats going on here?".My reply - "Bad day syndrome. It happens."Lesson learned: Triple check your schematic and board layout before sending the gerbers to China.

author: eugenenine
author_rank: Frequent Contributor
timestamp: January 11, 2017, 02:02:28 am
content: Quote from: obrien on January 10, 2017, 03:54:57 pmIt depends on if your doing conventional current flow or electron flowThe old PIC microcontrollers that were UV erasable, if you connect them backwards they emit lightThinned down my collection of books too much. Gave away a bunch of parts I wish I'd kept. Got rid of a bunch of computer stuff I wish I still had.

author: David Hess
author_rank: Super Contributor
timestamp: January 11, 2017, 03:03:28 am
content: Quote from: retrolefty on January 11, 2017, 01:30:48 amYou guys are so far behind the times; move into the digital age; my go to oscilloscope is a 2232. You should always have at least two oscilloscopes so you can use one to repair the other; two of several different oscilloscopes is even better.Mistakes to go along with swapping power and ground on half of a printed circuit board layout that I mentioned earlier:1. Designed and built a 1000 volt DC stroboscope power supply with way too much output capacitance and no safety enclosure. Shorted it between my index finger and elbow but at least my whole arm only hurt about a week after getting thrown off of the ladder, across the garage, and onto the concrete.2. Picked up a powered 25kV neon sign transformer by the insulators, but at least I set it down instead of dropping or throwing it. A neon indicator wired to the primary would have been handy.3. Managed to create a ground loop through the first DSO I used with those neat and tiny micrograbber ground clips; at least the ground clip only turned white hot and melted.4. Was not paying enough attention and fumbled a glass bottle of concentrated nitric acid trying to set it back on the shelf while wearing shorts in the chemistry lab pouring it all down my leg. The skin on my leg turned grey instead of the usual yellow from nitric acid before pealing off and the hair only took a couple years to grow back.

author: JacquesBBB
author_rank: Frequent Contributor
timestamp: January 11, 2017, 03:15:06 am
content: Maybe this thread would be better placed in the General Chat section.

author: mmagin
author_rank: Frequent Contributor
timestamp: January 11, 2017, 03:47:23 am
content: The most embarrassing one I can think of is this rather bulky portable Agilent base station test set (i.e. a spectrum analyzer somewhat specialized for stuff related to mobile phone network stuff).Now, I got it cheaply in non-functional condition. But in trying to disassemble it incorrectly I managed to break the PC board that acts as a feedline from the input connectorI still have to try fixing that up again. May just try replacing the broken part with a length of .141" semi-rigid coax and a matching panel bulkhead mount connector and carefully tack the other end to the broken board. I think the actual problem might be a power supply issue, same as a similar model Shahriar (The Signal Path) fixed in a video on his channel. (Edit: this is the one, wish I'd watched it before making that mistake!)

author: BradC
author_rank: Super Contributor
timestamp: January 11, 2017, 03:49:52 am
content: Had a jury rigged protocol analyser comprised of a PIC on breadboard connected by USB to a laptop (an extremely expensive laptop) connected up to a mains power meter while reverse engineering the comms protocol. No problem as everything was floating with the laptop on battery. Noticed laptop battery getting low, so plugged the adaptor in. Laptop no longer floating with the associated smoke and flames.First kid was only a matter of a few weeks old. I blame sleep deprevation. Frustrating thing was the isolation transformer was in the next room, I was just too lazy to use it.

author: mmagin
author_rank: Frequent Contributor
timestamp: January 11, 2017, 03:57:44 am
content: Quote from: David Hess on January 11, 2017, 03:03:28 amThis reminds me of how I ended up owning four scopes, two of them 500 MHz scopes. First I got a HP 5370 counter. Then I realized it's clearly a bit out of calibration, so I start looking at the service procedures. Most things I have covered, but I don't have a really fast pulse generator (they specify the HP 8082A) nor do I have anything faster than a 100 MHz scope (they specify one of those HP portables that was hot shit in the late-70s.) So now I have an HP 8082A. I also have a Tek 7904 (I already had a 7613, so another 7000 series scope seemed like a great idea.) But getting the 7904 properly working has been an adventure, so I've gotten a HP 54615B which was cheap and entirely working. (But I can't sell my 54645A -- it's a lot lower bandwidth, but it has a lot less memory depth.) At least I gave away the Tek 468 that was truely redundant for me.(I'm not counting a Tek 323, it's so tiny and lives elsewhere.)

author: Powermax
author_rank: Regular Contributor
timestamp: January 11, 2017, 04:41:23 am
content: When constructing my first computer build, (the computer I am currently on) I was debugging a legacy PCI card and when I plugged it back in something shorted and caused the computer to shut down. (did not know PCI was not hot-pluggable at the time, I learned that the hard way!)I could not get the computer to boot after that for some reason. Resetting the CMOS worked, but all of my PCI slots died!Legacy PCI, PCIe 4x, PCI8x, PCI16xv2 (for the graphics card I was going to install in the future) Only 2 small PCIe 1x slots survived.Since I was having problems with those to begin with, I tried to ship it back as DOA ( PCI were troublesome and something else) but the board came back claiming that the CPU pins were bent. Sure enough, when I looked, it appears as though someone stuck their thumb all over the socket, bending over half the pins! I know that wasn't me, it had to have been ASrock.So I spent half an hour tediously bending all the pins to as close to where they belonged as possible. I broke one pin but the board does work except for the most of the PCI's.I still suspect it's a very simple issue, I think I vaporized a power or ground trace somewhere, but I do not know the pinout of PCI slots to verify. Given that it was a legacy PCI, which is not natively supported on Z77 chipset, there is a logic chip responsible for essentially converting PCIe into legacy PCI, and I suspect this chip may be blown. It's a really small package so I don't think I'm going to risk trying to replace it without proper equipment.

author: Powermax
author_rank: Regular Contributor
timestamp: January 11, 2017, 05:32:00 am
content: I have a load of stories I can tell about my quadcopter project(s) as well!I managed to kill not 1... but2!! microcontroller boards, due to the same mistake that occurred in different ways. The microcontroller board in question is essentially a modified arduino a few sensors on it. Called the Multiwii board.I had a ratsnest of wires of the quadcopter wired up on my bed and was working on fixing the frame after a crash. The Multiwii board was mounted directly on top of the power distribution board, which connects to a 3S LiPo battery capable of delivering over 1KW. While it was apart, some guests arrived and I left the board alone next to the distribution board while still connected. When I came back and hopped back on the bed it moved just enough to short out and many wires went up in smoke, along with the multiwii.Then I had another incident where my OSD display was not functioning properly. Strangely it worked whenever I got my scope out and hooked up the ground. As soon as I disconnected the video out from it back to the transmitter I did not have an OSD overlay from the camera video, or that the picture was really fuzzy, I don't remember anymore. I realized an hour later that while video was being connected, the ground was not connected on the OSD board!Well I connected it up to 12V as the board requires 12V to go into a small 5V switching regulator, but I had the plug one pin over too far, so the grunty 12V from the distribution board shorted to the ground on the board. It blew the board, as well as the main multiwii board.After receiving the replacement boards, I rewired the whole thing so that the minumOSD board no longer required 12V.more recently, I was rewiring the quadcopter and my hands slipped and well same as before 12V got connected to ground, causing a whole bunch of wires to go up in smoke. At this point I was so frustrated with my clumsiness and having to keep buying replacement parts. I mean, I literally just fried the minimOSD board, the multiwii flight controller, a I2C to UART converter board, and a GPS module, literally everything!!!Once I recovered from my mental breakdown, I decided to make my own flight controller board with a old dusty arduino I had lying around. To my amazement, although I killed the ATmega328 chip on the board, a small low dropout regulator (which sacrificed itself) protected all the sensors. I have a box of shame which all dead electronics go to in case I need them later for some reason. Furthermore I discovered that the GPS module that smoked when I tested it by wiring it to a USB FTDI adaptor only smoked because a reverse polarity protection diode which blew and shorted. After desoldering and replacing it, the thing worked fine! And because my arduino mega has more available UARTs, there was no longer a need for a separate board to allow the UART GPS to interface to the multiwii! And not only that, but the mega, due to it's increase processing power, allowed me to enable more features in the later releases of the multiwii code, such as navigation!!! So it turned out to be a win-win!So after all that, my quadcopter is now a simple DJI flamewheel frame with a arduino-mega double-sided sticky-taped to it, with a rat's nests of wires going every which way, as well as a plastic cutout mounted on top of it with holes for the standoffs for the old multiwii board, some wires connect the I2C bus on that board directly to the arduino mega which allows sensor data to be collected by the mega. Directly on top of it I have the GPS module mounted with more wires going to the mega, and I had then cut out a small perfboard and mounted four servo headers for the 4 ESC's (brushless motor controllers). It's a ridiculous mess but it WORKS!!! (well, most of the time, anyway.)

author: kaz911
author_rank: Super Contributor
timestamp: January 11, 2017, 08:04:46 am
content: My first (as far as I remember) and stupid'est mistake - was when I was 7-8 years old. I wanted to make the door to my room automatic. So I rigged a small motor and a counter weight up. The motor was 220v and plugged into a socket next to the door with the old euro "exposed" 2 pin plugs 220v. I used wire for the motor and counterweight - and while "securing" the counterweight with the metal wire by twisting it around - the other end of the stiff'ish metal wire landed on the 220v plug and of course shorted on the two pins.I got a huge boost of 220v through me - but fortunately the wire burned over and then popped the breaker. It took a day or two before I finished the project and my parents never found out - apart from they thought it was strange their clock-radio in their bedroom showed the wrong time......I could have won a Darwin Award for that.... But I got my automatic door

author: Scrts
author_rank: Frequent Contributor
timestamp: January 11, 2017, 07:29:19 pm
content: In early days, I've tried to check the resistance of the 220v in the socket... The smoke from the analog multimeter burnt my eyebrows

author: ZeTeX
author_rank: Frequent Contributor
timestamp: January 11, 2017, 07:51:46 pm
content: Quote from: Scrts on January 11, 2017, 07:29:19 pmdefinitely not a fluke multimeter

author: Inflex
author_rank: Regular Contributor
timestamp: January 11, 2017, 09:37:23 pm
content: Working in Africa, late at night, trying to woo a lady, replacing EU 220V plugs on IEC leads with the South African monster plug, grabbed the wrong end of a lead, which happened to be plugged in to the wall, the blade vaporised leaving a 1/4" hole in it, leaving me blinded, shocked and racing down the hall way to check that the AS/400 mainframe was still running, as the lead was plugged in to the UPS outlets.... did I mention I was trying to woo a lady?

author: Pinkus
author_rank: Frequent Contributor
timestamp: January 11, 2017, 10:17:51 pm
content: Quote from: Benta on January 10, 2017, 10:06:44 pmOuch - this remembers me that I sold all my vinyl records for small money because CDs were so much sophisticated.....But back to the topic: the worst thing I can think of was producing 500 PCBs for a customer where the planned D2PAK voltage regulator was not available on stock. So I purchased a similar replacement regulator .... not recognizing that the main tab was not GND but Vin at this regulator. I did not found out before the 500 units were produced and shipped to me and were not working. I can tell you: manual desoldering of 500 D2PAKs is a nightmare. Lesson learned.....

author: Inflex
author_rank: Regular Contributor
timestamp: January 11, 2017, 10:20:56 pm
content: Quote from: Pinkus on January 11, 2017, 10:17:51 pmBeen there, experienced thatAt least it was only 100 in my case.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: January 11, 2017, 10:40:19 pm
content: Biggest stupid mistake was "Don't take it apart, turn it on!". This resulted in clouds of black smoke pouring out of the back of an old Heathkit scope that had been rewired for 110v as the previous owner could only get a 240/110v site transformer for isolation. Took a week to get rid of the smell. Scope was not recoverable.

author: eblc1388
author_rank: Frequent Contributor
timestamp: January 12, 2017, 12:22:59 am
content: Directly powering a small electronic device which use a 9V cell from a DC supply.As I have a spare 9V battery clip at hand, I thought it would make a much better connection than using just the crocodile clips alone. I connected the red lead of the spare battery clip to positive and black lead to negative of DC supply output. Finally, the spare clip was mated with the battery clip in the device.I'm 100% sure the connection was correct, but....

author: Inflex
author_rank: Regular Contributor
timestamp: January 12, 2017, 12:25:52 am
content: Quote from: eblc1388 on January 12, 2017, 12:22:59 amWhooops, yes, that can be easy to happen with those 9V connectors.

author: nctnico
author_rank: Super Contributor
timestamp: January 12, 2017, 12:28:10 am
content: I just let the magic smoke escape from a relay. No, not from the coil!Edit: took it apart and a picture:

author: joeqsmith
author_rank: Super Contributor
timestamp: January 12, 2017, 01:08:32 am
content: Quote from: Inflex on January 11, 2017, 09:37:23 pmAnd let's here the rest of the story.My mistakes are far too many to post. Even the mistakes in my posts are too many to post.A long time ago, I was working on a project that had a microphone. I went to wire it in and there was a red, black and some other color. Being rather cocky, I assumed I knew what I was doing and did not read the data sheet. Red is not always positive and black is not always ground. This was a $70 mistake but a lesson learned. Read the data sheet....

author: Inflex
author_rank: Regular Contributor
timestamp: January 12, 2017, 03:25:25 am
content: Quote from: joeqsmith on January 12, 2017, 01:08:32 amPlease to report that was the only disaster for the night, everything else was a greater success18 years ago now, still have the pocket knife as a reminder.

author: drussell
author_rank: Super Contributor
timestamp: January 12, 2017, 04:35:07 am
content: Quote from: Powermax on January 11, 2017, 05:32:00 amYou do realize they make these things calledfuses, right?

author: Powermax
author_rank: Regular Contributor
timestamp: January 12, 2017, 05:48:20 am
content: Quote from: drussell on January 12, 2017, 04:35:07 amWhat my quadcopter really needs is a complete re-wiring, and making a PCB with all the parts on one board. Maybe a ruggeduino too.

author: peteb2
author_rank: Regular Contributor
timestamp: January 12, 2017, 06:15:33 am
content: I look down upon my 57yr old knuckles at the scars from RF burns that happened a good 30+ yrs ago. I was just out of school and i had been lucky enough to earn a position as a Tech-trainee with the nation's State Broadcast Radio...It was my 1st night at the transmitter site to be shown what transmitter maintenance was all about. I was there with my supervisor and i was to learn-by-doing how to shutdown each of the 5KW halves to what was an aging valved (tube) AM Radio Transmitter, change the output coupling over and bring up a spare while we put the main into a dummy load and run the tests.It was well past midnight. The supervisor was thinking about lots of other things and i had never in my life seen such gear. He yelled over the noise of ducted air; "Stand on that old wooden chair, up by that big frame full of heater coils (the load i was told) at the back of the cabinet and when i shut off the plate volts you'll hear the breakers bang out so spanner undo that huge brass nut on the insulator and swing the brass link onto the Load and tighten it up".Upon the sound of his voice of "GO" I did exactly as he said, (only he switched off the plate volts to a totally different cabinet and did not notice)! I heard the bang as he said would happen so i simply UNCOUPLED THE LIVE 10KW transmitter and joined it to the load. Yes i was impressed by the little bits of lightning that came off and out of my fingers as it did it and how the load turned into a white hot stack for a microsecond, dimming to a red glow and then just back to a warm heat... as my ears rang to the sounds of what had been BANG, BAAANG and BOOM...There was an alarm of some sort going off so i came down off the wooden chair emerged from the rear of the cabinet and saw my super looking confused; "WHAT, What ... what"...Then we looked at the finals through the cabinet window (airblast glass tubes) which both had holes right through their plates.... He quickly turned the entire TXr off, we opened to doors to see loads of damage... bits of exploded big ceramic capacitors and what he called the final drivers (tubes) with melted glass.That's when i mentioned my hands smelt like Kentucky Fried Chicken and were kind of sore. The super wasn't really that interested and was completely furious.We stayed there all night, we'd enough spares and had the poor TX running again on half power for another crew who specialized in such intensive repair work to take on the job of rebuilding the mess another day.My hands took weeks to come right with all the little burn blisters deep inside. I was told was how lucky i was it because it could have been way worse....!These days i guess OSH would have been over everything!

author: tautech
author_rank: Super Contributor
timestamp: January 12, 2017, 07:40:04 am
content: Great story peteb2.I'll forever be watching for a guy my own age with scarred knuckles and then I'll know it is you.Going away for a couple of weeks so thought it was best to power off the PC rather than leaving it in sleep mode....you know thinking green.Turned it off at the wall in fact, and thinking little about it as one would, flicked the switch on return only to be greeted with a loud pop.Dead as a Dodo bird she was with that unwelcome smell of fried electronics.Hell, it's not that old for a PC, what's wrong ?It was winter and some mangy little bug had crawled into the PC PSU to keep warm and unwittingly used its body to create a bridge between an HV point where a SMD resistor had lessened the gap between the PCB and the ATX metal case. Now that wasn't the problem per se, rather that I'd turned off the power that kept the mangy bug in a nice dried/fried state and without it the little bugger was free to absorb a couple of weeks of moisture to then become conductive.Now the stupid bit begins:Bugger it's my main PC and not worth shagging around with so off to the PC doctor for a new PSU....built a few, I know what I'm doing, besides I've got all this EEVblogging to catch up on.Hurry, hurry, wack the new PSU in and with X'ed fingers turned it on. No go, bugger.Oh shite, the mobo's friedso off again for another mobo from the doctor....can't get the same processor socket anymore.So hand deep in pocket fishes out for new moboandprocessor and shoots home to throw it all together.Gather tools, remove covers only to find some dumbass hadn't connected the 4 pin ATX 12V supply lead.Got a spare mobo and processor though.There's one born every minute....there's one born every minute.....there's...................................

author: Inflex
author_rank: Regular Contributor
timestamp: January 12, 2017, 07:46:34 am
content: Quote from: tautech on January 12, 2017, 07:40:04 amThat catches me out about as often as forgetting to put a stick of RAM in to the laptop mainboards after I've been doing rework on them "Cursed thing still wont POST! (wastes another hour)"

author: matseng
author_rank: Frequent Contributor
timestamp: January 12, 2017, 08:11:20 am
content: I needed one more cable connected to 5 volts while debugging an old arcade game board. So I hooked the wire up to the sense input on my PSU without checking that the "shortening bar" between the +out and +sense on the PSU was securely tightened.It wasn't. :-( The sense got some random half-floating voltage from the PCB and the PSU promptly jacked up the 5 volts in order to compensate....Two dozens of unsockeded TTLs and the CPU blew. By some reason the uv-eproms managed to stay alive.

author: tautech
author_rank: Super Contributor
timestamp: January 12, 2017, 09:04:30 am
content: Another some 35 years earlier while working in a small engine business, happened after spilling some petrol down my leg......thought little of it at the time.We wore calf high lace up steel cap work boots, mine had a fluffy band at the top that in dirty environs would prevent any loose matter from getting down your boots.Except liquids. Oh well, wet petrol foot would smell better than they usually do.Rushed off our feet we were, flat out serving customers, one having something that needed grinding....I'll do it and out the back I went and you can well guess what happened next.Hot footed it out of the workshop. which luckily had a tap just outside to douse the flames that threatened to cauterise the family jewels.I don't normally mind the smell of cooking meat but when it's your own...bugger that.I ended up with a raw ring completely around my calf that when healed looked for all the world like the original Aussie birthmark.I swear I have no Aussie breeding in my ancestry....I swear I don't.

author: LHelge
author_rank: Contributor
timestamp: January 12, 2017, 09:49:47 am
content: I also have a multicopter related incident. 5-6 years ago I was developing my own quadcopter controller. I brought it to our countryside cottage over Easter to finalize tuning of the PID controllers.To control the motors I used standard RC motor controllers. These take a PWM signal in where a 1 ms pulse means 0% throttle and 2 ms pulse means 100% throttle. If you power up these motor controllers with 100% throttle request and then change to 0% throttle you can calibrate the endpoints on the throttle curve to your timings (if you aren't spot on 1 ms and 2 ms). I created a calibration firmware which looked like this pseudocode:Code:main() {setThrottle(100%);wait(4 s);setThrottle(0%);while(1);}It worked great to perform calibration.When I was working on the PID-tuning I had some problem which I cannot remember, but I suspected it had something to do with throttle calibration. I started flashing the calibration firmware but forgot to disconnect the battery leads first. This resulted in the (very overpowered) quad running at full throttle for 4 seconds cutting up my left hand with its razor sharp carbon propellers. My SO was not happy about spending the Easter driving me the 1 hour drive to the ER and back, and waiting for them to stitch me up.I still have some scars on my left hand to remind me to never work on my multicopters with the props on.

author: peteb2
author_rank: Regular Contributor
timestamp: January 12, 2017, 10:48:36 am
content: Here's another, not directly my stupid mistake but a reminder to stay across work and projects around you when part of a team under the same employer.ON this day everyone was really busy with their current tasks at the bench. It was the 1990s and urgency was a Broadcast TV News Camera (shoulder job) that had finally had so many pixel failures on all its 3 sensors it produced pictures more akin the Milky Way. The firm decided they'd spring the almost $20,000 for a new optical block which consists of a bayonet lens mount, dichroic red, green and blue prism, filter wheel, timing PCB and 2/3" CCD sensors and amplifiers bonded to the prism such that the red and blue channel devices are half a pixel offset to the green, ( latter done to reduce aliasing in the video).The part arrived in the country and that morning there was only one person in the team of techs who'd a spare moment to swap the block out.OK, so he was the new guy who'd come to work with us recently. We all assumed he'd be familiar with the basics of a 3-sensor camera so. He was asked to just pull the old optical block and put the new one in.About an hour passed when one of the other guys asked if the camera was done because the department that used it needed it by noon. New guy said nothing so a quick look see over a shoulder was made...That's when a bit of fright set in.... there was a carefully denuded of its CCD sensors prism sitting in its shipping container and the same kind of thing in the camera!It was impossible to remount the CCD sensors for registration and the half pixel offset without the special alignment jig used in the factory in Japan and to make sure there was zero dust. The best would be a 3 image red, green, blue noisy picture.Normally it would have been unplug a few cables and unscrew a few front screws, pull the front casting and swap over!So in short we had a $20,000 paperweight and a dead camera...The firm must have done some excellent bean-counting to buy another spare but there was that long shipping delay that could not be sped up. CCDs for cameras could fail if sent by air and so had to travel by sea....We learned a lot that day how important it was to communicate with a fellow worker and perhaps to have a chat about how to knock a repair off including the proper procedure and how to check their experience or ever done it before!

author: karoru
author_rank: Regular Contributor
timestamp: January 12, 2017, 01:55:06 pm
content: Quote from: Inflex on January 12, 2017, 12:25:52 amThat's how I learned the hard way there are two kinds of these connectors with different polarities. At least most 9V batteries have awful internal resistance and it's hard to make too much smoke with them.

author: eblc1388
author_rank: Frequent Contributor
timestamp: January 12, 2017, 02:39:19 pm
content: Quote from: karoru on January 12, 2017, 01:55:06 pmNo, the polarity of the spare battery clip is absolutely correct.The fact that one mated two such clips together effectively transposed the polarity. I strongly advise anyone whose have two such battery clips would try mate them together as I did and satisfy yourself that the red lead on one is now connected to the black lead on the other.

author: Assafl
author_rank: Frequent Contributor
timestamp: January 12, 2017, 02:52:42 pm
content: Ahh - step down autotransformer. 220v input: 110v output. Pretty simple. NOT.Turned out the Chinese Manufacturer wired the plug in reverse (actually randomly). So the 110v was actually hooked to the 220v line and the "neutral" was at 110v.So still 110v? Yup - except the input protection varistors on a 110v power strip (probably 140-150V) dumped the 220v to earth.All dumped through ground - and by the time the fuse popped dispatched the magic smoke from a $700 HDMI card, the TV controller card and a 50:60Hz HDMI frame rate converter. Luckily a 10m cable protected the projector...(Oh and another 220:110v transformer decided to be pass through and fried the Roomba charger).Since then I double measure all transformer wiring.

author: senso
author_rank: Frequent Contributor
timestamp: January 12, 2017, 03:32:41 pm
content: Quote from: Powermax on January 12, 2017, 05:48:20 amWhat you need is to remember to disconnect the battery before tinkering or one day you will blow up one battery and the learn the lesson the hard way..

author: moffy
author_rank: Super Contributor
timestamp: January 12, 2017, 11:24:30 pm
content: When I was 13 or 14 with no real understanding of Ohms law I decided I would try to make a heater element. I got a solid steel bed spring (because to me it looked like a heater coil) then I got some flex with a plug on it and wrapped the wire to the coil ends. I then placed the coil on a breadboard in the lounge room and switched it on. Some minutes later when I could see again after a section of the cable vaporised I noticed tiny little spheres of copper that had burnt their way through my mothers lace table cloth. When I removed the copper spheres you couldn't notice the extra holes because the lace disguised them. Mum never knew.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: January 13, 2017, 03:30:45 am
content: When I went home for Christmas break in 3rd year university I left a few things in a locker on campus. Amongst some inconsequential stuff I left a 1942 copy of the Royal Air Force Signal Manual. It was loose leaf about 4 inches thick and bound with string and was called by one educator as "about as authoritative as you can get" on the subject of signals and electronics as of then. I got it from a friend of my dads who retired after many years working for the Canadian government writing and editing training manuals for the military. I forgot that the lockers would be emptied by the school by new years day and everything in them would be discarded. I searched, inquired, ranted trying to find it but never found where it went. I still get misty thinking about what a fool move that was.

author: Circlotron
author_rank: Super Contributor
timestamp: January 13, 2017, 04:03:49 am
content: Almost 40 years ago had an old Pontiac with a very sloppy column shift gear linkage. Went to start it one day and absolutely nothing. Gear was in R but selector showed PK and so the inhibit switch was preventing it doing anything. Popped the bonnet and put a screwdriver across the starter motor solenoid terminals. Engine springs to life at at a fast idle and a second or two later I heard the unmistakable sound of the old Powerglide auto tranny getting up hydraulic pressure and engaging... Car flew backwards across the yard and through the fence into next door's back yard.

author: karoru
author_rank: Regular Contributor
timestamp: January 13, 2017, 05:58:22 am
content: Quote from: eblc1388 on January 12, 2017, 02:39:19 pmThere are some with wire colours marked backwards - for use in power supplies, so the "color-polarity" matches one on battery, not one on the usual clip. That's what I meant:)

author: jeroen79
author_rank: Frequent Contributor
timestamp: January 13, 2017, 07:16:27 am
content: A non-electronic but stupid mistake:I was putting up some rollup curtain and took careful measurements. I then calculated that the curtain and rollbar had to be shorted by 30mm and double checked this.Then I proceeded to carefully mark off 30cm and sawed it off.I was greatly surprised when I held it up to the window.Quote from: moffy on January 12, 2017, 11:24:30 pmAs a kid I wanted to build an electromagnet I saw in a book.So I wound some wire around a nail and hooked this up to a transforer for an electric blanket. This made the magic smoke escape from the carpet in my room!I tried to conceal the mark by putting a wastebin over it. Unfortunately this did not fool my dad.

author: Cupcakus
author_rank: Contributor
timestamp: January 13, 2017, 08:18:32 am
content: I designed a pcb boost converter recently with a battery connector on one side for the low voltage, and the same connector on the other side for the high voltage. I placed the high voltage connector first, then flipped it for the battery connector but forgot to flip the silkscreen polarity marks on the part. So the boards arrived and I connected the battery backwards and it's amazing how much magic smoke one little battery can cause.

author: vealmike
author_rank: Regular Contributor
timestamp: January 13, 2017, 10:18:44 am
content: Many years ago as a young product quality engineer (yup, many years) I was asked to run a burn in cycle on a new product. The test was due to run over a weekend, the kit was somewhat expensive.Somewhat? Well it was a prototype disk enclosure, a 19" rack box with a bunch of spinning hard disks in the front and power cooling / RAID controller in the back. The first and only proto.It was loaded with a brand new drives from Seagate. From memory they were the first of that model of Barracudas in Europe. They were pre production drives, purchased at a great uplift over their already expensive planned ship cost. So, we're talking about £75,000 ish UK Sterling in the early/mid 1990s.So muggins loads the kit into the thermal chamber. The thermal chamber had its own mains outlet for powering the DUT, limited to 2KW, at 2.5KW my kit was too much for this so I plugged the kit into the mains, set the chamber to ramp rapidly from 10C to 40C and back. I connected a host PC and started random IO running to thrash the disks. Happy in the knowledge that I'd done an excellent job, I headed home for an average 20 something's weekend of alcohol and loud music.Anyone spotted the mistake yet?Monday morning, I turn up for work a little late. Its Monday, its normal. First person I see looks at me and shakes his head. Second one tells me to brace myself. When the third told me to start clearing my desk, I started to wonder if I might have cocked something up...Over the weekend, the thermal chamber had tripped. Both the heater and the chiller had cut out. Had I plugged the DUT into the chamber's dedicated power out, the DUT would have had its power cut too. But I didn't do that, all 2.5KW of DUT was powered from the mains, and kept going.Those of you who have used thermal chambers will have noticed how thick the walls of the chamber are.It turns out that there is a lot of thermal insulation in those walls. I guess you don't want heat from your lab warming the inside of the cold chamber, or heat from the chamber escaping to the lab. The latter kind of explained why the plastics on the DUT were emulating Dahli's clock.I discovered that a 2.5KW heater sealed in a thermos and left going for ~60 hours gets bloody hot.Hot enough to melt all the plastics. Hot enough for half the drives to stop working. Too hot to handle any of the parts for a good half hour after it was switched off. Chamber temperature was 115C. The DUT had fan cooling, typically we see a 50C rise between inlet (chamber temperature) and air flowing over our PSU/Controllers.I'm sure its not the dumbest thing I've done, but it is the most expensive mistake I've made.

author: Circlotron
author_rank: Super Contributor
timestamp: January 14, 2017, 02:31:34 am
content: Quote from: jeroen79 on January 13, 2017, 07:16:27 amThat bring back memories of my adventures with a curtain rail. It was 300mm too long so I went and cut off 330mm. D'oh! Off to the shop and get a new rail, measure it and then cut off 330mm asecondtime...

author: FrankenPC
author_rank: Unknown
timestamp: January 14, 2017, 04:15:12 am
content: 13 years old.My Commodore 64 monitor dies. Hey, I have a screwdriver...I wonder if I can fix it? What's that weird suction cup on the tube? I think I'll try to pry it off with my screw driver. The ensuing discharge damaged my hearing for two days and blew a quarter sized hole in my parents carpet.Well, I'm still alive at least.

author: SeanB
author_rank: Super Contributor
timestamp: January 14, 2017, 07:02:17 am
content: Quote from: Inflex on January 12, 2017, 03:25:25 amStill have the sidecutters, with the now built in wire stripper. both of them..........

author: Inflex
author_rank: Regular Contributor
timestamp: January 14, 2017, 12:34:54 pm
content: Quote from: SeanB on January 14, 2017, 07:02:17 amThat's the stuff!

author: Planobilly
author_rank: Regular Contributor
timestamp: January 14, 2017, 08:59:49 pm
content: I "ASSUMED" and that was all it took, followed by a liteiny of unwanted outcomes. LOLBilly

author: David Hess
author_rank: Super Contributor
timestamp: January 14, 2017, 09:34:56 pm
content: Quote from: SeanB on January 14, 2017, 07:02:17 amA friend made a comment to me that one room in his house had a light switch that did not work after refurbishing. I immediately suspected that the problem was likely caused by the wall socket having been replaced without removing the shorting bar on the hot side so we pulled the cover plate off and removed the socket from the wall.The only tool I had was my Swiss army knife which included pliers and while I was messing with the socket my friend asked, "Shouldn't we flip the breaker to turn the power off?" *zap* "Nope, I have taken care of it."It took a nice divot out of one of the teeth on my Swiss army pliers.

author: Codebird
author_rank: Regular Contributor
timestamp: January 14, 2017, 10:45:17 pm
content: Many years ago, I was playing with bodged-up device. It involved a step-down transformer off the mains, a rectifier, and a bloody huge capacitor bank - I was trying to spot-weld something, I think. Somehow I managed to mis-wire the thing. I'm still not sure how, but I took out all the power. To the street.I think I discharged the bank into the transformer secondary, and created a very high-voltage pulse on the mains - enough to trip a safety shutdown at the substation. Fortunately it came back up a minute later, so there must have been an automatic reset.Others:- Building a buck converter, buying a nice low-drop diode, but just assuming it was a schottky. It wasn't. It went pop. High frequency operation is not something regular rectifier diodes are made for.- Connecting a 10KV voltmeter to a 4KV capacitor bank, thinking it had an internal resistor. It did not. It went pop.- Crashing mobile phones with an EMP. Several times, before I got a camera with a zoom.- Using a 12V car headlamp bulb as a test load. Placing said test load on a wooden surface.- Not using proper eye protection when trying to make a laser lawnmower. This doesn't work, anyway - you need to evaporate the water from the grass before the laser will cut through it. I had visions of putting the laser on a turntable and sweeping it slowly across the lawn.Some friends and I dabble in high energy physics as a hobby. Our safety considerations mostly involve being in another room from the business end of things, and operating the zappy gear via a fiber-optic cable. I had to design all the electronics to be hardened against EM some of our machines can generate when firing, as it tends to crash anything too delicate.

author: Inflex
author_rank: Regular Contributor
timestamp: January 14, 2017, 10:57:43 pm
content: Quote from: Codebird on January 14, 2017, 10:45:17 pmIgnoring the obvious undulations of the land, all you need is a bigger laser... yes, thought about it myself too

author: SeanB
author_rank: Super Contributor
timestamp: January 15, 2017, 09:53:36 am
content: Quote from: Inflex on January 14, 2017, 10:57:43 pmHow about that big one Mike'selectricstuff was showing on his channel recently. might trim the lawn nicely, though the neighbours could be upset with the large holes that appear in the walls, and your electric bill would suddenly show a 3 orders of magnitude increase.

author: Inflex
author_rank: Regular Contributor
timestamp: January 15, 2017, 10:05:12 am
content: Quote from: SeanB on January 15, 2017, 09:53:36 amWould explain the power problems in ZA in the last 12 months (hope that's been sorted out now for you guys)

author: Christopher
author_rank: Frequent Contributor
timestamp: January 15, 2017, 10:14:58 am
content: My biggest mistake?Getting a job in Electronics.

author: baltersice
author_rank: Regular Contributor
timestamp: January 15, 2017, 11:14:32 am
content: I just dropped my phone in ferric chloridehttps://www.youtube.com/watch?v=GYIiOkr6x9o#t=10m9s

author: ZeTeX
author_rank: Frequent Contributor
timestamp: January 15, 2017, 01:49:50 pm
content: Quote from: baltersice on January 15, 2017, 11:14:32 amBy your video I thought you dropped your dick in ferric chloride

author: peteb2
author_rank: Regular Contributor
timestamp: January 16, 2017, 09:38:52 am
content: Going back to the days i'd a father-in-law, i watched in awe one arvo as he single handedly... survived electrocuting himself.Here in NZ we have the same mains plugs as Aussy:"Dad's" biggest hobby was his 20ft speedboat that he used purely for fishing and much of it he had built or modified. This included the crazy rear facing 'trailer' board for use during towing. It sat width-wise across the upper part of the boat and carried the rear running lights, brakes, turn indicators plus illumination for the license plate. "Dad" had wired the whole thing himself but i was not happy he had used mains plugs and sockets everywhere! I argued for weeks he needed proper automotive stuff and never to use mains connectors for anything else because muckups can happen. Stubborn old fart, knew better though.In the getup had 2 short length plug to plug (known as suicide lead) and a socket to socket 'jumpers' that joined (plugged into) into what was a backbone loom that would be run out from the rear of the towing vehicle hitch point and then connected plug/sockets on the board to power the lights.OK it worked well enough.Oneday 'Dad' was on another project, ran out his longest mains extension cord to the back garden that needed him to use the old skill-saw. That lead wasn't long enough so he then unrolled his 2nd longest extension only he ran it the wrong way round so he ended up with it's plug where the socket needed to be. No problem, the boat was sitting there on the trailer so he grabbed the two 'death leads' and adapted the ends of his 2nd extension lead.Then he picked up the skilly only to be thrown off his feet, and hurl it into the air plus yell a whole lot of obscene words. His trailer adapter leads put mains Active onto the body of the crusty shinny old alloy body of the saw. No amount of protest on my part made him chuck the entire setup away and rerun the 2nd extension lead. The obnoxious old fool simply set about changing the wires to which pins in his death leads. He just would not listen to me... a friking electronics tech at the time!Funny thing though.... Next time he went out with the boat the wrong lamps came on and he couldn't work out why!

author: steaky1212
author_rank: Regular Contributor
timestamp: January 16, 2017, 10:48:45 am
content: The top of the stairs featured a perfect spot for a bookcase. Perfect, except for the switch of a fused switched spur that fed the old immersion heater in the attic. The immersion heater had been stripped out and replaced with a combi-boiler in the kitchen so this was now redundant. So I figured that the switch could come off the wall and the hole plastered over. I switched the circuit labelled "immersion heater" off at the circuit box, removed the faceplate and checked the circuits were dead with my DMM. At this point my GF was saying "are you sure you should be doing that? Maybe we should get an electrician in?".Hey, I'm an EE and I know what I'm doing...The DMM showed 0V so I got my trusty sidecutters and BANG!! As it turned out, the DMM had a latching button for HOLD and that had been accidentally pressed, and that circuit was a spur from the sockets.I don't know what was more damaged, my sidecutters or my reputation. Needless to say, she takes great delight in recounting the story.

author: IanJ
author_rank: Unknown
timestamp: January 16, 2017, 12:04:33 pm
content: Last weekend:A mate said his cooker hood was intermittent, the lights flashed/pulsed and the fan had trouble starting.Sounded like bad caps on the control board so I went round. We powered the hood down at the fuse box, I checked no mains present at the hood and removed the control board. The caps looked ok, but decided to take the pcb away and change them anyways........I returned an hour later and went to work re-fitting the pcb........BANG!So my mate had turned the hood power back on at the fuse whilst I was away!........for the kettle or something.Ian.

author: TheAdmiralty
author_rank: Contributor
timestamp: January 17, 2017, 09:10:26 am
content: ...Welp, if you're going to make a PCB using an excessive amount of surface-mount tantalum caps, make sure you link the anode and cathode on the footprint to the proper schematic pins.It's quite a sight watching 26 significantly large tantalums all vaporize at the same time when hit with -12V. Makes sense now why they list a risk of "detonation due to catastrophic thermal runaway" when overvolted into a short, though I'm not sure reverse polarity really applies to that.I've developed a bad habit of double-checking everythingaftera run of prototypes have been sent in for fabrication. I wouldn't recommend it at this point.

author: Cyril.Anthony
author_rank: Contributor
timestamp: January 17, 2017, 12:05:48 pm
content: When i was a noob i thought the marking in tantalum capacitor signified negative like in the electrolytic capacitors. lol i was soo wrong that small 22uF capacitor blew like a fire cracker

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: February 06, 2017, 08:05:28 pm
content: If you want to talk about expensive mistakes...Some decades ago I worked for a small (5-7 employees) broadcast video manufacturer in Toronto and as I was the resident technical knob there, I was given the task of organizing the manufacture of 50 new copies of a standard product of ours, a time code reader with a lerge 2-sided board. The pcb layout was done as two-colour tape on a polycarbonate film which was then photographed and colour-separated to produce the master production negatives for the PCB fab shop. These films happen to have no textual info on them except silk screen legend. I got the boards underway and then bought all of the parts and when they arrived got the girls to assemble them. My boss decided he would try out one of the first to be ready.The board shop assigned the top and bottom negatives of the copper layers at random, assuming it didn't matter and went ahead with it. This wouldn't have mattered to the operation of the circuit except that there was an edge connector on it. A big one. All of the top-side pins and bottom side pins of that edge connector were swapped and proved to be unfixable making the entire run of boards scrap. We lost a lot of money and 6 weeks in that screw up which could have been avoided in about 1 minute of correctly marking the artwork with a sharpie.My job survived but not by much.

author: raptor1956
author_rank: Frequent Contributor
timestamp: February 06, 2017, 09:16:28 pm
content: Many moons ago, while working as an Avionics Tech in the USAF, I was working on a panel light on the instrument panel and since it was 28VDC I didn't feel any need to power it off first. So, I grab the thing and am working on it and I leaned in and my upper lip touched the yolk. The 28VDC went into my hand, through my body, and exited through the contact patch my lip made with the yolk -- it felt like someone jammed a knitting needle through my lip -- f'n hurt like hell!So, don't mess with 28VDC.Brian

author: eugenenine
author_rank: Frequent Contributor
timestamp: February 06, 2017, 09:45:46 pm
content: I did similar but it was the strip the wire with your teeth on a telephone ring generator that I thought was not powered on.

author: ptricks
author_rank: Frequent Contributor
timestamp: February 07, 2017, 12:00:33 am
content: I cut the end off a usb cable and assumed red was positive and black was negative.Apparently china doesn't care about wire color, I let the magic smoke out on a very expensive circuit due to reverse polarity on the wires.

author: meeko
author_rank: Contributor
timestamp: February 07, 2017, 07:18:40 pm
content: Maybe not the stupidest, but probably the biggest bang I've made...Taking electronics in high school, the lab had a big power distribution panel, that fed 120V/15A AC, variable AC and variable DC (the same voltage to every desk) to all the desks. Then each desk had a grounded metal box with the various connectors.We were building a mains lamp flasher, with a 555 and a relay. The lamps were powered from pigtails plugged into the 120V outlets, with bare wires that we hooked onto with alligator clips. I bumped my mains wiring, and the hot came too close to the side of the power box, with predictable results--a flash and a bang. There were individual breakers for each desk, but I guess only 1 GFI on the input to the distribution panel, and that was what tripped, so I knocked out everybody's power. Whoops...

author: dimkasta
author_rank: Regular Contributor
timestamp: February 09, 2017, 02:58:16 pm
content: From an early age I exhibited a tendency to take apart and "fix" anything around my house that we did not necessarily need anymore.All I needed was my screwdrivers and my tongue firmly attached to the right side of my upper lip for extra concentration.The scariest thing I ever did (not realizing it then of course) was taking apart my grandfather's tube radio. Fortunately, it seems I was lucky enough to never touch any capacitorsAnd the second one was to connect an old washing machine motor directly to mains to see if it would turn. Fortunately for just a split second.I always was a fraidy-cat with mains voltages, and thank God for that. I have a few melted test-screwdrivers as a reminder that it's always right to be paranoid about mains voltages.It's the same thing with guns. It is the empty/safe ones that kill.

author: eugenenine
author_rank: Frequent Contributor
timestamp: February 09, 2017, 03:26:48 pm
content: the washing machie motor reminds me. We picked up a treadmill from the curb and it has a 90vdc motor. I showed my son how to colder up a bridge rectifier so we could test the motor from mains. He soldered it up and was ready to plug it in as I was yelling 'wait'. The big flywheel was heavier than the motor so the motor started turning at full speed winding the wires around it as it pulled the plug back out of the wall and his hand. he took off running as fast as the cats did.

author: Tom45
author_rank: Frequent Contributor
timestamp: February 09, 2017, 04:18:33 pm
content: Hard to say what my stupidest mistake might have been, but a memorable mistake was when I set my house on fire.Nearly 60 years ago when I was a kid experimenter, I built a Jacob's ladder using a neon transformer in my basement workshop. It worked quite well. Then, leaving it on, I went upstairs to get a snack. While eating I smelled smoke. Ran downstairs and found my workshop on fire. The arc had set some nearby paper on fire. I managed to get it put out before the fire department arrived.Wikipedia has the following in their article on Jacob's ladders:Traveling-arc devices are dangerous. The sparks can burn through thin paper and plastic and start fires, and contact with the exposed high-voltage conductors can be lethal.[citation needed]Citation needed?I didn't stop to think about the possible fire danger although I was well aware of the high voltage danger. But if someone had told me at the time that there was a fire danger I surely wouldn't have said "I don't believe it. What is your source?".

author: Codebird
author_rank: Regular Contributor
timestamp: February 09, 2017, 04:46:47 pm
content: QuoteI've read those are good motors for using as dynamos in DIY wind turbines.

author: eugenenine
author_rank: Frequent Contributor
timestamp: February 09, 2017, 04:54:27 pm
content: Quote from: Codebird on February 09, 2017, 04:46:47 pmThats what I've seen too. Going to put one up beside the cabin someday.

author: 8086
author_rank: Super Contributor
timestamp: February 09, 2017, 04:56:57 pm
content: When I was about 5 years old, I put a lemon shaped soap into a lamp fitting.Luckily, it was off.

author: meeko
author_rank: Contributor
timestamp: February 09, 2017, 06:53:03 pm
content: Quote from: 8086 on February 09, 2017, 04:56:57 pmDoesn't really count, as it was in a role-playing game, but one time a (female) character I was playing seduced the "big bad's" right-hand man, had "relations" with him then, when he fell asleep, killed him by jamming a certain lower-body appendage into a lamp socket and turning it on. Yeah, that character was kind of messed up...

author: LaserSteve
author_rank: Super Contributor
timestamp: February 09, 2017, 07:26:06 pm
content: Four foot long, brand new glass-ceramic Krypton Ion Laser Plasma tube with gas ballast attached by 6" stainless steel corrugated flex line to the plasma tube/... Was installing it into its water cooled magnet. My helper had a muscle spasm.. My boss heard me yelp when the flex line cracked. Near tears, thinking my job was over due to 7500$ loss, heard, in deep Russian accent, "You have served us well over many years, you get a mistake once in a while. Personally drive to the factory in St. Louis and pick up another one, see it running there. The purchasing paperwork will be done before you arrive. Install it yourself, like you usually do without the helper and be back here in three days, I have research to do..." I could not believe my ears... I set a new record for Cleveland to St. Louis, installed a new one there, and set a new record for slowest drive with a fragile object on the way back...Steve

author: eugenenine
author_rank: Frequent Contributor
timestamp: February 09, 2017, 09:58:18 pm
content: Quote from: meeko on February 09, 2017, 06:53:03 pmYea, sure, it was the characters idea.

author: Deridex
author_rank: Regular Contributor
timestamp: February 20, 2017, 11:52:50 am
content: my most stupidest mistake is something i did quite a few times:I did not check the voltage of a powersupply despite the fact that i knew it was unrealible.Result was: smoking stuff on boardsAt least my coworker roasted a few boards that way too...

author: RoGeorge
author_rank: Super Contributor
timestamp: February 20, 2017, 12:30:13 pm
content: https://hackaday.io/project/7590-retardo-davinci

author: TheWelly888
author_rank: Frequent Contributor
timestamp: February 20, 2017, 01:32:46 pm
content: Touching the metal tab of a switching FET on a live SMPSU, fortunately it was running from an isolated 115V source!

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 20, 2017, 02:57:55 pm
content: I just spent three weeks procrastinating on a project because I couldn't find a 5 position rotary switch because the 12 way one I have has too many positions(for those who don't know, there is a little latching bar you can adjust the travel to any number between 2-12 positions)I've only been using these switches 20 years and never even noticed it until 5 minutes ago.

author: dimkasta
author_rank: Regular Contributor
timestamp: February 20, 2017, 07:07:25 pm
content: Which reminds me...Can's say if he's trolling or if he's just plain stupid...

author: kolbep
author_rank: Frequent Contributor
timestamp: February 20, 2017, 07:28:03 pm
content: My Most Stupid (and Costly Mistake), Warning, EXTREMELY CRINGEWORTHYCustomer supplied a decent size Variable Speed Drive (Inverter) for one of their Oil Circulation Pumps (A large Oil Factory).Ok, So install an outdoor enclosure, isolator, run the 3 Phase 400V Supply. Then check that the Inverter supply must connect on the bottom right of the Inverter, with the Load on the bottom Left. Ok? that seems opposite to convention. Double Check it according to the Manual, yep that is the way it is supposed to be.Guess What I do? Yep, Even after double checking, I went and hooked the supply up to the left, and the load to the right.Switch on the Isolator, and there are Sparks, Flames and Smoke. Completely destroyed the Output Stage of the Inverter, as well as the main control board. ZAR15000 Later for a new VSD, I have learned my lesson. I now check it 5 times, and also have my helper double check...

author: rs20
author_rank: Super Contributor
timestamp: February 20, 2017, 09:25:00 pm
content: Quote from: Deridex on February 20, 2017, 11:52:50 amSounds? to me like the stupidest thing here was not discarding/fixing the supply after incident #1...

author: Matthew98
author_rank: Regular Contributor
timestamp: February 20, 2017, 10:23:45 pm
content: I guess when i was a kid...I salvaged some 5V motors from rc cars and made alternatve cars with them (like attaching a blade to a motor and let the car blow away.... yeah..)) ) anyway one day, when 9V battery went flat i was like : Man, how am i gonna make the motor spin faster ? and than i saw mains plug in front of me..... It blew me away with sparks all over the place))) from than im very careful with mains...

author: Cubdriver
author_rank: Unknown
timestamp: February 22, 2017, 06:36:45 am
content: Quote from: Tom45 on February 09, 2017, 04:18:33 pmNot my mistake, but a friend's brief shining moment of sheer idiocy. Back in my late teens/early 20s I had some friends over (not a particularly technical bunch, but all in college, mind you, so expected to be at least somewhat smarter than a sack of hammers) and was showing them a Jacob's Ladder that I'd made up with some coat hanger wire and a 10 kV oil burner ignition transformer. The ladder was about 14" tall and opened to perhaps 3" wide at the top. The nice fat blue spark was starting at the bottom and merrily climbing before splaying out at the top and extinguishing, as Jacob's Ladders do.I had just shown them how the spark would ignite a piece of paper held in its path. A mere moment after this demonstration, one of them says "If I put my hand in there, will I get a shock?", and before I can process and react proceeds to stick his hand between the wires and in the path of the rapidly ascending spark. Needless to say, he removed his hand very quickly and then spent some time attempting to massage some feeling back into it. All I could say was "I dunno, George - it's a 3 inch long spark, and you just watched it set a piece of paper on fire. What doyouthink will happen?!?"Going on 30 years later I still occasionally bust his balls about that little stunt.-Pat

author: obiwanjacobi
author_rank: Super Contributor
timestamp: February 22, 2017, 10:04:40 am
content: Fresh out of school, first job. We had renovated an elctro-mechanical cigarette vending machine to support a new dutch 5-guilder coin (before the euro) and the price of a pack of cigarettes had rissen above the amount the electro-mechanical step-counter could count.So we ripped out the counter and some other relais we no longer needed, outfitted it with an electronic-coin reader (one of the specialties of the company I worked at) and added a 2x16 LCD and an 68HC11 micro - this was 1992.After we managed the reverse voltages and spikes that we flying around in the cabinet, it all worked fine. I had almost filled the 4k flash with the program to control it all.The customer was very content and went of to put his vending machines in the field. Of course there were some small bugs still in there, so a new version of the software had to be made. We tested it on the vending machine we still had in our shop and sent him the new chips (he would return the old chips).A couple of days later he called and said that some-one had emptied out a couple of his machines. Turned out that my recent changes in the software at opened up a 'security hole' that allowed you to make the vending machine to repeatedly output cigarettes while only paying once by locking the mechanical select buttons.That was the worst I have ever felt, I think. I felt so responsible. Luckily I found the bug quickly and we could send out the fix the same day.It tought me a valuable lesson about software/hardware testing.

author: SingedFingers
author_rank: Frequent Contributor
timestamp: February 22, 2017, 02:55:02 pm
content: Today's fuck up. Hmm not 0.1" pitch!Nope didn't read the datasheet before I bought 20 of these ... at least I've got some SMD protoboards now!

author: fuzzoli
author_rank: Regular Contributor
timestamp: February 23, 2017, 10:15:51 pm
content: 20 years or so ago, we were working on code which screen scraped mainframe 3270 screens. I had several terminal windows open when the conversation went something like this:Coworker: Why did you just shutdown the Production window?Me: No, I didn't.Coworker: Yes, you did. Look at the server name.Me:AFTER fixing the problem, I went into my boss's office and explained what I just did.Fortunately she understood, but mademewrite and send the email to our business partners explaining what happened.Ever since then, I have a code I live by:Anything Dev (terminal windows, etc.) isGreen.Anything Test isYellowAnything Stage/PreProd isOrange(ish)andAnythingRedmeans "Think VERY carefully before pressing Enter!"I have never taken down Production since.

author: nidlaX
author_rank: Frequent Contributor
timestamp: February 23, 2017, 10:37:22 pm
content: My most recentmoment was spending 10+ hours on a Fluke 199C probing test points, measuring components, looking for signs of physical damage, and poring over schematics when the problem was that I forgot to increase the current limit on my power supply, thereby preventing a complete power on.It's helpful to make sure the instrument is actually broken before attempting a repair.

author: eugenenine
author_rank: Frequent Contributor
timestamp: February 24, 2017, 12:20:50 am
content: Quote from: fuzzoli on February 23, 2017, 10:15:51 pmI had a hung backup server back in the days of mechanical power switches. I had to call my cow-orker from the server room and ask him to have everyone close outlook because I pushed the button on the exchange server by accident. I realized it as I was pressing it so as long as I held it in the exchange server had power but it had already clicked so as soon as I released it it was going off.

author: rs20
author_rank: Super Contributor
timestamp: February 24, 2017, 12:55:58 am
content: Quote from: fuzzoli on February 23, 2017, 10:15:51 pmWait, you have a production service running in a terminal window, and just closing that terminal window kills the service? Or did I misread?

author: fuzzoli
author_rank: Regular Contributor
timestamp: February 24, 2017, 02:07:40 am
content: Quote from: rs20 on February 24, 2017, 12:55:58 amNah, closing the window wouldn't have done any harm. Back in the day before web services and APIs, the only way to get data off the mainframes was to scrape data from a terminal. There was software which emulated 3270/5250 screens, let you wait for certain characters at certain positions, and then "scrape" off the data you needed. One of the tools let you watch the window as the app traversed the screens. Part of the toolalsolet you reset and restart the windows (for when things got confused). That was my downfall. I thought I was restarting the development system, but since the development team also did production support back then, I had prod windows open too. Oops!

author: Tom45
author_rank: Frequent Contributor
timestamp: February 24, 2017, 04:56:57 am
content: Quote from: eugenenine on February 24, 2017, 12:20:50 amHolding that button sounds like the Dutch boy with his finger in the dyke.

author: Sjoertdb
author_rank: Contributor
timestamp: February 24, 2017, 11:04:55 am
content: One of mine:Not supporting a supply from the programmer simultaneously with the main supply

author: steaky1212
author_rank: Regular Contributor
timestamp: February 24, 2017, 12:39:43 pm
content: Quote from: eugenenine on February 24, 2017, 12:20:50 amI used to do this to my brother when I wanted to go on the computer. If you were quick you could release the button and press it again without the computer going off.

author: JenniferG
author_rank: Frequent Contributor
timestamp: February 25, 2017, 11:22:57 am
content: My stupidist mistake was when I was about 11 years old and decided to cut a lamp cord with diagonal cutters while still plugged in. Made a few burn marks on my hand, gigantic arc and scared the heck out of me. I HAVE no clue to this day why I did such a thing!

author: Zbig
author_rank: Frequent Contributor
timestamp: February 25, 2017, 12:29:25 pm
content: Quote from: JenniferG on February 25, 2017, 11:22:57 amI once ordered some dubious quality RC Li-Po packs, 3S 1800 mAh or so. Some of them arrived pre-puffed already so I decided to scrap them, salvaging the heavy-gauge wires and plugs first. I stumbled upon my dad so I asked him to grab his heavy duty shears and cut the wires. I only managed to say something like "but carefully; one by one, don't short them as they're capable of delivering quite some cur... BLAST!!!" He looked surprised even thouh he's not really that easily impressionable.

author: SeanB
author_rank: Super Contributor
timestamp: February 25, 2017, 05:47:50 pm
content: When I was very young, I wanted to light up a flourescent lamp starter like a neon lamp. So, take one old starter, and look around at the plugs, and decide the 5A socket outlet adaptor will fit the prongs nicely, so put it in there, and then turn on the power.Instant conversion of the lamp to nothing, only the base left there on the floor where it landed, and the dog did a fair imitation of a bullet and vanished to far away. Go to the laundry, where Dad had installed the new fangled at the time ( it came from Australia, complete with 2 Australian socket outlets and 2 rewireable plugs for them) RDC and breakers, which he had fed from the fuse box ( yes, old houses here still have fuses in some, only thing that has to happen with a sale or any electrical work is RCD installation, which often results in a rewire because DCC wire really is leaky, some cheapskates only replace the live with PVC as well and leave the DCC neutral as well, which is crap) using a good length of Pyrotenax cable. Reset the breakers, check the lights still worked, checked pants for more skid marks and ( with the power switched off) swiped most of the copper stain away from the 5A adaptor.Never found anything more than the bakelite base, with the melted pins, and half a capacitor in the pins and no capsule, or it's wire leads. I must have been around 7 at the time, as I was at primary school down the road. no driving there, we all walked every day, wet days with a raincoat. Fun days playing in the bush and at the local river.

author: tautech
author_rank: Super Contributor
timestamp: February 25, 2017, 08:40:29 pm
content: Personally I have a lot to that my father for, he was a farmer but in his youth had a passion for Shortwave, built his own valve receivers and listened to shortwave stations from all over the world, this was late 40's and early 50's. Farmers were a resourceful lot having to fix and maintain all manner of their own plant due to their remoteness from service and repair facilities. He had a small but adequate kit of gear and all manner old old stuff in the sheds which was gladly offered to the young enquiring minds to keep us occupied rather than get under his feet.After a few stern words about not losing any of his tools and an insistence to return them to where we found them we were off into the big boys world of fixing stuff.IIRC my firstpatientwas a Villiers MK 10 engine that was quickly spirited home to the basement where I could tackle with gusto. Some infrequent supervision followed with instruction that it MUST have spark, fuel and compression in order to run. So of course a cocky younster must tackle the most difficult first....spark.Off came the covers and cowlings to expose the flywheel, under which were the ignition points, that of course must be mandatorily cleaned.On the Villiers flywheel there was a cover plate and when removed you could look through between the 3 spokes of the flywheel to see the ignition points housing which was covered by another cover plate and once removed you can see, clean and adjust the points.Not knowing how to proceed I marvelled at the workings in detail, rotating the flywheel too and fro by hand while watching the points open and close and lining up with the timing marks and the piston reaching top dead center.ZAPEven at such a young age (under 10) I instantly had great respect for electricity and steps that heeded to be taken to keep one safe. That Villiers never bit me again and for a short while later in my teens I worked on all manner of small motors for a living.Back to the Villiers, Dad showed me how to remove the flywheel, these old Villiers where great in this respect with a captured flywheel nut that when undone pulled the flywheel from the crankshaft taper.Cleaned the points and was rewarded with a nice spark with a yank on the starter cord.Then came the carburetor which of course must be duly removed and dismantled and inspected in great detail.Finally it was all ready to be reassembled and a start attempted......I couldn't wait.Spark, check.Petrol, check.First pull.....nothing, OKSelect full choke.Second pull.....Yiha, flick choke off..........holy hell, off at full revs....I mean FULL revs.Shite, I wish I'd mounted this motor on something it was dancing all around the concrete floor of the basement.How many things rush through your mind when things go bad still amazes me but quickly I realised in my haste to get it running I'd left the speed governor linkage loose.Young as I was, I just had to man up and grab the thing and press the stop button....The racket had stopped and I was safe now.I still remember how hard my heart was beating 50 yrs later.Hell look at all those marks on the basement concrete floor.....what can I do to tidy thoseah, broom a little dirt over them.Yep all kids will try and hide their mistakes.Just got things sort of tidy and mum appeared wondering what all the commotion was.Who me? I was a little angel.Problem identified and fixed....ten minutes later after double and treble checking the governor linkage I had it running like a Swiss watch.What will be the next victim.....me, that's another story.

author: Cubdriver
author_rank: Unknown
timestamp: February 26, 2017, 09:15:28 am
content: SeanB's reminds me of one from high school. I came across some geared synchronous motors in the supply crib, and found that if I held the output shaft tightly enough, I could turn it and spin the motor. I also had on hand a few NE-2 lamps. I got curious, and connected one of the neon lamps to the motor leads and noted that the motor could act as a generator, and because of the reduction gearing twisting the output shaft would spin it fast enough to put out sufficient voltage to light the neon lamp. I wandered about the shop showing friends for a while, and then got curious as to exactly how fast 4 RPM actually was (this was the speed noted on the motor's dataplate). Without further ado, I stuck the stripped lead ends into a 120V mains receptacle. (Note that I never mentioned a series resistor for the neon, nor have I said anything about disconnecting it from the motor leads. I was aware that neon lamps needed dropping resistors, but not really fully conscious of the reason why, I suppose.)As the leads went into the socket, my failure to disconnect the neon lamp was almost instantaneously rectified as it flashed very briefly and then with a pop turned into a rapidly expanding ball of tiny crumbs of glass shrapnel and, I suppose, vaporized metal from the electrodes. Fortunately I wore glasses, as my nose was about a foot away as I leaned over the bench to plug it in. They protected my eyes, and I had only the slightest flash burn on the back of my thumbs, which of course were holding the ends of the motor leads an inch or so from the space that a split second earlier been occupied by a lamp. Luckily for me, the teacher did not notice the incident, so I avoided getting in hot water for it. It definitely emphasized the low resistance presented by ionized gas, and I have not since connected a glow lamp without an appropriate series resistor.We later had great fun zapping each other with the motor, and when the basic electronics teacher (we were seniors at the time; he taught the freshmen and sophomores) found out what we were up to actually got his 2nd year students to line up and form a series circuit by touching one another, and he then zapped the whole lot of them in one shot. He was pretty cool, and was hands down the best teacher I ever had.-Pat

author: Cubdriver
author_rank: Unknown
timestamp: February 26, 2017, 09:49:46 am
content: Quote from: JenniferG on February 25, 2017, 11:22:57 amYou wanted wire strippers, likeRIGHT NOW?I made one of those, too. On the blade of what alreadywasa wire stripper.Lessons learned - sometimes there are multiple power sources feeding a switchbox, especially when it contains (4) 3 way switches and controls lights in the basement AND the garage (and was wired 50 odd years ago by your father and his drinking buddies). It is prudent to ensure that ALL of them are turned off before doing electrical work at 1:30 AM.Extra credit lesson - doing electrical work at 0130 when exhausted is not a good idea, as 'prudent' sometimes falls by the wayside.Also worth noting - making cutters into strippers in this fashion will also shut off the power source that was missed. It will also, at least temporarily, cause the exhaustion to go away.-Pat

author: grumpydoc
author_rank: Super Contributor
timestamp: February 26, 2017, 01:25:15 pm
content: Quote from: fuzzoli on February 23, 2017, 10:15:51 pmBTDTIn my case I was the victim as well as the perpetrator - I was on holiday and had logged into the home email server via SSH and VNC. Having finished the admin work I wanted to do I went to shut down my laptop, only to realise I was still looking at the remote VNC session full-screen so when I chose System->Power Off, it was the server, not the laptop. Oops.Managed to get the neighbour who was babysitting the cats to restart things.My most expensive mistake recently was actually woodworking at which I'm hopeless anyway but fitting a new worktop and sink I carefully measured (repeatedly, in case of error) the length I needed and then proceeded to cut a £170 ($215) piece of wood 10cm too short.Because of the orientation of the tape I was looking at the markings upside down and subtracted from the nearest 10cm mark rather than adding.On the subject of tapes and rules in the UK it's pretty common to get them marked in imperial and metric. They are invariably marked on both sides such that all the zero's are at the same end and, if looking with inches at the top, then flipping the rule over bottom edge over top (thus keeping the zero end in the same place) they arestillmarked with inches at the top.Why FFS? I can think in either inches or cm as things require but sometimes the orientation of the job/ruler/edge means you can only get one scale in the right position to make an accurate measurement. If that is the "wrong" units for how I want to work at that precise instant I would like to be able to just flip the ruler to get the "right" units but nothing I have found is marked so as to allow this.

author: testian
author_rank: Regular Contributor
timestamp: February 28, 2017, 10:39:34 pm
content: I was building a pwm circuit with a microcontroller (28-pin DIP) on Stripboard.Everything finished, tested and it is working. Then I disconnected the circuit from the power supply without switching it off. Put my circuit back on the table directly on the non insulated banana plugs -> magic smoke escaped.

author: Luminax
author_rank: Regular Contributor
timestamp: March 01, 2017, 12:15:56 am
content: Made a few short jumper using leftover LED legs... shifted a few jumpers around etc, change circuit layout etc...And then my PIC stopped working... and I smell... MAGIC SMOKE!one of the pin had fell off the top bench and accidentally lodged itself magically in the breadboard... shorting VCC and one of the I/O pin and boom(well... no boom... and no camera capture sadly)

author: mclemens1969
author_rank: Contributor
timestamp: March 02, 2017, 06:18:04 am
content: I break things now and then.1) I smoked my uCurrent on the first use. Still not sure how this happened.2) I fed 12V to a $95 electroluminscent display for its 5V supply. That was the last time I used a red lead for misc. V+ from the power supply. It made smoke immediately, and included a celebratory noise.3) I was pushing a $30 OLED into a breadboard (1x20 header) the other day and didn't keep even pressure enough -- snap right down the glass.4) About 20 years ago I wrote the software in a robotic FDA approved orthopedic bone lengthener. One of the movement rates and rhythms available was later found to be wrong. I forget how wrong.5) About 35 years ago we hacked into the school district computer. We kept dialing in even though one day all the access numbers (except for a single one) started being busy all the time. And why do you think only one number was left working??

author: Rerouter
author_rank: Super Contributor
timestamp: March 02, 2017, 08:38:59 am
content: 5Your telling me honeypotting was done back in the days of dialup? By school admins?4 sounds very interesting.

author: dimkasta
author_rank: Regular Contributor
timestamp: March 02, 2017, 12:48:05 pm
content: I had just dismantled an old washing machine, and I had found a nice small but beefy motor on the mechanical program rotor. It would be a nice addition to my scrap box.After a while I got bored and went to watch some Thundercats, having the motor on my hands, clicking it bit by bit just for fun.Now, this was deep summer. And here in Greece deep summer means you are sweating a lot, and when you are watching cartoons you are probably just wearing your underwear.So here I am watching Lion-o, feeling extra happy from the nice clicking sensation. It did not register on my brain that the wires were touching my belly until I decided to give the motor a big fast spin...I jumped almost a meter high, and the motor flew off my hands landing on the other side of the room.And yes we spent the rest of the week with my friends zapping each other

author: GarthyD
author_rank: Regular Contributor
timestamp: March 02, 2017, 11:33:31 pm
content: Early on while still learning, I reorganised part of a circuit on a breadboard and inadvertently flipped VCC and GND on a temperature sensor.One trick I had read about and used repeatedly when testing temperature sensors was to press your finger firmly onto the device, which will cause the reported temperature to rise slightly.Little did I realise that when left alone for a while with reversed polarity, the temperature sensor I was using got very, very hot.So, whilst debugging my code which had suddenly stopped working, I pressed my index finger firmly onto the burning hot device.Lesson learned.

author: meeko
author_rank: Contributor
timestamp: March 03, 2017, 10:19:36 pm
content: Just remembered another one from back in my high school electronics days...We didn't have proper stands for the soldering irons, just a bit of stamped metal to prop the element on to keep it off the bench.One day, I was soldering up a project, went to pick up the iron after placing my next component, and ended up trying to pick it up by the element! And not just brushing a finger against it, or anything. This was a full-on, close your whole hand around it, grab. I highly recommend avoiding doing that...

author: ohdsp
author_rank: Contributor
timestamp: March 03, 2017, 10:37:31 pm
content: I couldn't get the circuit in the attached schematic to work for some reason, spent ages building up 2 PCBs as well!

author: eugenenine
author_rank: Frequent Contributor
timestamp: March 03, 2017, 10:46:53 pm
content: Quote from: meeko on March 03, 2017, 10:19:36 pmDid that one myself. Promptly went out and bought the $30 stand one from radio shack and took it to school when we needed to solder.

author: David Hess
author_rank: Super Contributor
timestamp: March 03, 2017, 11:18:19 pm
content: Quote from: meeko on March 03, 2017, 10:19:36 pmI can do better than that; I reached over the iron which was lying on the bench and set the soft part of the inside of my arm down on the thick part of the barrel ... and it stuck. 30+ years later and I can still see the discoloration where the scar is.

author: eugenenine
author_rank: Frequent Contributor
timestamp: March 04, 2017, 12:00:21 am
content: How many of you, when first starting out. would get too much solder on the tip then flick it off?I dropped a big ball of solder on my legWas wearing shortsI'm over 40 now and can still see the scar.

author: cheeseit
author_rank: Regular Contributor
timestamp: March 04, 2017, 12:37:23 am
content: 25 years ago as a kid I was using an iron where the stand was a short length of steel tube held in a vise. While reaching over it the underside of my wrist came to rest on the tube, however shortly, resulting in the familiar sizzling sound and a smell of burned skin left on the tube. It hurt like hell and the scar is still very visible.

author: dimkasta
author_rank: Regular Contributor
timestamp: March 04, 2017, 10:06:09 am
content: I have done the same full hand grab on my first iron.Thankfully it was one of those with the plastic cover which I used when soldering too. The pain was intense but thankfully there was no sizzling or scar

author: grumpydoc
author_rank: Super Contributor
timestamp: March 04, 2017, 10:10:11 am
content: Quote from: eugenenine on March 04, 2017, 12:00:21 amNot electronics but I was soldering a capillary plumbing joint last year where the angle of the pipes, walls and joint meant that I was holding the blowtorch directly under the joint.Unfortunately I over-filled the joint and the excess dripped out of the opposite side.All over my handLead free as well (no choice with EU regs).

author: @rt
author_rank: Super Contributor
timestamp: March 05, 2017, 08:54:06 am
content: Opening 90% of webpages that say they provide datasheets

author: djacobow
author_rank: Super Contributor
timestamp: March 05, 2017, 09:04:58 am
content: Quote from: @rt on March 05, 2017, 08:54:06 amHa ha. I know the feeling. When I'm looking for a datasheet and the link isn't to the actual manufacturer's site, I only click if I am in deep desperation. And I am never rewarded.Honestly, I wish there was a Google option to tell it never to show me those sites ever again. They're Lucy with the football.

author: tautech
author_rank: Super Contributor
timestamp: March 05, 2017, 09:37:58 am
content: Quote from: @rt on March 05, 2017, 08:54:06 amUse: device data pdfCuts down on the false hits.

author: Rerouter
author_rank: Super Contributor
timestamp: March 05, 2017, 09:43:49 am
content: At the bottom of the google search page is the option to "send feedback" if we hit the BS sites enough they should be deranked off the first page.

author: ale500
author_rank: Frequent Contributor
timestamp: March 05, 2017, 09:54:57 am
content: I don't remember if it was late at night or no, but what I remember is:I had this Brazilian TK85 (ZX-81 clone but with a discrete ULA), I though I'll remove the regulator (7805) and power it directly with 5V. I didn't know it needed 12 V for the DRAMs. I was using a switching power supply with several outputs, -5, 5 and +12, that where more like 14 V. Of course I powered it with 14 V instead of 5. The noise the ICs did when they melted is something I haven't forgotten. It was 27 years ago...

author: BradC
author_rank: Super Contributor
timestamp: March 05, 2017, 01:50:15 pm
content: Quote from: grumpydoc on March 04, 2017, 10:10:11 amI got so sick of capilliary plumbing I bought a small (tiny) oxy-propane setup. Now all my plumbing is silver-soldered. No drips. Having said that, when you heat up a copper tee to a nice red heat to un-solder it, then drop it on the floor and tread on it in bare feet the smell of burning skin is pretty overwhelming.

author: grumpydoc
author_rank: Super Contributor
timestamp: March 05, 2017, 02:18:22 pm
content: Quote from: BradC on March 05, 2017, 01:50:15 pmFrench plumbers (as this escapade was in France) tend to hard solder everything and often fashion joints manually - all beyond me at the moment. Thankfully capillary fittings are easy enough to find.It sounds as though you would fit right in with the "proper" way of doing things.

author: ZeTeX
author_rank: Frequent Contributor
timestamp: March 05, 2017, 08:28:16 pm
content: I once had this great idea in 3AM to experiment with high current through a coil to see if I could heat it up nice.. yeah whatever I did I managed to get a burning mark from a 5W red hot resistor, then from the panic drop the resistor to the ground then step on it with bare feet while it is still extremely hot. and somehow I also got other burning mark from something else the same day.best day ever.

author: fable
author_rank: Regular Contributor
timestamp: March 05, 2017, 09:43:10 pm
content: When I was a boy

author: Cubdriver
author_rank: Unknown
timestamp: March 05, 2017, 10:46:34 pm
content: I bet you only did THAT once!!-Pat

author: bsudbrink
author_rank: Frequent Contributor
timestamp: March 06, 2017, 07:28:18 pm
content: Early on, I got a bag full of mixed LEDs that were "not all guaranteed to work." I sat down with a 9 volt transistor radio battery, quickly tapping the leads of the LEDs to the terminals of the battery... no current limiting resistorBlink, good, no blink, bad. I got away with it for a while. Then I was distracted for a few seconds with the LED touching the terminals. It popped like a little fire cracker. I was picking bits of red plastic out of my thumb and finger for several days after.

author: Tom45
author_rank: Frequent Contributor
timestamp: March 06, 2017, 09:25:19 pm
content: Quote from: bsudbrink on March 06, 2017, 07:28:18 pmAfter your test, they would have been "all guaranteed not to work".

author: bsudbrink
author_rank: Frequent Contributor
timestamp: March 06, 2017, 09:33:39 pm
content: Quote from: Tom45 on March 06, 2017, 09:25:19 pmSurprisingly, no. I used a number of the ones that passed my "tap test" in various projects. They all worked fine. We're talking big old 1970's "top hat" LEDs.

author: bji900
author_rank: Contributor
timestamp: March 06, 2017, 09:34:54 pm
content: Quote from: bsudbrink on March 06, 2017, 07:28:18 pmKinda like the proverbial fuse tester I knew it was a good fuse...

author: m98
author_rank: Frequent Contributor
timestamp: March 06, 2017, 09:41:59 pm
content: Once I did kind of a show demonstration of high voltage and plasma physics, also consisting of a demo of lowering the breakdown voltage of air by ionizing it with a flame. Well, guess who ended up throwing a bunsen burner a few meters across the room? At least nobody slept in during that presentation anymore...A less dangerous one, never trust in the correctness of late-night designed PCBs. Just finished assembling a board where I forgot to add output capacitance to a linear regulator, noticed the mistake as some ICs released their magic smoke.Also an all time favorite, mismatched LED-Datasheets and subtle pinout variations in jellybean parts.

author: dimkasta
author_rank: Regular Contributor
timestamp: March 14, 2017, 02:32:41 pm
content: Spending hours staring at a PCB and schematic verifying you missed nothing.Then notice a mistake on PCBs or think of a new awesome feature a few minutes after submitting the gerbers for the prototype.And then just start spamming emails in a hurry hoping that you are lucky enough to not have any issues with time differences and manage to find someone to update the files before production begins.

author: pix3l
author_rank: Regular Contributor
timestamp: March 14, 2017, 03:07:32 pm
content: Rotary switch of my Multimetrix DMM220 was broken. Opened it: plastic part that it is connected to was broken. So I 3Dprinted a small replacement part and glued it in with superglue, reassembled multimeter. But then when I turned it on to measure V(DC) it was in the wrong mode. So always double check the orientation of your parts before you glue them in

author: tkuhmone
author_rank: Regular Contributor
timestamp: March 14, 2017, 03:44:53 pm
content: When I was small kid, I used to be outside helping my parents on outdoor activities. Occasionnally on the winter, some task required to use radiation heater. This model has a glowing resistive wire for 230V supply (behind metal grill). For the reason that I am not fully aware today, I took a plastic handle metal file and started to poking the orange glowing wire throgh metal grill. BZZZAP !!! some sparks were seen and the heater did not work anymoreLuckily the metal file had a plastic handle, I assume it shorted mains live to earth ground (on the metal cover of heater)

author: SingedFingers
author_rank: Frequent Contributor
timestamp: March 14, 2017, 05:27:56 pm
content: We used to do that at school with the convection heaters. We'd even steal screwdrivers from the metalwork lab to jam in them.Until the main distribution board blew out the entire school. Turned out some dodgy wiring upstream meant serious consequences for this action (two weeks' detention)

author: Mrdouble
author_rank: Newbie
timestamp: December 29, 2018, 03:55:16 am
content: Hope I don't get in trouble for digging up such an old thread, my story is just too funny not to share 😁I guess I was 10 years old and I just got done helping my dad install my mom's new clothes dryer in the basement. Dad must have left for work At some point, I start playing with my slot cars and decided to disassemble it and hook the motor up to a nine volt battery. Pretty cool, if it goes this fast with a 9v, imagine how fast with 120V. I go downstairs and unplug mom new dryer and stick the wires in the outlet.Sure as anything... It spun up ungodly fast for a split second and then it exploded in my hands releasing smoke and making a big ol kaboom. I heard my mom upstairs running to see what happened and she flew down the stairs but I was faster than she was and removed all evidence and went outside. I walked in like I had no idea what happened. She informed me that she heard an explosion and now she can smell burnt electronics near the brand new dryer. I AGREED with my mom in that the brand new dryer must have just died. She was heart broken. I told her, let me take a look at it, maybe I can see something. Huh, the thing works fine. Thats weird lmao. I have since told my mom this and she called me "such a little asshole".

author: spec
author_rank: Frequent Contributor
timestamp: December 29, 2018, 05:35:06 am
content: This wan't my booboo, but Ann's next door who lives by herself.I had just come out of the shower when there was a loud and rapid knocking at the door. I chucked on a shirt and trousers and stood steaming at the door. "Can you come quickly, all the power in my house has gone and i can't even boil the kettle for a cup of tea for breakfast" "And the microwave is not working and I can't really afford a new one" I said I would be at her house in about ten minutes, and not to worry.Anyway, when I got to her house, I found that none of the sockets in any of the rooms had any power. This seemed rather strange, and it did not help that Ann kept telling me that she had already tested the sockets and there was no power there and there was no point in checking the sockets again. She said, "Can you fix the microwave?".Accompanied by further fault finding advise, Ann said that she had put the toaster and kettle on for breakfast but nothing happened. I went to open the fuse box, but was told that there was nothing wrong with the fuse box- it was the sockets that were not working. Finally I got the fuse box open and all four ring mains had tripped. This seemed strange, so I once again asked Ann what had happened and she said that she just turned the kettle and toaster on but nothing happened.After a load of negotiations I unplugged all items from the wall sockets in all rooms and gingerly rest the four trips one at a time: no problems. I then reconnected all appliances in all rooms apart from the kitchen: they all worked fine.Ann once more became anxious about the microwave, so I plugged it in and turned it to minimum. Ann immediately turned the dial up, saying that you would not be able to cook anything on such a low setting. I turned the dial down. She turned the dial up. In the end I asked her to stand back. I turned the dial back down, switched the microwave on and, low and behold, it lit up as normal and subsequently heated as normal. Ann was overjoyed and asked how I had fixed the microwave. From then on she seemed to have some confidence in my skills as an electrician and let me get on with the investigation without further advice.I next tried the cooker and that was fine, so the only thing left was the kettle and there was the fault. The entire area under the handle, where the cable plugged in, was like carbon. I asked Ann how old the kettle was. She said that she bought it just after uncle Arthur died. I told her that she needed a new kettle. She was overjoyed yet again and said that just the other day she had seen a nice kettle in town that she liked. So all was well, but I could not understand why the trips had thrown for the other rooms. Then, after a bit of coaxing, I found out. When the kettle and toaster didn't work in the kitchen she thought she would still be able to have a nice cup of tea by plugging the kettle into the sockets in the other rooms... but none of them were working either.

author: spec
author_rank: Frequent Contributor
timestamp: December 29, 2018, 05:56:28 am
content: Quote from: blueskull on December 29, 2018, 05:43:46 amThe kettle was not a dead short and with modern trips you often do not get a bang with an overload. Also, ground current could have blown the trips.Logic and old ladies do not necessarily go together, especially ones that live on there own, are very independent, and know a bit about, painting, gardening and... home electrics.On another occasion, with the same lady, she asked me to have a look at her TV which kept switching off during her favorite program. When i got there I had to smile. She had an ancient extender block, plugged into another ancient extender block and everything was plugged into these two extender blocks which were running pretty hot.

author: spec
author_rank: Frequent Contributor
timestamp: December 29, 2018, 06:28:26 am
content: Quote from: blueskull on December 29, 2018, 05:43:46 amMe too. Around eight years old I came pretty close when messing with an old fan motor. I had that jangling feeling and couldn't let go for a few seconds. Ever since then, like you, I have had a great respect for anything over 60V.We once had a cooker that would regularly blow rings so often that I always kept a couple of spares. One Sunday morning a ring blew and the missus was not too happy because it interfered with the Sunday roast sacred proceedings. No probs I said, I will have it fixed in 15 minutes.I turned off the switch on the wall, unscrewed the back panel of the cooker, which I had done many times before, and with my treasured electrical screwdriver which my Dad gave me, started to unscrew the ring wires from the terminal block. There was an almighty flash and the complete blade of the screw driver vaporized... instead of turning the cooker switch off, I had turned the kettle switch off.

author: InductorbackEMF
author_rank: Regular Contributor
timestamp: December 29, 2018, 06:43:21 am
content: I have a "Fun" story. Found a great ebay deal of a hp counter with all options, it was a rather old unit of about 20 years,so as usual i thought "Oh i better check the capacitors" after removing the two mains caps first and testing them (they were 100% ok) i thought "lets turn it on to make sure i did not screw anything up..With out putting them back.. well it sure as F@ck turned on in a great flash ALL capacitors went bang sending stuff flying and blowing the power supply fuse and killing half of the regulation what then put unregulated 25v on the 5v logic boards...Long story short fixed the power supply all capacitors changed and need a new connector.Alex.

author: ivaylo
author_rank: Frequent Contributor
timestamp: December 29, 2018, 07:22:18 am
content: Yeah, this topic should be permanently open... A stupid thing I constantly do is put back together whatever I’m messing with, only to notice a little part which I forgot and to put it back in I have to disassemble everything again. Tryed a few systems of organizing stuff, they work, but once in a while something will slip

author: spec
author_rank: Frequent Contributor
timestamp: December 29, 2018, 10:31:20 pm
content: Quote from: InductorbackEMF on December 29, 2018, 06:43:21 amsorry, but that was so funny- just the sort of thing I would do.

author: ChristofferB
author_rank: Frequent Contributor
timestamp: December 30, 2018, 04:07:32 am
content: Once I was wire-wrapping up an 8-bit computer board I had designed, had all the ic sockets super-glued in place on the board, had my schematic and wiring list and went on with it, wanting to be done in one stretch. I didn't have any of those little wrap-id tags with the pin numbers but I thought I had it figured out. Turns out "most" ic's have their pinout mirrored when seen from belowI had wired maybe 2/3 of the board before noticing. I seriously considered bending all the dip chip pins back 180 degrees or botch-soldering them on from below. Project never got further.

author: bitbanger
author_rank: Regular Contributor
timestamp: December 30, 2018, 04:53:05 am
content: Most costly mistake: was bench testing/commissioning a brand new VFD and wired 480/3ph into the motor output terminals (input and output terminals were beside each other in this drive). Was fused at around 30A. Instantly destroyed. I was very lucky to have an understanding employer (and a job after that).

author: SeanB
author_rank: Super Contributor
timestamp: December 30, 2018, 05:15:18 am
content: Quote from: ChristofferB on December 30, 2018, 04:07:32 amI flipped them, redoing the board ( home etched using a Dalo pen and letraset) was going to take too long, plus Saturday afternoon and no more blank board left. Still working last time I saw it.@bitbanger, Ouch, I know the smoke that lets out, and yes in pretty much every VFD those terminals are next to each other. Worse is having one terminal of each swapped, the VFD almost survives.

author: Kasper
author_rank: Frequent Contributor
timestamp: December 30, 2018, 05:37:50 am
content: Years ago I held a can of conformal coat too close and sprayed through the masking tape that was covering 200 pin (4x50) headers on a bunch of boards. Spent over a week replacing headers. On the plus side, my solder wicking skills improved.

author: KaneTW
author_rank: Frequent Contributor
timestamp: December 30, 2018, 05:43:55 am
content: Same thing happened to me. Conformal coating just went straight through the masking tape. Fortunately I was working in multiple layers and it didn't cover too much, but could've been bad.

author: Kasper
author_rank: Frequent Contributor
timestamp: December 30, 2018, 06:23:51 am
content: You are lucky. Or perhaps smart, for using multiple layers.I was unlucky, the cc was bake on and thick.

author: basinstreetdesign
author_rank: Frequent Contributor
timestamp: December 30, 2018, 08:29:29 am
content: Most expensive mistake by me:Back in the day (1980) when I was the house engineer and production manager for a small co, I sent the photographic negatives of a pcb 2-sided artwork out to fabricate 20 boards (TH) for a short run of a new product we were introducing. After about two weeks they came back, were assembled and waited to be tested. The boards had a large edge connector on one edge. The boss decided he would try out the first ones and 20 minutes later I found him still scratching his head over them and not looking happy. Then he looked at me and informed me that they were "useless".I had failed to check the negatives to make sure that the Component and Solder sides were indicated on the photography. The layout guy didn't put any text on them to make sure that they could be correctly identified and the fab house just went forward with no warning to us and assigned the two layers at random. Of course, they got them backwards.That was a lot of money and time down the drain and I never made that mistake again.

author: BFX
author_rank: Frequent Contributor
timestamp: December 30, 2018, 02:15:57 pm
content: This is not my mistake but there was lot of funSome company was repairing electricity installation on reconstructed floor in our company and some clever guy connected second phase to ground line(obviously not properly grounded;D)In a moment of big flash around 20 computers shuts down with small flash and sizzle noise around 30 LCDs and 6 laser printers went to big flash and white magic smoke escaped from every one of themWhole floor was one big smoky space and horrible smell.

author: Howardlong
author_rank: Super Contributor
timestamp: December 30, 2018, 02:39:14 pm
content: Like some others, this one’s not my mistake (I make plenty of my own thanks), but about 12 years ago I was brought in at he last minute to deal with a problem with a satellite that was still in the clean room, but was due to be shipped off to the launch location in 48 hours. I jumped on a plane, and at the facilty donned my clean room paraphernalia and took a look.The problem was that the downlink transmitter went into self oscillation once hooked up to the antenna. In earlier testing, all went well, but dummy loads had been used in place of the antenna.The antenna had been modified from an earlier design, and with a VNA I saw that it presented an appreciable mismatch, a return loss of about 8dB. This mismatch made the HPA become unstable. The engineer behind the HPA wasn’t available, of course, but everythig had been conformally coated anyway.In the end I empirically measured how to tune out the mismatch by varying the length of the feeder. We had a new custom length feeder made (these kinds of places have in house RF cable fabricator experts with special tools made from unicorn foreskins) and that was what went into orbit.Of course, there’s quite a bit more behind this story, but the salient facts are as noted.More importantly, my hack worked.

author: vk6zgo
author_rank: Super Contributor
timestamp: December 30, 2018, 03:04:48 pm
content: Not my mistake, but my brother told me about this one which happened during a rocket launching done for the Brits at Woomera back in the early '60s.The rocket had two antennas sticking out of its side at right angles to the vertical when the thing was sitting on the launch pad.These supplied a signal which radio receivers at each end of the range would receive to give an idea of where the rocket was along its path.Another important function was, if they both lost enough signal level, it basically meant the thing was lost, so it would be blown up for safety.The system was, of course, set up with the antennas horizontally polarised on the pad.When the rocket lifted off, all went OK, until it tilted over to travel down range.Both receivers immediately suffered a 20dB loss of signal as the antennas were now vertically polarised.The system monitoring the receivers switched back & forth between them rapidly a few times, then basically, "threw its hands up in despair".The Range safety officer pressed the big red button.------ A few million Sterling down the drain!The EEs fixed the problem for the next test by the simple expedient of going up with a rubber mallet & tapping the antennas so they were sloping at 45 degrees to their original orientation.A bit less signal all the time, but it didn't change significantly with vehicle orientation.

author: IDEngineer
author_rank: Super Contributor
timestamp: December 30, 2018, 06:00:34 pm
content: OK, my story doesn't match "intentionally destroyed a spacecraft due to antenna polarization" but it does echo what some others have written.I was in the brand new electronics lab in high school, working on an oscilloscope with a buddy. We were both sitting on four-legged stools at the workbench. The scope's power was off and unplugged, but there was still a nice charge on the CRT's anode terminal which I somehow touched while also in contact with the chassis by my other hand.One moment, I was sitting on the stool. The next moment I was on the floor, across the room, with my brain wondering 1) where my buddy had found the hidden baseball bat and 2) why he had hit me in the chest with it. That was the only sufficiently violent explanation my brain could come up with right away for how much my chest hurt and how I'd gotten across the room without remembering the trip.I rank this as a mistake because I clearly needed to better learn the "one hand" rule.On a related note, and at about the same age, I was working on my parent's car which was backed into the driveway. I believe I was changing the fuel filter. Naturally this process spills a bit of gasoline, but in this case it spewed quite a bit of gasoline and the fuel line was still spraying it around a bit... when the screwdriver I had been using rattled off wherever I'd carefully set it and fell, very precisely, onto something associated with the starter. Might have been the starter terminals themselves, might have been the solenoid, all I know for sure was it wasn't the battery because I was careful to NOT put tools anywhere near the battery for obvious reasons. However, Darwin felt I needed further instruction that day and so directed the screwdriver toward a nice source of arc-welding-capable current just the same!In this case, my autonomic nervous system took over. In what must have been a record-setting backwards standing broad jump, I somehow levitated from the front of the car to the middle of the street in a single motion. Had to be 20 feet. I remember the whole trip, while watching the car for the fireball I knew would result from an absolute shower of sparks being happily sprayed by fresh gasoline. But Darwin apparently had had sufficient fun with me, so after a few more seconds the tool rattled to the concrete below the car. There was no fireball, no damage to the car, and the tool (I think it was a screwdriver) only had the characteristic burn marks from such shade-tree welding mistakes.I rank this as a mistake because I clearly needed reinforcement on the "disconnect the battery" rule.Ah, youth....

author: madao
author_rank: Frequent Contributor
timestamp: December 30, 2018, 08:11:27 pm
content: This schematic show output stage of Tek 114, the pulsgenerator.This unit can provided negative and postitive output.I think at frist: Woho, bad drawing, there is short, if i switched it to negative puls.But it isn't, because puls-generator is floating and has own circuit ground.

author: Karlo_Moharic
author_rank: Regular Contributor
timestamp: December 30, 2018, 09:27:02 pm
content: On one occasion I set my multimeter on fire. On different occasion I've imploded a large CRT to pieces.

author: TheNewLab
author_rank: Frequent Contributor
timestamp: December 30, 2018, 09:45:00 pm
content: wondering why all my voltage readings were OL, so stuck the probes into an electrical outlet to check the voltage reading..the probes were attached to...you know what Light, action! and poof.smoked the meter. Maybe I was lucky. I could only laugh that I did not kill myself

author: vk6zgo
author_rank: Super Contributor
timestamp: December 30, 2018, 11:42:07 pm
content: Quote from: IDEngineer on December 30, 2018, 06:00:34 pmIt just shows that movies & TV lie, & it is a lot harder to blow up a car than they would have us believe.About youth...Back in the "dear, dead days beyond recall", my first car was a 1936 Chev Standard sedan, with an Australian made Holden body.The torque tube rear axle was faulty, so, after much searching, I found a used one (the "Master & Standard models were different).The easiest way to remove the rear axle seemed to be to disconnect the brake lines, undo the "U bolts" holding it in place on the semi-elliptical springs, & pull it out from the rear.As it was an old, very high set vehicle, I assumed that the springs saton topof the axle, so proceeded to undo the U bolts, thinking the body would still sit there, till I dragged the rear axle out.My assumption was incorrect, so the bloody thing fell on me, one of the released springs giving me an almighty bash on the chest.I am not dead, thanks to the idiosyncratic body design, where the rear mudguards ( fenders US, wings UK), tapered very sharply into the body at their top.The tyres on the 17" whels wedged in this tapered part, preventing the Chev body from falling completely.( thank you, Mr Holden!)I dragged myself from under the beast, & decided I would go & ask Mum for a cup of tea, after which, I would go & have a good long "lie down".

author: jmelson
author_rank: Super Contributor
timestamp: January 02, 2019, 03:10:41 am
content: Quote from: IDEngineer on December 30, 2018, 06:00:34 pmWell, there's a totally fantastic story about a satellite dropped on the floor! In 2003, the NOAA-N satellite was in the clean room at Lockheed, and being tested and checked before launch. They had two "turn and tilt" facilities, devices that could tilt the satellite over so you could get to any part of it without climbing. But, they only had ONE SET OF BOLTS to secure the satellite to the facility. Somebody moved the bolts over, worked on one satellite, then put the bolts back in the other one but did not tighten them! Perfect setup for a mishap.See :https://space.stackexchange.com/questions/1783/was-the-noaa-n-prime-satellite-really-dropped-on-the-floorfor info and pictures, this stuff is TOO good to be true! I use it as one of my desktop backgrounds.Jon

author: Rerouter
author_rank: Super Contributor
timestamp: January 02, 2019, 03:23:40 am
content: I assume with the subtitle "Just order more bolts next time"? :p

author: NikkiC
author_rank: Contributor
timestamp: January 14, 2019, 03:48:16 pm
content: I had acquired an old Yaesu FT-101 transceiver from a junk pile and decided to restore it. Every last plastic capacitor on every board had shattered it's hard outer shell with only the inside foils showing. The PCB's and the connectors they plugged into had serious corrosion problems, and mold was growing on pretty much every thing in the upper and lower chassis. It was a nightmare from hell working on it because I had never attempted to repair / restore a transceiver before and I literally had to almost disassemble the whole thing to address the mold and corrosion issues.I cannot over emphasize the difficult challenges this project would present to even a seasoned veteran. It was an infinitely deep rabbit hole to be dropping into. The ganged band switch repair deserved it's own little corner in hell because the rest of the transceiver is literally built around it. The control pots on the front panel had little bugs crawling out of them. The VFO was particularly problematic due to the mold. The regulator board was completely shot to the point where 13.5v was being applied to all the circuitry! There were problems in selecting proper transistor substitution in RF circuits, throwing impedance off. I had to learn how to make intelligent choices in transistor substitution, sometimes necessitating changing biasing resistors to accommodate. Each and every PCB had to be repaired in some fashion or another. The regulator board, I completely stripped of all parts and completely rebuilt it from scratch with all new components. Ditto that for the audio board. No, I wasn't going to go on Ebay to find replacement boards. At the end of my odyssey, I had a pile of parts from the other boards that were repaired:5 IC's15 transistors45 capacitors22 trimmer capacitors20 resistors11 diodesAll said and done, it took me over 2 years of burning the midnight oil to get the rig functional. The receiver's performance I was particularly proud of, it was a joy to operate and listen to. There was only one last thing I needed to do before bolting on the covers: Replace the panel lighting with LEDs. Not a big deal after all I had done to the rig the previous 2 years right? I couldn't decide on what color LED's I wanted to use. So I had to try different variations of white, red, pink, purple blue, orange, yellow or green to see which one I preferred. In the end, I used RGB LEDs attached to a little circuit with a switch allowing me to switch between different colors. This little PCB was powered by the raw unregulated 13.5v power delivered from the rectifier board to the front panel bulbs. Somehow, I managed to short out this voltage to ground. The result was not pretty. It burned the power wire in the main wiring harness coming from the rectifier board to the front panel bulbs. When this wire started burning, it set parts of the entire harness ablaze, destroying the adjacent wiring. Somehow this caused a system wide failure in the receiver. Even after repairing the wire harness (another trip across the river Styx into hell), the receiver was dead. No LO. No RF gain. Even the mixer was dead.It never did pop a fuse, instead it fried the 13.5v rectifiers. After all the pain and misery I had gone through with this radio and to have this happen was beyond belief.I'm such an idiot and should never be allowed to touch a piece of electronic equipment ever again. I cried. I really cried. That was a few years ago and I'm still. I literally gave up on electronics for a while. It really destroyed all the confidence I had in myself. Humiliating. Almost like doing arm -rf /as root. Mortifying! So after a year, I realized I love electronics to much to just give it up. I made a mistake. A stupid one but I learned a few things from it and will likely make yet more mistakes before it's all over. But still.... I'm an idiot. Really really.

author: rsjsouza
author_rank: Super Contributor
timestamp: January 14, 2019, 04:22:17 pm
content: Wow... Thanks for sharing your story. That was really painful and reminded me of a terrible goof up.A friend lent me his father's old Ford ignition coil so I could remove all the grime and rust over the years - the last time it was used was a couple of decades ago a Jacobs ladder to entertain his sons. I went ahead and tested all the impedances and even put it for a spin on my bench power supply - 6V @ 1 or 2A. I then proceeded to clean all the parts and left it bright and shiny! A beautiful piece nonetheless - I even did some research and, based on the information I got, it was manufactured at the late 1920s for the Ford A models.Well, minutes before I left for my friend's house to return it, I decided to put it to run one last time just to see if everything was A-OK. I set the power supply to 6V and, when I connected to it, there was no life - the power supply was brought to about 2V. I then correctly realized the output current was probably set too small and increased thevoltagepotentiometer. I realized my mistake and the proceeded to increase thecurrentpotentiometer, but forgot to bring back the voltage one. Result: a blown coil due to ~14V applied to it.My friend did not mind too much, but after all it was a family heirloom. Unfortunately I could never get around to fix it since my daughters were born not long after this event happened, and the energy was completely relocated to this new "project". That still haunts me, especially because it was a friend's treasured possession.

author: IDEngineer
author_rank: Super Contributor
timestamp: January 14, 2019, 05:19:51 pm
content: Quote from: NikkiC on January 14, 2019, 03:48:16 pmThis is the winner (loser?) for me with respect to "smallness of mistake to magnitude of damage". Wow, do I respect rebuilding that FT-101 given the condition you describe. And then to have it wiped out like that... very tough. Glad you came back to electronics, though. As painful as that had to be, it doesn't mean you have to give up an entire career/hobby.

author: schmitt trigger
author_rank: Super Contributor
timestamp: January 14, 2019, 05:24:01 pm
content: Quote from: Benta on January 10, 2017, 10:06:44 pmExactly the same happened to me.I kept a few. Only now do I realize that they are VERY few.

author: KL27x
author_rank: Super Contributor
timestamp: January 15, 2019, 02:57:14 am
content: ^https://www.eevblog.com/forum/beginners/printing-out-huge-datasheets/msg1260733/#msg1260733In short: you can have single copy of a book printed from PDF for something like 15 or 20 bucks.

author: martin1454
author_rank: Regular Contributor
timestamp: January 15, 2019, 12:28:06 pm
content: One of my close calls were a few years ago.I was into Airsoft, and just had gotten a new airsoft gun. The new gun used Deans connectors for battery, and my current battery had tamiya plugs, but I had a few loose deans connectors in my spare box.I grabbed my side cutter and cutbothof the wires at the same time. It was a 3S Lipo battery, and it infated greatly, so I quickly grabbed an bowl and placed it outside - Luckly it never burst into flames - My guess was I was lucky that the coating of the side cutters gave it enough resistance not to blow up

author: malagas_on_fire
author_rank: Frequent Contributor
timestamp: January 15, 2019, 12:44:40 pm
content: this ... Bad measuring technique on NINH with load ....https://www.eevblog.com/forum/testgear/hear-kitty-kitty-kitty-nope-not-that-kind-of-cat/msg2102542/#msg2102542

author: AE7OO
author_rank: Regular Contributor
timestamp: February 27, 2020, 02:39:28 pm
content: Digging deep to necro an old topic...When I was still in the Navy I had a power supply go out for one of the sat comms.So I kill the power, tag it and then proceed to drain the caps. I had just got done doing the first round, when I was called away to help another ET. I came back to it about an hour later.I'm not sure what was going through my mind(or not as the case maybe), but I proceeded to start troubleshooting it. When working these things I kept one hand in the pocket, just in case(3000V is high voltage after all...)Some how when I was metering some part, I managed to touch one of the cap bolts with my left forefinger and my elbow with the case. At this point I get woken up by having my entire left forearm feel like it's been smashed. After about 10 seconds it starts to fee like hot oil was poured on it and I let out a scream. After a trip to the hospital I come to find out that I had burned various parts of my arm, and to this day I have a sensitive pock mark almost dead center of my left forefinger.Normally I would have drained those caps a minimum of 2 times if not 3 about 5 min apart. I could not recall why I did not this time, and never came up with a good reason why I failed to do so.I'm lucky that the highest voltage I'm around now is 13.8 VDC because my memory is going...

author: Leonhard Bandilla
author_rank: Contributor
timestamp: February 27, 2020, 02:56:42 pm
content: Yeah, I once shorted a 100A power supply, dead short. The supply didn't even go into overcurrent but cleanly evaporated the PCB traces off the board. I though in that case I would hear or smell sth, but I only noticed it when I inspected the board. Around 1mm of trace was just evaporized on all off the VCC and GND traces in the area of the short

author: schmitt trigger
author_rank: Super Contributor
timestamp: February 27, 2020, 05:33:50 pm
content: @ AE700:You learned the hard way about capacitor dielectric absorption.It has happened to me also, but fortunately at FAR lower voltages, about 400V from a vacuum tube power amp.

author: Larryc001
author_rank: Regular Contributor
timestamp: April 18, 2020, 02:41:32 am
content: i love these things! I unfortunately can’t tell you about my biggest mistake. Let’s just say it involved my wife and my best friend. But I did witness a cock up when I worked at a radio observatory. We had installed a large no-break generator capable of running everything. It had a huge flywheel which kept the generator turning while the diesel started and took the load. It used a bank of huge 24 volt lead acid batteries wired in parallel to start the diesel. This day our mechanic was working on the unit and dropped a large crescent wrench onto the battery bank. Of course it shorted the batteries and was instantly vaporized. He said he was lucky it didn’t just short the batteries as they might have exploded before he could escape. Close enough for both of us.

author: moffy
author_rank: Super Contributor
timestamp: April 18, 2020, 04:32:16 am
content: Nearly falling out the open door of an aircraft after being electrocuted.I was working for Ferranti, a defence contractor, on their ring laser gyroscopes. The lasers have a -1500v cathode which is ignited with -10kv pulses until the laser strikes. It was fitted (the laser gyro) near the open door of a Ferranti owned jet while on the tarmac. There was a prism that needed adjustment to align the the in and out beams so that you had a mixed signal. The resulting FM beat signal told you how many arc degrees you had rotated. So in this awkward position I was trying to align the prism with my right hand and didn't pay any attention to where my left hand went as it solidly brushed the cathode. Bam, -1500v then these 10kv spikes! Managed to not fall out the open door but was somewhat unsteady for a while.The flight went well however and the gyro performed well.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 18, 2020, 08:05:11 pm
content: stupidiest mistake, was to cut at my job an ac line cable to repair a connector, forgotten it was alive, a beautiful big bam, i was lucky not having i direct eyesight, cutted to power to many test benches ... oh the cutter did not survive

author: IDEngineer
author_rank: Super Contributor
timestamp: April 20, 2020, 05:26:37 pm
content: Quote from: coromonadalix on April 18, 2020, 08:05:11 pmI watched a remodel subcontractor do that. He didn't ask if the romex was live... nor if the breaker had been turned off... not even where the breaker box WAS. He just got out his linesman's pliers, clamped around the romex, looked away, and squeezed. He got lucky and nothing happened.I asked him about it and his response was "We always do it this way."

author: David Hess
author_rank: Super Contributor
timestamp: April 20, 2020, 08:08:38 pm
content: Quote from: IDEngineer on April 20, 2020, 05:26:37 pmI have done that on live circuits before. It is the fastest way to find which breaker it is but it can be hard on the diagonal cutters.

author: engrguy42
author_rank: Frequent Contributor
timestamp: April 20, 2020, 08:08:55 pm
content: Regrets, I've had a fewBut then again, too few to mentionI did what I had to doAnd saw it through without exemptionI planned each charted courseEach careful step along the bywayAnd more, much more than this, I did it my wayYes, there were times, I'm sure you knewWhen I bit off more than I could chewBut through it all, when there was doubtI ate it up and spit it outI faced it all and I stood tall and did it my wayOh, and the other day I forgot to checka resistor wattage. Big resistor, I figuredno problem.Turns out it was only 2 watts.Lots o' smoke....

author: temperance
author_rank: Super Contributor
timestamp: April 20, 2020, 08:25:22 pm
content: My most stupid mistake?Getting into electronics must have been my biggest mistake. There are less demanding jobs with a better looking pay check at the end of the month for doing nearly nothing.I've met managers in my career who can't even write a proper e-mail...

author: david77
author_rank: Frequent Contributor
timestamp: April 20, 2020, 08:42:34 pm
content: The ideal thread for me right now. I've just left the lab and I'm pretty pissed off.First I've accidently smoked my AVRISPII by leaving it plugged in to a circuit under test and then being stupid enough to put 100V DC onto that board. The board was fine, that project is meant to be connected to up to 100V DC. But somehow I managed to kill the AVRISP.Oh well, stupid me. Should have pulled the plug.Ripped the programmer open to find a cooked voltage regulator. Maybe that is all that died. Ordered it online. We'll see.Then I had the brilliant idea to use the Minipro TL866A as an ICP. Ha! I can continue! Made up a suitable lead to connect it to my project (they provide you with a schematic to do just that!). Checked it twice and plugged the TL866A onto my board.And then I had an Electroboom moment. The TL866 made a sweet POP sound and my nearly finished project let out a cloud of smoke.Now everything is toast.I've checked my lead again and it is fine, no miswire.Sometimes I hate my hobby...

author: Messtechniker
author_rank: Frequent Contributor
timestamp: April 20, 2020, 08:44:52 pm
content: Only recently.Did some troubleshooting on the power supply board of a NETIO 230A relay switch.As usual the secondary smoothing cap had it.Had to wait for the replacementto be delivered. Did a lot of 12 V work in the mean time. Then installed the cap and tested the board it with 12 V instead of 5 V.Thanks to the low current limit setting on my lab power supply it did not go Kaboom.To my surprise the current draw was a bit on the high side. After a while I realised what I had done wrongThe board (with a connected load resistor) then tested OK with the proper 5V supply voltage. This goes to show you the usefulness of current limiting lab power supplies. Using an ATX power supply would certainly have killed the PSU board for which a replacement is hard to find because of size restrictions.

author: coromonadalix
author_rank: Super Contributor
timestamp: April 21, 2020, 02:22:59 am
content: Gonna add another loll In my "twenties"Discharging a tv image tube, the screw driver was supposed to be grounded with a wire, my hand was moist and i was touching my steel bench in some waysGuess the way the discharge took .... my hand a 35kv discharge and a very defined small hole in my hand, boy my heart was beating like crazy

author: hwj-d
author_rank: Frequent Contributor
timestamp: April 21, 2020, 12:59:15 pm
content: If I was a very young boy plenty, PLENTY years ago, I want to measure ac-current directly at power socket with my brand new dmm...

author: thinkfat
author_rank: Unknown
timestamp: April 21, 2020, 03:07:29 pm
content: Quote from: hwj-d on April 21, 2020, 12:59:15 pmOooh, yes! Yes! I tried the same, not with a DMM though, but with a Hung Chang analog multimeter. Quite the bang!

author: IDEngineer
author_rank: Super Contributor
timestamp: April 22, 2020, 07:06:03 am
content: I did the multimeter AC socket thing too, at about 6YO. Took it back to Radio Shack and the manager knew INSTANTLY what I'd done. He smiled and handed me a replacement. Not his first rodeo, I'd wager!

author: Electro Detective
author_rank: Super Contributor
timestamp: April 22, 2020, 09:55:53 am
content: The multimeter AC socket connections to measure current in a 240 AC voltage based socket thingis still alive and well in 2020and decades later the manufacturers and Chenglish scripters STILL do not make mention of the dangersSure, lots of 'how to',but no'how not to'The marketers need to be worded up that trashed meters and zapped prodders, does not promote sales or instigate repeat purchase of same brand product

author: Larryc001
author_rank: Regular Contributor
timestamp: April 23, 2020, 04:19:20 am
content: At least I didn’t do anything this bad:https://en.m.wikipedia.org/wiki/2009_Sayano-Shushenskaya_power_station_accident

author: thinkfat
author_rank: Unknown
timestamp: April 23, 2020, 01:28:30 pm
content: I believe my stupidest mistake was running some random shell script that supposedly converted PDF to Postscript as "root" user on my linux system. It eventually executed a "rm -rf /" and took out the whole system, including large parts of $HOME. I lost a lot of stuff, including source code of projects I was working onIt hit my like a brick when I realized what was going on.

author: senso
author_rank: Frequent Contributor
timestamp: April 23, 2020, 01:56:39 pm
content: Stop and photorec all the files?

author: thinkfat
author_rank: Unknown
timestamp: April 23, 2020, 02:02:56 pm
content: Quote from: senso on April 23, 2020, 01:56:39 pmThat happened long before photorec existed.

author: david77
author_rank: Frequent Contributor
timestamp: April 24, 2020, 04:18:02 pm
content: Haha. Yeah I did something similar when I was a total Linux noob (I'm still not a power user).Was logged in as root and had the brilliant idea to enterchown -R user:group *while I was in my root directory. Had to start over with that box, I still wouldn't know how to recover from that tbh.

author: IDEngineer
author_rank: Super Contributor
timestamp: April 24, 2020, 08:37:39 pm
content: That reminds me of an event. Not exactly a mistake, but....Back in the mid-90's when Linux was just catching on, I got one of the early versions of Slackware so I could start getting familiar with the environment. I set up a dedicated machine, monitor, keyboard, mouse, etc. for it. Spent hours getting it loaded and running. Then, as I tilted back in my chair after a multihour session, I bumped the table and one end of a cable fell off the back of the table. The gap to the wall was just wide enough to allow it through, and it swung down and hit......the switch on the power strip.Naturally, this depowered the file system without proper shutdown. The machine simply would not boot anymore.If nothing else made believe in Murphy's Law, that did it. This was an eight foot long table. The "OFF" side of that switch was what, maybe half an inch wide? 94% of the linear distance was completely harmless. Yet somehow it fell in theone exact spotthat could cause not only inconvenience, but a lot of it. Countless hours wasted. Oh well, the second time (re)building the machine went a lot faster!I had UPS's around, so I immediately went looking for a UPS solution. And there weren't any. Nobody had a daemon that could run, like a Windows Service, to detect power failure from the UPS and prepare the file system for shutdown. I called APC and someone else big at the time (maybe Tripplite?) and the universal response was that it was impossible to write such a daemon. They'd tried and tried, hired various software people, and every one said it couldn't be done. As I recall, the reason was some chicken-egg situation where a daemon could not continue to operate without access to the file system - the act of dismounting the file system caused the system to lock up just as if the power had been cut anyway.Hmmm....So I wrote my own daemon. My trick was stabilizing the system by shutting down most processes, thenremounting the file system in Read-Only mode. Worked perfectly. RO allowed the operating system to continue functioning, and the daemon didn't try to write anything so it didn't care. If power came back the daemon simply remounted the file system with RW access again. Otherwise, it stayed in RO mode and you could cut power at any time. I tested that dozens and dozens of times, never failed once.I had fun calling the UPS companies and telling them I'd solved their problem. Most of the people refused to believe it, and most of the rest didn't know enough to understand what I was talking about. However, I noticed that a few years later magically they DID have Linux daemons available. Presumably someone else thought of it too, or Torvalds changed something.The original incident did teach me an important lesson which I practice to this day: Unless I'm using it to control everything on the strip (like on my soldering bench), I put duct tape over the power switches on power strips.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 13, 2020, 02:03:24 pm
content: Currently feeling very stupid for having discovered that you can fit a USB C plug (inadvertently) into a USB A socket very nicely.I might have been more careful had the PC been on as I tried to plug said USB C into the single back panel port reaching into limited space and mostly trying to get it into the right spot by feel, but it was powered down so I wasn't too worried.However I forgot that the board supports wake on USB so the port will have been powered. I have probably killed the +5Vsb supply - time will tell whether this will need a new PSU, new M/B or if I will just get away with replacing an SMD fuse somewhere but it's an ITX board in a tight SFF case so I don't think I'm even going to be able to get a multimeter probe in the ATX connector without stripping the whole thing down.Rats, there goes the afternoon.EDIT:M/B confirmed as dead - the PSU boots a spare ITX M/B just fine - not surprising as it is a half decent Seasonic and probably overcurrent protected to the hilt.On the bench the damaged M/B is half alive - it sort-of tries to post & boot but does not make it into the BIOS. Next Q is whether I just replace the motherboard or use it as an excuse to go to a Z490 board and a 10thgen CPU (or AMD, but that might be a step too far).Disappointingly easy to destroy the board though.

author: phil from seattle
author_rank: Super Contributor
timestamp: June 13, 2020, 04:35:17 pm
content: Yeah, just added a new one to my wall of shame. Custom circuit board that allows configuration of 5V or 12V for relay drivers. I originally designed with a 1x3 pin header - short 1-2 for 5V, 2-3 for 12V. Next rev, in my brilliance, I added a 2-way solder-jumper to do the same thing but left the pin header. At some point I decided to test out 12V support with the solder jumper and, as I'm sure you figured out by now, forgot that I'd been testing 5V support earlier. The multiple plumes of smoke rising from the board was my first indication that something was wrong. 12V Blew out my only teensy 4.1 and every chip on the base board. $35 worth of stuff gone wasn't a big loss but I was stuck for 5 days before getting back to the point where I could continue testing.

author: jeffheath
author_rank: Regular Contributor
timestamp: June 15, 2020, 12:02:58 am
content: -The first time I set a car on fire-I was trying to get an old ford with a 352 started again, can't remember why it was taking me so long, it probably had a bad condenser. Anyways, there was leak at the fuel line going into the carb, and the intake was covered in fuel. I just remember that as soon as I turned the key, BOOM! There was giant ball of fire in the engine bay! I tried to beat at it with a towel, this only made it worse, and caught the towel on fire. I then ran to get the water hose, which was of course too short, and then eventually put it out after god knows how many buckets of water. I had to get a new carburetor float, spark plug wires, and other things, as they were melted. I think a spark from the solenoid probably shot over to the fuel when I went to start it.-The second time-This one's even more stupid. I had just finished welding the floors up on a 40's chev I have, and had already put the seat back in. These cars are notoriously hard shifting when converted from vacuum shift, so I wanted to lengthen that shifter arm to give it more throw, by welding a piece on. Of course it's a column shift, which means that the shifter is behind the steering wheel,above the seat.The seat, which was covered in 70 year old upholstery, but I was too lazy to take back out... anyways, as I was welding, I was wondering why my arm was so hot... it wasn't like normal weld spatter, and that's because it wasn't. I lifted my mask, and sure enough, the entire front of the cab was filled with flames. Even more frantic running around with hoses and buckets followed.

author: m3vuv
author_rank: Super Contributor
timestamp: June 15, 2020, 07:47:35 am
content: I was doing a repair on my old kenwood tr-9000 transceiver ,the idiot protection diode was leaky and getting hot,instead of replacing it i removed it,the power connector wasnt the propper one for the radio,guess what happened next?,i put it in backwards,so reverse polarity for the radio,it killed the led driver ic,this was no longer made so scrapped a good radio,talk about having a blonde moment! lol,live and learn.

author: m3vuv
author_rank: Super Contributor
timestamp: June 15, 2020, 10:37:52 am
content: think one of my wost mistakes was agreeing on her ass looking big/fat in a new pair of jeans she had,she stabbed me,i nearly died thru blood loss,actualy collapsed at the a+e dept at the hospita!.

author: grumpydoc
author_rank: Super Contributor
timestamp: June 15, 2020, 11:37:30 am
content: Ouch I hope that you are pulling our legs because that seems something of an extreme reaction.Mind you my wife is quite capable of telling me I have no style, dress sense or understanding of colour co-ordination (all true) and then, 5 seconds later, insisting on getting my opinion on some item of clothing.

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 15, 2020, 11:39:17 am
content: Please tell me that's not true, m3vuv!One time I was talking to some people about the May Day festivities here. A couple of women were going to the main event at the center of the capitol city, and I happened to ask "How the hell are you going to fit in there?"Everyone there fell silent, and I could feel the eye-daggers drilling through to my soul. I am, and was then, a pasty white male. And the ladies were on the larger side. Uh-oh.I stammered, "Last time I was there the throng was so dense I couldn't breathe, and was close to panicking. And had to try to keep an eye at the sky too because kids were throwing glass bottles around too."That time, I got away without being stabbed. I guess they saw from my firetruck-red face that I didn't mean itthatway.

author: BradC
author_rank: Super Contributor
timestamp: June 15, 2020, 07:21:31 pm
content: Quote from: m3vuv on June 15, 2020, 10:37:52 amA mate of mine responded to “honey, do these jeans make me look fat” with “no, it’s the size of your bum that makes you look fat”. He slept on the couch for a week. Sounds like your (potentially ex) suffers from poor impulse control.

author: wizard69
author_rank: Super Contributor
timestamp: June 15, 2020, 07:34:27 pm
content: wow, I thought I was the only one to have gone this route.Quote from: gnavigator1007 on January 10, 2017, 05:26:44 pm

author: Zoli
author_rank: Frequent Contributor
timestamp: June 16, 2020, 05:09:22 am
content: Quote from: BradC on June 15, 2020, 07:21:31 pmStandard answer(and always works):"Honey, the best you look without them"

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 06:14:07 pm
content: Grabbing a 150 watt soldering iron by the heating element side. I thought it was unplugged.Getting shocked by 500 volts DC. Forgot the fact that bleeder resister was removed.

author: IDEngineer
author_rank: Super Contributor
timestamp: June 17, 2020, 08:35:05 pm
content: Quote from: tkamiya on June 17, 2020, 06:14:07 pmWhen I was a kid, I instinctively caught something that was falling off my bench. Turned out to be the soldering iron. And of course I grabbed the hot end.I quickly revised my thought processes to first analyze what is falling before automatically grabbing for it. You definitely have plenty of time to decide before it hits the floor - and sometimes LETTING IT HIT THE FLOOR is by far the best option!

author: Vovk_Z
author_rank: Super Contributor
timestamp: June 17, 2020, 08:40:34 pm
content: I was shocked by 450VDC through two fingers on one hand (one finger in - second finger out). My left hand was not ok about a three years. Since that time I'm afraid voltages higher then 25 VDC.

author: thinkfat
author_rank: Unknown
timestamp: June 17, 2020, 08:55:43 pm
content: Quote from: IDEngineer on June 17, 2020, 08:35:05 pmI made it a habit to watch the thing falling down closely to see where it goes. As most of the time it's the last mounting screw in the box, or a small, expensive chip...

author: ejeffrey
author_rank: Super Contributor
timestamp: June 17, 2020, 09:17:00 pm
content: Quote from: IDEngineer on April 20, 2020, 05:26:37 pmIt's the logical conclusion of "treat every circuit as if it is live"

author: Syntax Error
author_rank: Frequent Contributor
timestamp: June 17, 2020, 10:14:43 pm
content: Soldering iron burns are a right of passage for any aspiring EE. Wear your scars with pride!So what was my grand fau par? When I was a student I 'fixed' a failed Walkman power supply - well not a Sony Walkman, rather some made in Macau tape mangler in red plastic. Anyway... I opened up the power brick, tested for a voltage and, without looking/thinking, bridged the live and neutral points on the transformer with a metal screwdriver. So what happened next?A. A big flash followed by flashing blue lights?B. A flash and the lights went out?C. No flash, the screwdriver became the line fuse and then melted?D. I burnt down my student digs?For me, I was lucky. Answer B.So I threw back the curtain to let in the street light. And the street was dark. And the houses over the road were dark. In fact, much of London was in darkness. On the radio the power failure was due to a "power surge". A freakish coincidence?I only use insulated screwdrivers... just in case.

author: tkamiya
author_rank: Super Contributor
timestamp: June 17, 2020, 10:34:48 pm
content: Quote from: thinkfat on June 17, 2020, 08:55:43 pmIt's about 40 years too late to tell me that!

author: Nominal Animal
author_rank: Super Contributor
timestamp: June 18, 2020, 12:23:08 am
content: I got a nice burn scar across the knuckles of my left hand. I was baking rolls, and when pulling them out of the oven, one dropped.With my lightning reflexes () I grabbed it in midair, and immediately lifted my hand into the red-hot heating element inside the oven.You never really forget the smell.I openly admit I'm not one for effective multitasking. Icanwalk and chew gum at the same time, but that's about it.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 18, 2020, 12:29:50 am
content: Not something I did, personally, but a good story, nevertheless.Back in the day, all the telephone cables used by Telecom Australia were sheathed in a distinctive yellowish beige.On one occasion, the cable makers ran out of that colour, asked for & got permission to use the same grey stuff then used to sheath flexible Mains power leads for appliances.After that batch, they got supplies of the normal colour, & everything reverted to normal.Power extensions commonly used that same shade of grey, & thereon hangs a tale:-Exchanges had gone away from hanging dedicated cable ducts from the ceiling, & were using what was essentially a "false ceiling" made of perforated metal.The advantage of this was that cable runs could be made quickly & safely, compared to trying to add a bundle of cables to an already bulging cable duct.It became the habit to chuck power extension cables up there, too, as it kept them off the floor.After all, who'd mistake them for phone cables,---- the sheathing colours are quite different.OOPs!A Tech was working on removing a bundle of cables which were no longer used, all of which were grey sheathed.The easy way was to cut them & pull them back at both ends, so, grabbing the big sidecutters, he set to with a willA blinding flash, a remodelled set of cutter jaws, and alarms going off everywhere, revealed that one of those cables was a power extension!The Tech was OK, just somewhat chastened!An immediate order came out from headquarters that all power extension cords must haveredsheathing!.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 18, 2020, 02:28:49 pm
content: Quote from: vk6zgo on June 18, 2020, 12:29:50 amA good example of a mistake caused by a poor process!

author: Photoman
author_rank: Regular Contributor
timestamp: June 19, 2020, 02:55:42 am
content: Last week...I was changing the tip on my hakko desoldering gun.Took the sleeve off, put it on my helping hands, too tired and wasn’t paying attention when I reached over for the new tip.I smelt the burning flesh on my arm but it took a sec for the pain to register.A pretty nice 2nd degree burn. Almost healed now.Another really stupid mistake, put a fixed 12v LDO instead of a variable LDO that’s normally set to 3.3v.The part# was only 2 digits off. Only a few parts were fried, the input voltage was too low to fully turn it on.Only 5v got out before I realized my mistake. Oh well, loose some loose some!

author: vk6zgo
author_rank: Super Contributor
timestamp: June 19, 2020, 03:03:24 am
content: Quote from: SilverSolder on June 18, 2020, 02:28:49 pmThe process was perfectly OK till somebody broke the existing rule & allowed non-conforming cable sheathing into the system.

author: SilverSolder
author_rank: Super Contributor
timestamp: June 19, 2020, 03:40:50 am
content: Quote from: vk6zgo on June 19, 2020, 03:03:24 amThe process was lacking approval mechanisms, checks, and balances - it was flawed by allowing it to happen. (It's not as if "somebody" snuck out at night and did this covertly, right?)

author: SilverSolder
author_rank: Super Contributor
timestamp: June 19, 2020, 01:41:44 pm
content: Some days, one simply shouldn't have gotten out of bed!

author: rsjsouza
author_rank: Super Contributor
timestamp: June 19, 2020, 03:21:23 pm
content: I remember oncealmostmaking that mistake. I had designed a board for a huge MC68HC11K4 device (a beast in Ceramic PGA packaging with EPROM) and the PCB fab couldn't deliver in time before my trip overseas. Since these were the 1990s, international shipping was not as ubiquitous as today and the board took several weeks to arrive at its destination. When it arrived there, I put the device on the board for assembly and realized it was mirrored - I froze for about a minute or so thinking that I would simply leave the room, go back to my country and never see these people again (this had caused a severe delay on the project already). When I gathered my senses back together, I saw the board was in fact correct and I was the one that was fitting the device in the opposite side - back in the day, silk screen was a luxury we couldn't afford (university project with bare funds).

author: SilverSolder
author_rank: Super Contributor
timestamp: June 19, 2020, 04:35:19 pm
content: Quote from: rsjsouza on June 19, 2020, 03:21:23 pmThe feeling of relief must have been immense, LOL!

author: rsjsouza
author_rank: Super Contributor
timestamp: June 20, 2020, 12:24:20 am
content: The blood had rushed away from my face but the relief was truly immense.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 20, 2020, 04:28:27 am
content: Quote from: SilverSolder on June 19, 2020, 03:40:50 amIn fairness, the grey telephone cable met all the relevant specifications, apart from sheath colour.It is too long ago, but I don't think sheath colour was even specified----- the sheath had "always" been "yellowish beige".If they had insisted on the "right" colour, the usual supplier would not have been able to provide the cable, which would either mean a shortage of cable for ongoing work, or finding an alternate supplier, probably with an increase in cost.There was also more to this than just a "process" internal to Telecom Aust.Telecom Australia was a government run organisation, so when inevitably, the decision had "got out", the "screams & gnashing of teeth" by the media & other agenda driven groups, would have been something to hear:-"Government inefficiency!", "Holding up vital infrastructure due to petty red tape!",-------yada!yada! yada!If they had paid more to an alternative source, the shrieks would have risen to a new crescendo!Meanwhile, TV networks would have found some"poor old lady who had "been waiting for months for a phone installation", even though the reasons for her delay may have had nothing to do with supplies of cable.It would have inevitably have come to the notice of politicians & "question would be asked in the House"!Telecom Aust's CEO would have been dumped on by the Minister, then the blame would have all landed on the person making the original decision.As it happened, the decision to accept the grey cable was made instead, avoiding all the above s**t storm, & for a number of years, turned out to be the correct one.It was only when some installations using grey cable were being stripped out, that the problem arose.In any case, it was one occurrence, & never reached the media.Higher level Management of any company would take that as a result over the alternative, any day!

author: vk6zgo
author_rank: Super Contributor
timestamp: June 20, 2020, 05:13:58 am
content: Quote from: blueskull on June 19, 2020, 10:05:44 amNot electronics, but still in the same vein.Back in the 1960s Holden made a six cylinder engine, where, if you fitted the head gasket upside down (quite easy, as it looked "normal" that way), one of the cooling water jackets would be blocked, the engine would overheat, & possibly be damaged.The MEs were "smarter than the average bear", so they provided a pin on one end of the block, that matched a hole in the gasket, & a recess in the cylinder head, so the gasket could only be fitted one way round.Some years pass, & I'm working on my 1970s Holden, with a later version of the same engine.It seems "someone" had decided that the pin & recess were an insupportable extra cost, so deleted it from the design.I noted this, & made a "mental note", but sure enough, reversed the damn thing!The engine overheated, I pulled the head off, then was called away, came back, & would you believe, reinstalled it reversed!This time, though, just before I finally torqued the head down, I started to doubt myself, so removed it again,----this time, I got it right when I for the third time, installed it.The reason for messing with the engine was that I had a blowup of the original, & had fitted a rebuilt block,-------the head had sustained some damage, but was useable.Some time later, I got a new cylinder head, & repeated the job.This time, I bought an "aftermarket" gasket, & found they had done what should have been done years before:-They provided the water jacket holes at both ends of the gasket, so the thing was fully reversible, allowing any idiot, including me, to fit it!

author: Fred Basset
author_rank: Regular Contributor
timestamp: June 20, 2020, 11:03:51 am
content: Seriously, watch out for self-cleaning ovens. You get even worse burns from them. I got a very brief contact once and it is something I do not ever want to repeat. The coating is made to get so hot in use that the food spatters will not just carbonize like normal ovens, but be oxidized into CO2 over time and evaporate. Works pretty quick on live flesh as well.

author: Fred Basset
author_rank: Regular Contributor
timestamp: June 20, 2020, 11:34:58 am
content: Where would I start? I have made some corkers over the years...My first ever PCB. I never thought to reverse it, I just drew it like the circuit diagram on the board with etch resist pen. It was an op amp tester and quite nice really. when I come to solder the test socket in, that is when it occured to me that an op amp would not be getting voltage on the right pins. So I save the day by soldering everything onto the copper side of the board, and problem solved! Looked so different that I still have it as it was in a clear box. People look at it, and their face goes blank while they work out what is wrong with it...Then I was lay under a table, wiring things in at the bask of the machine on it. I had to solder some things and I picked up the iron by the end that bites you. I yelped and tried to jump up. Not a good escape plan under a table, I practically knocked myself outAlways beware of beginner's mistakes, and doing a neighbour a favour. One day a neighbour came in, in a panic. She had been vacuuming when there was a loud bang, a big blue flash and now it does not work. So I went over, sat on a chair and inspected the cord. Sure enough she had run over the cord and the rotary brush had swept it up into the mechanism where something had stripped the insulation. I showed her, but she backed away from me. I guessed she was still nervous after the big blue bang?"Shouldn't you turn it off first?" she said warily."Eh?" I just had chance to say before the second big blue flash of the day and now there was a hole in the knee of my new jeans. I wondered f my knees really were that white, or was I still seeing stars from the blinding flash?"I thought you said it went bang??" I said fairly calmly (but only because I was still in shock myself.)"it did!""You didn't turn it off?""I left that for you to do! - I did not want to go near it!"I bite my tongue, she did not want to go near it, but happily watched me pick it up...Then me wits stopped jangling enough for me to think of something - If this has had it's bang for the day already, how did it manage to still be alive when I got there? I started opening the plug to see the fuse?"Didn't it blow the fuse when it blew up on you?" I asked as I took the back off."Oh, it did that a while ago she said, but my son fixed it!" She said, trace of pride in her voice. Too ***** late, I had seen that her son fixed the cartridge fuse by wrapping kitchen foil completely around it. I bet that foil was good for at least 50A.

author: Rerouter
author_rank: Super Contributor
timestamp: June 20, 2020, 11:44:47 am
content: Yeah, never trust mains on someone elses word, I cannot count the number of times my mother put the entire blender, electric carving knife or sandwitch press in to the sink while still plugged in and switched on!, filled the sink hearself, then asked me to do the dishes,First time around I was about 7 years old, I got to work, but felt an a odd sensation, then asked my younger brother to come out and verify that something felt weird about the water, making a tingling feeling, I finally noticed to cord,I still have no clue to her twisted logic on that one, why the whole blender, and not just the jug, or just the blades of the carving knife!

author: Fred Basset
author_rank: Regular Contributor
timestamp: June 20, 2020, 12:01:25 pm
content: Quote from: blueskull on June 20, 2020, 11:25:20 amarg...that's horrible! Although "wart Remover" is normally saliclyic acid I believe, so what is the difference between a soldring iron and a chemical burn? Just the thought though...

author: SilverSolder
author_rank: Super Contributor
timestamp: June 20, 2020, 03:15:13 pm
content: Quote from: Rerouter on June 20, 2020, 11:44:47 amSounds like she was stressed!

author: jmelson
author_rank: Super Contributor
timestamp: June 20, 2020, 07:05:28 pm
content: Quote from: Rerouter on June 20, 2020, 11:44:47 amSome people need to be WATCHED CLOSELY all the time when around anything more dangerous than a butter knife!Geez, today that could be enough to get you locked up!Jon

author: SilverSolder
author_rank: Super Contributor
timestamp: June 20, 2020, 07:16:39 pm
content: Quote from: blueskull on June 20, 2020, 04:18:02 pmI'm surprised at that, the techies around here tend to carry pretty cool tools.

author: vk6zgo
author_rank: Super Contributor
timestamp: June 21, 2020, 12:10:23 am
content: Quote from: blueskull on June 20, 2020, 04:18:02 pmI really hate that sort of situation, where you have to "nudge" alleged experts to do what is perfectly obvious.I have had the same problem with the so-called "telephone techs" sent around by Telstra.Although usually nice people, they seemed to have no diagnostic skills, & unless you steered them in the right direction, took forever.In all cases till recently, the result was a compromised repair ------ the line was "still a bit noisy, but usable".Over time, this would deteriorate to "totally unusable".Finally, they sent somebody who knew what he was doing, & removed the lead-in cable coming from the cable pit, pulling a new one in.One tech, maybe 30 minutes work to do what they said needed a "crew of contractors" to do seven years ago.They "forgot" to do it then, leading to all the drama over years!I could have done it myself, but of course, I'm not allowed to!

author: tautech
author_rank: Super Contributor
timestamp: June 21, 2020, 03:26:02 am
content: Quote from: vk6zgo on June 21, 2020, 12:10:23 amAh yes, back in the days when we relied on copper for comms, I had a chat to the telco tech working on our ground pillar addressing the overly noisy phone line we'd called in as a fault.He said it was fixed now and made the mistakeof handing over his tech hand-piece so I could listen how clean the line was now.....dead silent except for a tiny hum.Where's the dial tone I asked him so he hung up and lifted again and pressed a single digit.Ah, is that your test I asked him, yep he replied and any line should be noise free after pressing a digit.For decades thereafter whenever the line hadanynoise we called it in as a fault !Even when our telco fault center went overseas they could still do a line test even while you were on it to them and when inevitably confirmed as noisy they gave you a job # and a guaranteed completion date after which a months free line and phone rental was credited to your account if it was not fixed.Over those decades connected to copper probably a year or more was without charges.It came up the other day in discussion and the SO proudly proclaimed her best run was 6 months straight without a phone bill.

author: Laszlo
author_rank: Contributor
timestamp: June 21, 2020, 04:01:55 pm
content: The first week on my new job I was working on a CL73 locomotive and for some reason, I had to take the emergency brake controller out. Fixed the fault, proceeded to fit the e-brake back to its place, and managed to snap 1 out of the 4 bolts off the top of the handle. It took the pipefitters a whole shift to remove the controller, drill the snapped bolts out and fit the controller back.My manager was not very pleased.The same week, on another loco, I managed to lose a screw from a special relay. Only to find out, that there were no similar screws in the whole factory. I didn't even dare to tell my manager, so I stayed over at the end of shift and shifted through the boneyard until I found a similar screw.I turned out to be okay though, not like my friend who managed to bond the ground points to the HV cables during insulation testing.Good times

author: jwm_
author_rank: Frequent Contributor
timestamp: June 29, 2020, 07:07:29 am
content: Mine involves some high voltage and a lesson about transmission lines.I was working with high voltage to power a photomultiplier tube, on the order of a few kilovolts that had a BNC connector on the supply. (in retrospect, it may have been MHV which has the unfortunate design flaw of being accidentally compatible with BNC cables just feeling like a bit of a tight fit at first.). I needed to run the high voltage a fair distance, longer than any short cables we had but we did have a nice large coil of coax that would reach across the room with some to spare. I wasn't completely clueless so observed a strict policy of the power side of the cable always being the last to be connected and the first to be disconnected. under no circumstances would a dangling end with the other end connected to the supply ever exist at any point during procedures, even if the supply was known to be turned off, no dangling high voltage cables ever. This was all good and strictly adhered to. The tube wasn't installed yet, but we wanted to test the power supply so power things up, use appropriately safety precautions to measure the voltage and current capability where the tube will go and were pleased with the result. Then following procedure I go and remove the cable from the power supply then go and remove it from the tube fixture and start coiling this long ass coax back up. Now, A super long stretch of coax is basically two conductors separated by a very good dialectric, it is a big capacitor. one we just charged up to 3kv and physically disconnected from anything that might bleed off that voltage. Eventually while winding I got to the end and touched the shield and middle pin together and got a hell of a shock. Although the capacitance was probably on the order of nanofarads and I got less than a joule of energy it hurt way more than more energetic shocks I have gotten, but perhaps part of that was due to the utter surprise at being shocked by a wire that wasn't connected to anything, it wasn't even on my mind as a possibility. In any case, I have never since forgotten the C component of the RLC distributed element model of transmission lines. I bit the bullet and invested in SHV connectors and upgraded everything high voltage to use them after that, spent a pretty penny on SHV cables but I was rather motivated.

author: capt bullshot
author_rank: Super Contributor
timestamp: June 29, 2020, 08:58:03 am
content: Not the stupidest mistake I've ever made, but a nice and harmless one (no dangers to humans or animals involved):I was debugging a low voltage power supply for a bit of excessive ripple and a tendency to oscillate under certain conditions. So I made some circuit modifications and watched the results with a scope. Of course, I followed all your "proper probe grounding" etc. stuff, but there still was some noise and switcher ripple that I couldn't get small enough to close the case. To watch the noise and ripple, the scope input was set to AC and mV/div settings were used, as one would do for this kind of work.In the end, I've spent at least one whole day (not) finding the root cause of the noise and ripple until I noticed the probe was set to 1:1 instead of 10:1. Never mind, no one (but me) noticed the delay. Afterwards, I fixed the probe switch to 10:1, and the next set of scope probes I got was 10:1 only (not switchable).

author: aiq25
author_rank: Regular Contributor
timestamp: June 29, 2020, 01:15:08 pm
content: I was working on a 12V to 230Vrms DC-to-AC power inverter. I was checking the temperatures of the PCBA with a thermal imaging camera. There were few hot zones. I decided to touch one of the hot zone (stupid idea, don't remember why, I think I wanted to confirm if it was hot to the touch).... Turned out it was the high voltage H-Bridge and I shorted to the high voltage DC link and got a nice shock from it.Still don't remember why I was trying to touch the hot zone but very stupid none the less.

author: HiSmartAlarms
author_rank: Newbie
timestamp: July 01, 2020, 03:00:18 am
content: Not a terrible mistake, but I was about to make a custom circuit board just to realize that the KiCAD design had the relay connected directly to the power bus (thus making it always be on, which is not really ok when your making a tornado siren controller...)

author: m3vuv
author_rank: Super Contributor
timestamp: July 01, 2020, 02:35:49 pm
content: :--This was actualy true,but i must say in her defence she was a type 1 diabetic and had been drinking so her glucose levels were possibly sky high,should of kept my mouth shut and just thought it to myself,at the time she was doing a lot of swimwear modeling shoots and was totaly obsessed about her weight,at that point i was sick of her whinging about it,well you live and learn!!,or die learning!

author: Achu
author_rank: Contributor
timestamp: July 01, 2020, 04:56:50 pm
content: Mine would be replacing the circuit breaker with a solid copper wire for testing an induction motor I just rewound and accidentally burning up the whole conduit.

author: Sal Ammoniac
author_rank: Super Contributor
timestamp: July 01, 2020, 09:37:00 pm
content: I bought a new development board to develop an application for a new microcontroller. This board was labeled as a "professional development board" and cost several hundred dollars. It was powered via a barrel connector on the board and needed 12V DC. In my haste to get started with this board I pulled out a box of plug packs from the closet and rummaged around until I found a 12V DC pack with a connector that fit the connector on the board. When I plugged the pack into the wall, smoke started pouring out of the board. In my haste to get going I grabbed what turned out to be the only plug pack in the box that had negative on the center conductor and positive on the outer conductor.The board wasn't a total loss, fortunately--I just had to replace a pair of tantalum caps and the board powered up with no problems (after I found a plug pack with the proper polarities on the connector).This next one wasn't due to me, but it's funny enough to include here. On my first job after college I was working on the firmware for a Multibus II disk controller. I found an issue with the board that appeared to be a stuck address line, so I asked the engineer who designed the board to come and take a look. This guy was somewhat of a dandy and liked gold jewelry. He wore a gold watch on one wrist, a gold bracelet on the other, a gold necklace, and several gold rings. He started probing the backplane of the system with a scope probe and as soon as I saw what he was doing, I just cringed. In those days, S-100, Multibus, and VME bus systems typically had 8-20 card slots and were powered by big linear power supplies capable of lots and lots of amps on the 5V and 12V rails. Sure enough, this guy managed to get one of his gold rings across the 12V rail and sparks went flying everywhere. The ring was welded to the backplane and had to be cut off. The short blew the 12V traces on the backplane PCB clean off. Fortunately, I never had to work with this guy again.

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 05, 2020, 05:36:00 am
content: Quote from: Rerouter on June 20, 2020, 11:44:47 amI sure hope that was a "misunderstanding" on her part??? All the same, I am glad you are still around to tell us about it.Being on here, there is a good chance we know a little bit about electricityBut perhaps we overestimate others? When I was a kit, I remember we went on holiday to a seaside flat (in Britain). My Dad and Granddad went out to get something and came back to a very nasty smell of burning plastic. My Mum and Gran had decided to make a cup of tea for everyone, only to find the kettle and stove were electric. They only had gas at home, so they have never even seen electric ones... Sure enough they filled the kettle with water, put it on the electric ring on the stove and worried about all the acrid smoke. When they were asked why they did that, they said it was an electric kettle, so it made sense to put it on an electric stove just like they put a normal kettle on the gas stoves. I could kind of see their logic, but I could also see the stunned looks on my Dad and Grandad's faces.What happened to you could have been fatal though. I once ended up having a great discussion with some authors about the "electric toaster in the bath" scenario. They seemed properly miffed when I had to point out that it is no longer that dangerous. GFIs or similar help if the voltage tracks to earth or neutral, but there is no connection now to earth through baths, since the piping is PVC. Even most water supply piping is PVC now, so it is not quite as deadly as it used to be.This has an intersting corrolary - Dual bonding of the earth connection in the UK (and elsewhere?). Because the water pipes cannot be assumed to be metal anymore, all properties need to be dual bonded to both water AND gas pipes. Suprising how many people are freaked out and call me a liar, because they think possibly connecting voltage to a gas pipe would result in a massive gas explosion.

author: minifloat
author_rank: Contributor
timestamp: July 05, 2020, 09:01:05 am
content: Had to fix a software bug in an automotive ECU involving a diagnostic function of some internal power supply. It was falsely triggering in case of short externally applied undervoltages. So, with a programmable Toellner PSU I applied DC with modulated sinewave on top. So applying sweeps of 10seconds length at 10..100Hz, then 100..1kHz, then 1k..10kHz. Each only 10sec. At some frequency range, the bug came evident. I was observing AC current peaks and the voltage was also peaking AC-wise. Did not spend a thought about the AC current. So, had an idea, quickly coding, recompile, flash.While testing the improved function, now for more than 30seconds, one of the filter caps located after a common mode choke suddenly went POOF and a 1 meter fountain of fishy smelling fumes sprayed into the air.After having the caps replaced and a thermocouple glued to them, 7K/sec in the sensitive frequency range. It is never the voltage alone, it's the current heating up capacitors...

author: dbctronic
author_rank: Regular Contributor
timestamp: July 05, 2020, 01:00:51 pm
content: Tried to check for noise on a 220V mains line when my little old $90 'scope's input was only rated for 100V, just momentarily forgot to reach for the 10:1 probe. POP!!! Oh well, it was a Chinese glass scope, and I very gladly replaced it with a Picoscope which is Star Trek tech in comparison, so all's well that ends well. Still... dumb da dumb dumb!!!!

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2020, 06:41:59 am
content: playing with walki talki near sensitive SA preamp (still not determined!)

author: coppercone2
author_rank: Super Contributor
timestamp: July 06, 2020, 06:44:27 am
content: Quote from: Achu on July 01, 2020, 04:56:50 pmi learned to put projects on a shelf and forget about them if things feel funny

author: TheHolyHorse
author_rank: Regular Contributor
timestamp: July 07, 2020, 09:05:06 am
content: I once connected the RX and TX of the serial port on my PC to a 3v3 micro. Guess what it didn't like that

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 07, 2020, 09:35:37 am
content: when I was a student, I had been given a wooden box with a selection of unregulated outputs on it. In testing a car stereo, I inadvertantly connected the positive to +12VDC, but the negative I screwed into one side 24VAC. They must have been good caps on it, because nothing happened for a while and then suddenly 3 went off like confetti cannons all at the same time, while I was trying to work out why there was no sound from the radiocasette?

author: SilverSolder
author_rank: Super Contributor
timestamp: July 07, 2020, 01:25:12 pm
content: Quote from: Fred Basset on July 07, 2020, 09:35:37 amMight have been good for playing the 1812 Overture?

author: Mr. Scram
author_rank: Super Contributor
timestamp: July 07, 2020, 02:53:11 pm
content: Quote from: blueskull on June 20, 2020, 04:18:02 pmI had better expectations of US electricians.

author: Cubdriver
author_rank: Unknown
timestamp: July 07, 2020, 03:03:23 pm
content: Quote from: Mr. Scram on July 07, 2020, 02:53:11 pmI think blueskull is back in China now, but could be mistaken...-Pat

author: RJSV
author_rank: Super Contributor
timestamp: July 08, 2020, 12:10:01 am
content: Uh, ok then: You are making me think, 1978 (ish), Near E Explosion of HYDROGEN-filled OVEN. It's not my fault that no one got hurt.I forgot to remove a relay bypass jumper, after completing calibration procedure. This lock feature kept the 'Moly Wound' oven from powering up unless that production OVEN had a full vacume inside.Wow was the machinist MAD, as a minor boom occurred, and folks, you don't mess with H2.The oven by the way, had a 120 VAC controller sent thru step-down transformer for 36 VAC high current molybdenum heater wire at very high current. The cylinder was of half inch steel plate, so deadly shapnel could have been launched. 0 injuries, I'm happy to report.From the movie,:. RULE #200:Always check your interlocks!

author: Fred Basset
author_rank: Regular Contributor
timestamp: July 08, 2020, 08:05:25 am
content: That is witty SilverSolder, I like that!

author: jmh
author_rank: Contributor
timestamp: July 08, 2020, 11:23:33 am
content: When I was 11 or 12 (so 1972-ish) I had an old valve radio on a shelf and given the absence of the relevant plug I tied wires to the pins at the back to feed mains to it. Like you do. Of course, one day I reached round the back and unplugged it without thinking - and involuntarily danced across the workshop!

author: dbctronic
author_rank: Regular Contributor
timestamp: July 08, 2020, 06:49:06 pm
content: That old tube/valve circuitry... many of us a bit long in the tooth learnt our 'tronics getting zapped a lot. These here modern day 3v3 kids just don't know...I made a power supply out of the guts of a huge old color TV set given me by a repair shop owner who declared it unrepairable, plus other stuff. Nailed me good a couple of times--once I found myself sitting on the floor with a lot of swirly blackness in front of me.But it unfailingly powered several projects.The standing joke in electronics shops was to charge up an electrolytic cap to 180V or so and leave it lying on someone's bench. Pick it up, and you involuntarily throw it 20 feet!

author: IDEngineer
author_rank: Super Contributor
timestamp: July 08, 2020, 07:05:15 pm
content: Quote from: dbctronic on July 08, 2020, 06:49:06 pmI probably have written this up elsewhere, but I had a similar experience in my high school Electronics lab. I was working on an oscilloscope. Had it on a bench with me sitting on a barstool. A buddy was sitting next to me. I must have brushed across the CRT anode because one moment I was sitting there, and the next I was lying on the floor across the room. Traveled about 8-10 feet and had zero memory of the journey.The mind is a funny thing. My first thought, upon noticing that my view had changed to one of the ceiling above me, was "Where did he get the baseball bat?" That my buddy had hit me with a baseball bat hard enough to blow me off the stool and across the room was the only explanation my brain could come up with to explain the pain my in chest and how I'd moved so far, so fast.

author: phil from seattle
author_rank: Super Contributor
timestamp: July 08, 2020, 10:08:47 pm
content: Not my mistake but when I was about 14 I used to frequent a near by surplus electronics shop. The owner got a batch of really big oil filled caps in and was charging and discharging them, for fun, I guess. Anyway, he took a screwdriver and shorted the terminals. Brilliant flash and the screwdriver wound up welded to the one of the terminals. Left quite an impression on me - especially the look on the owners face when realized he had destroyed merchandise and a perfectly good screwdriver.

author: thinkfat
author_rank: Unknown
timestamp: July 24, 2020, 02:39:08 pm
content: I've got to share a story that happened to a friend and caused him a lot of sweating until we were able to resolve it:I was visiting a friend and it was kind of a nerdy get-together of a couple of fellow radio amateurs discussing packet radio stuff which we were into big time back then. At a point (a couple of beers had been had) one of us wanted to show a nice trick, making a cucumber glow in the dark by hooking it up to mains voltage. So, broke out some test leads, forks, clamps, out on the balcony we went.The cucumber glowed nicely. It also stank. And then disaster struck because the balcony was wet and the RCD tripped. The complete flat went dark. His home file server was out, too.When it came back up it wasn't able to mount one of the hard drives, claimed it could not find the filesystem superblock (this was pre-ext3). And on that drive was a lifetime of software development. Everything. With no (or only an outdated) backup. That's when he started to sweat.Eventually, after a lot of swearing and cursing and trying to recover the filesystem I found that he had created the filesystem on the entire HDD instead of the 1st partition (mke2fs /dev/sda not /dev/sda1) and never bothered to put that down into /etc/fstab. One lengthy filesystem check and a proper mount command later all the data was restored and my friend stopped sweating.Corollary: never trust spinning rust.

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: July 24, 2020, 05:14:18 pm
content: Quote from: thinkfat on July 24, 2020, 02:39:08 pmThe other day I wanted to fill with zeros a pendrive that had become too slow:sudo dd if=/dev/zero of=/dev/sdaOnly that sda was the 1TB ssd and the pendrive was sdb :-(

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 24, 2020, 06:09:44 pm
content: Quote from: GeorgeOfTheJungle on July 24, 2020, 05:14:18 pmI'm noticing a lot of ISO's coming with raw dd instructions now. Russian roulette.

author: ArthurDent
author_rank: Super Contributor
timestamp: July 24, 2020, 06:10:01 pm
content: For as long as I've been repairing equipment you'd think I'd know by now that if you're flicking solder blobs off the iron, you shouldn't be wearing Crocs! I was reminded of that a few days ago and have been reminded of that painful fact every time I've moved my foot since then.

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: July 24, 2020, 06:22:34 pm
content: I found a pre used smoke alarm and I stuck a brand new 9v battery in it and stuck it on my server shelf and forgot about it.Fast forward a couple of years and I hear a low battery chirp. I had no spare battery on hand so I put the thing on my desk and removed the battery to stop it from being annoying. With the battery beside it, it still was chirping. I left the battery on my desk and took the sensor down the hall, two rooms away. Still chirping! And just as loud!After three days I realised that the noise was coming from a smoke sensor on the ceiling right above my head. I hadn't looked up.

author: Nominal Animal
author_rank: Super Contributor
timestamp: July 24, 2020, 07:26:55 pm
content: Quote from: GeorgeOfTheJungle on July 24, 2020, 05:14:18 pmWhy not use an udev rule that creates a symlink per USB mass storage device, say/dev/ext-sdX?Lessee, where did I put mine... ah,/etc/udev/rules.d/99-ext.rules:Code:SUBSYSTEMS=="usb", ENV{DEVTYPE}=="disk", SYMLINK+="ext-%k"Create that file, runsudo udevadm control --reload, and whenever you stick in USB disks (spinny or flash), you'll get a symlink/dev/ext-sdb -> sdband so on. So, when you do ops on full drives, you use the/dev/ext-namesymlink.If you don't like the symlink name, or you want different symlinks for different devices, seehere.

author: dietert1
author_rank: Super Contributor
timestamp: July 24, 2020, 08:57:38 pm
content: When i was a student i made a compact stereo set using parts of an old car receiver, adding power supply, various inputs and the like. It worked well and i used it in my room in the student dormitory. One Monday, when i returned from my parents house, the other students in the same floor didn't have light. I found that my self built receiver had a mains filter cap in front of its first fuse, and that cap had shorted out over the weekend and kept firing the mains fuse. Since they could not enter my room, they were lost for one or two days, i don't remember. And i don't remember whether i told anybody..Take care, Dieter

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: July 24, 2020, 09:26:27 pm
content: Quote from: Ed.Kloonk on July 24, 2020, 06:09:44 pm"with great power comes great responsibility" :-)

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: July 24, 2020, 09:32:41 pm
content: Quote from: dietert1 on July 24, 2020, 08:57:38 pmYeah... "you don't remember"It's ok, it's ok.

author: BradC
author_rank: Super Contributor
timestamp: July 25, 2020, 12:43:35 am
content: Quote from: thinkfat on July 24, 2020, 02:39:08 pmSeriously? Your takeway from that was to blame a rotating drive?Quote from: Ed.Kloonk on July 24, 2020, 06:09:44 pmIt's not the tools fault. dd is perfectly fit for purpose.I tripped myself up recently. I have a GPT formatted drive in my macbook, this has an MBR with the first 4 partitions synced on it to facilitate Windows 7 on partition 3. I went to try a Win 8.1 install but being booted in EFI mode it complained about the MBR. I decided the easy way was to back up the MBR onto a USB stick and zero it.dd if=/dev/zero bs=512 count=1 of=/dev/sdaJob done. Now nothing worked. Boot rescue USB and copy the sector back, except forgetting to *check* the destination. It looked good, had the same number of partitions on it (forgetting that the real destination had *no* partitions on it). So instead I copied the sector over the MBR on the USB stick. The USB stick holds all my backups, plus a great deal of work data (which is backed up, but a day out of date and I'd done a lot of work that day) and of course systemrescuecd.Now I had a laptop that wouldn't boot, and an unbootable systemrescue USB stick. I'm in another location, so this was the only machine I had. My tools were an iPad, Sandisk iXpand USB stick and a wireless router running a cut down openwrt that had a VPN connection to my infrastructure at home, a USB port and a 5 port USB hub.I also had a USB with a Windows 8.1 install image on it, so I spent 3 hours trying to get anything to work on the WinRE environment before realizing I'm either inept or Microsoft are a shower of bastards, and moving on to the aforementioned alternative. I downloaded a heap of software on the ipad and copied it across to the iXpand to try and run it under WinRE (dd, variants of dd, testdisk and a couple of others) but nothing worked due to the limitations of the WinRE environment.So, download systemrescueCD on the iPad and copy it to the iXpand. The iPad SSH client has sucky terminal emulation, so get a VNC client and VNC into a VM running on the infrastructure at home. Fire up the builder VM and add ExFAT, usb-storage and the dependencies to an openwrt config, build it and scp it into the /tmp directory of the router. ssh into router and upgrade the firmware. Plug the USB sticks into the router, ssh back in and mount the iXpand and dd the sysrescuecd image onto a spare USB stick.Luckily I had made 2 copies of the backed up MBR. One on the defunct sysrescueCD USB and one on another spare. dd the spare back to the laptop drive and that booted. The grab testdisk and manually rebuild the MBR on the USB drive.Not fatal, but a bit of hassle to recover. I don't blame the tools for my error however.

author: thinkfat
author_rank: Unknown
timestamp: July 25, 2020, 07:38:34 am
content: Quote from: BradC on July 25, 2020, 12:43:35 amNo, I just liked the rhyme. But still, even though I distorted facts a little for humorist purposes, it emphasizes the importance of maintaining backups and not rely on a single medium to carry all your digital history.

author: BradC
author_rank: Super Contributor
timestamp: July 25, 2020, 02:08:55 pm
content: Quote from: thinkfat on July 25, 2020, 07:38:34 amWith you there. pukcaB should be tattooed on the forehead of anyone receiving their first computer so they see it every morning in the mirror.

author: dbctronic
author_rank: Regular Contributor
timestamp: July 25, 2020, 08:03:02 pm
content: Double with you there! As long as I've owned computers, I have a constant underlying bit of nervous tension directly related to how long it's been since I've last backed up, acquired from running my own business for twenty years. More frequent backups = better sleep, so I do 'em, even now that I'm retired.It astonishes me how many professional people I've known over the years who haveneverbacked up, including shop owners running their businesses on a system! Can'timaginebeing oblivious to that. It's tax time, and 'Cannot read drive C:'. Right.Of course, some of these shop owners were 'running their business on a computer' by dumping everything into a spreadsheet. Nine out of ten spreadsheets in the world are just WYSIWYG databases, which these users typically dump onto paper and tack up to a wall. With that mentality in place, not backing up onto real media is less surprising.And how do I back up my Windows 10 systems? A DOS script using Robocopy. Every backup program I've ever tried issues a summary report that indicates that thousands of files were not copied because they were 'in use by a program' - including myaccounting softwareevery time, thanks very little! I always made sure all other programs were closed when doing the backup. Couldn't get satisfaction from the software vendors. Robocopy just copies what you tell it to copy.Several computer store owners have told me that they do the same, for the same reason.

author: soFPG
author_rank: Frequent Contributor
timestamp: July 28, 2020, 06:05:25 pm
content: After clicking on "import design changes from schematic" in Altium after I already sent the gerber files to JLCPCB (don't know why I did this) I noticed an unconnected net for the power rail and also I forgot to impedance-match USB differential pair.Even though I am 100% certain I did the design rules check and there were no unconnected netsWow, 5€ and 2 weeks down the drain

author: asmi
author_rank: Super Contributor
timestamp: July 30, 2020, 01:52:56 pm
content: Quote from: soFPG on July 28, 2020, 06:05:25 pmOh, I've been guilty of this several times. So I instituted a rule - I only send files for production at least a full day after I hadcleanDRC run on my design, and if I findanythingduring checkup I delay sending it in for another day. It saved many of my "Rev A" PCBs from being a total duds, and they were $200+ orders, not $5.

author: soFPG
author_rank: Frequent Contributor
timestamp: August 01, 2020, 08:00:31 am
content: I just noticed my footprint of a DS18B20 is also wrong because in the datasheet they were showing the bottom view pin designators and I was blindly assuming it was the top view.At least the other footprints are correct

author: GeorgeOfTheJungle
author_rank: Super Contributor
timestamp: August 01, 2020, 10:08:18 am
content: Quote from: soFPG on August 01, 2020, 08:00:31 amBeen there, done that...

author: Psarras
author_rank: Newbie
timestamp: August 02, 2020, 02:05:04 pm
content: Plugging a 5V little lamp into a 230V wall outlet (I thought it wasn't bright enough when power by battery)9 years old back then,great times

author: SilverSolder
author_rank: Super Contributor
timestamp: August 02, 2020, 03:21:10 pm
content: Quote from: Psarras on August 02, 2020, 02:05:04 pmWell, you did probably make it much brighter - just not for a very long time!

author: SeanB
author_rank: Super Contributor
timestamp: August 02, 2020, 04:10:38 pm
content: I plugged a 12VDC lamp into 230VAC as well. To be fair, it was in a box of sale lamps, and was also identical to the 230VAC lamps in the box, being a B22D base and identical glass as well, just the tiny faded print that said 12V 20W on it. It gave a brilliant flash, and the whole shop went dark, because they had literally half the store plugged into a single 16A socket outlet.

author: drussell
author_rank: Super Contributor
timestamp: August 03, 2020, 02:20:21 am
content: Quote from: soFPG on August 01, 2020, 08:00:31 amAt least with small three pin things like a TO-92 with no heatsink, you can usually just flip it around the other way and at least it will work, unlike when you get an IC upside down or something...

author: Mecanix
author_rank: Frequent Contributor
timestamp: August 03, 2020, 03:07:03 am
content: Having my (personal) company recently investing in a high-end EDA software thinking; most (if not all) footprints & components libs should be available as advertised, to find out I'll be the one who need to spend 1,283 years to create my own footprints and model components/libraries so to ensure clearances and tolerances checks out.Dreams & inexperienced high expectations that didn't pay off at the end lol

author: m3vuv
author_rank: Super Contributor
timestamp: August 04, 2020, 09:04:14 am
content: seen the same thing done to a fiat "fire" engine,the gasket had been fitted upside down blocking the oilway to the camshaft,funny thing was tho,it had done about 3000miles like that and still ran but was noisey,fitted a seconhand head and it was fine.

author: jh15
author_rank: Frequent Contributor
timestamp: August 05, 2020, 04:33:05 am
content: I read decades ago an article in popular science/mechanics something like those:Title: Let it fall! Not sure I was even a teen. Years later, I always trained my techs to do that (and myself).Experiment:Roll something harmless but shocking off a table or bench to a male or female.A guy will try to catch it on his lap. A woman will spread her legs in avoidance.In the article grab a soldering iron at it's 800 degree tip as it falls, put your foot under to save a falling 50 lb lathe chuck, etc.Must be be us guys see dollar signs on the tool, not the consequences.Problem in my lab, guys would not try to catch a Tek 7000 series scope from falling/ "Well, you told us so."

author: Ed.Kloonk
author_rank: Super Contributor
timestamp: August 05, 2020, 09:29:13 am
content: Quote from: jh15 on August 05, 2020, 04:33:05 am

author: bd139
author_rank: Super Contributor
timestamp: August 05, 2020, 09:41:22 am
content: Going back to the altium thing earlier, I did a stupid in Kicad a few months back along those lines. Something unfortunately DRC couldn't pick up.1. Throw a board at JLCPCB. £12 order.2. Realise I'd screwed up immediately after submitting the order.3. Spent three hours rechecking the board.4. Submit another JLCPCB order. £12 again.5. Wait two weeks.6. Completely forgot that (2) happened and assembled the board on the screwed up one celebrating victory.7. The day after, the correct boards arrived and made me look like an idiot.

author: Clear as mud
author_rank: Regular Contributor
timestamp: August 06, 2020, 11:00:12 am
content: Quote from: joeqsmith on January 12, 2017, 01:08:32 amThis reminded me of trying to test the fuel pump on an older Honda motorcycle. It had a black and a green wire. Well, I've worked on American cars where black is ground, and German ones where brown is ground, and on neither one is green ground, so I hooked up green to + and black to -. Wrong. Green is ground on this motorcycle. The fuel pump may have been good before!

author: Jan Audio
author_rank: Frequent Contributor
timestamp: August 06, 2020, 12:46:42 pm
content: I did not order alot when prices were low, now a single film-capacitor cost more then 20 cent, it hurts every project now.With low voltage only you can not make stupid mistakes, they just smell.

author: medical-nerd
author_rank: Regular Contributor
timestamp: August 27, 2020, 12:35:06 pm
content: Hiya,Not electronic related but it does make me laugh.Years ago as a student at University in the late 80's while taking time out to do an additional degree, I had a very large Kipps apparatus to generate hydrogen sulphide to stain lead deposits in bone.Well this beast had been left for about 6 months, fully saturated and was time to dispose of the solution.I thought I was doing this is a Fume cupboard, but no, it was a normal dust cupboard connected to the ventilation of the building.Now you might not be aware that exposure to toxic, immediately life threatening levels of hydrogen sulphide is easily done as the sense of smell is quickly overpowered, and you don't smell anything.Anyways, whilst I was wobbling down the corridor, bouncing off the walls - the smell spread throughout the building.It appears that in the library there were suspicious looks at to who had farted. The whole 13 floors had to be evacuated.I was fortunate to survive that encounter to go on and do better (or worse...) things!!!Cheers

author: IDEngineer
author_rank: Super Contributor
timestamp: August 27, 2020, 03:43:13 pm
content: Quote from: medical-nerd on August 27, 2020, 12:35:06 pmMy first question would be: "Why does a dust hood exhaust into the building ventilation system?" Obviously the hood/cupboard is there to control undesirable content (in this case, dust) - why isn't that being discharged outdoors?!?

author: rvalente
author_rank: Frequent Contributor
timestamp: August 28, 2020, 12:52:11 am
content: Did two just this week, i work with industrial automation, was adding some improvements in a machine with two enormous hydraulic brake calipersAfter adding a pick up sensor to the brake rotors I drilled and tapped a hole in the very center of the caliper hydraulic line. Was not funnyTwo days later I wired a autonics encoder in reverse, and that piece of shit has no protection at all, damn thing

author: shapirus
author_rank: Super Contributor
timestamp: March 17, 2024, 01:31:38 am
content: This went unnoticed all the way until the first power-on. Luckily I was cautious enough to first power it from a current-limited supply. And then I had to spray alcohol on the board to see where it evaporates. And even then it took some time to finally notice that it evaporates not only on the 3.3V LDO, but also on this gate, at a much slower rate.I'm glad that I didn't have to wait weeks for this board to arrive from jlcpcb or whatever, as I made it myself.Apparently it was a result of copy-paste + rotate.Lesson learned: don't forget to re-run simulation after adding a new component and don't assume that nothing can go wrong in such a simple case.I wonder if the IC survived. Will check it later.update: it actually simulates just fine as shown. I guess, then, I did re-run the simulation, but it didn't cause any errors. ERC didn't care either. Well, need to pay more attention.

author: tautech
author_rank: Super Contributor
timestamp: March 17, 2024, 04:14:17 am
content: Good practice is to check device pins are assign to a NET then ERC will flag a problem.

author: Messtechniker
author_rank: Frequent Contributor
timestamp: March 17, 2024, 06:30:51 am
content: Not my fault - but wasted some time to find out:Some horrible ex GDR probably BC 550s (NPN) were erroneouslylabelled BC 556 (PNP). Had 100 of them.Handed them over to a school lab. They then used thesein troubleshooting exercises and even in exams.Probably frightened the life out of quite a few students.