hybridfree/eevblog-posts huggingface dataset:
Analog Tone & Probe with Amplifier Troubleshooting - Page 1
Forum section: electronics / repair

author: jdak907
author_rank: Contributor
timestamp: November 21, 2018, 04:37:42 am
content: Hello,I thought that using an off the shelf analog tone generator and test probe might be useful for tracing amplifier circuits. My intended use is on vacuum tube and solid state audio amplifiers, injecting a tone at the input or some intermediate stage of the amplifier and probing along the circuit. Has anyone tried one of these or have any insight on what I am proposing? They really don't offer much information in regards to the specific application I have in mind, but I don't see why it couldn't be used for this.Here is one I was considering:https://www.lowes.com/pd/Fluke-Networks-Analog-Tone-and-Probe/3438412Thanks!Jeff

author: flynwill
author_rank: Regular Contributor
timestamp: November 21, 2018, 04:57:21 am
content: Those devices are intended for tracing communications wiring. They will not be of much use in trying to debug stereo amplifiers. For that you need a normal signal generator and an oscilloscope (and a schematic) for the device you are debugging.

author: jdak907
author_rank: Contributor
timestamp: November 21, 2018, 05:09:15 am
content: I understand what their designed application is, however I don't see any difference in function for tracing audio amplifiers - but I don't know what I don't know. Can you explain why it wouldn't work? I am looking for an audio signal trace... basically inject a tone into the input and check the output stages of amplification devices or certain points in the circuit where there could be noise injected or degradation of signal. I'm looking to use this like a "non-contact" probe.

author: commongrounder
author_rank: Frequent Contributor
timestamp: November 21, 2018, 09:28:59 pm
content: Tone and probe sets are designed for tracing passive, unpowered, wires and cables. The toner signal is relatively strong to cause the wire to radiate an electromagnetic field that the inductive probe can pick up. You really want contact probing for doing signal tracing in amplifier circuits. Inductive tracing will end up leading you on wild goose chases. In theory you could use the toner as a simple signal generator, but you might need to pad the output in some applications to avoid overloading the input stage.

author: floobydust
author_rank: Super Contributor
timestamp: November 21, 2018, 09:37:20 pm
content: Instead, inject audio and use a signal-tracer, a small audio amp with say an LM386 and speaker.You can hear various distortions, lack of bass, loss of signal etc.This is what we used in the electronics repair shop and it works fine and fast to localize problems.Otherwise, injecting a tone requires you use a scope to inspect the signal. A 1kHz sine and square wave can sound similar yet mean a huge difference when troubleshooting.
Replacement Driver for 80 Watt LED Shop Light? - Page 1
Forum section: electronics / repair

author: walkngdude
author_rank: Newbie
timestamp: November 16, 2018, 01:39:21 am
content: Hi,My friend bought 4 10,000 Lumen, 80 Watt shop lights from Rockler.com:https://www.rockler.com/10000-lumen-linkable-4-led-shop-light2 of them didn't work and they replaced them free and told us to keep the defective ones. I tore one of the defective ones down and the driver has nothing written on it except "AC in" and "DC out" nothing else. I checked for power in all the way to the driver and it's good and after the driver there is nothing. I don't have the fixture with me right now but as I remember there are 120 rows of 3 LED's.I opened one of the good fixtures and check the output voltage of the driver and it's 130 VDC.Is there any chance of finding a replacement driver for these things or is this some specialty item engineered specifically for this fixture?It just seems a great waste to throw all those LED in the garbage.ThanksMarc

author: coromonadalix
author_rank: Super Contributor
timestamp: November 16, 2018, 11:29:32 am
content: there is a possibility to find some drivers for them take pictures and list the numbers found on them too ... sometimes the leds pcbs are in serial, i had 32-36 volts pcb's in my tubesI have changed quite a few of them in t5 t8 tubes too, dont forget the leds are controlled in currrent, the voltage may rise or drop a little, 130vdc can be an average ...
Amazon Echo Button Teardown - Page 1
Forum section: electronics / repair

author: GeorgeIoak
author_rank: Regular Contributor
timestamp: November 16, 2018, 02:11:13 am
content: Looking for a 2nd set of eyes if anyone has time. Amazon has these devices called Echo buttons. They're basically a bluetooth button with RGB LEDs. They have an interesting design. To stabilize the top of the device which acts as the button they placed 3 button pads on the PCB in a triangle shape using the common remote control pads with carbon buttonsEach of the 3 buttons are tied together (both halves of the spokes). What's interesting is that 2 of the buttons are connected to a circuit with a few parts, diodes, cap, resistor. The other interesting thing is that they use a bunch of pads that look like they meant to be series resistors but instead the 2 pads have a trace going between themHere's a link to a few photos and a link to someone's page that did a tear down,https://1drv.ms/f/s!Aq7zmueeHqmsgP81wJIQ3wcgA7L-fQAs far as I can tell there's only 1 connection into the MCU for the buttons so perhaps the diodes are some fancy ORing circuit on the 3 buttons? I just keep scratching my head as to why they didn't just use 3 pins on the MCU and use software debouncing. With billions of remote controls using this carbon soft pad for buttons with no debouncing why on this product did they go a little crazy?
Data Precision model 1350 DMM teardown & repair - Page 1
Forum section: electronics / repair

author: intabits
author_rank: Frequent Contributor
timestamp: November 15, 2018, 06:22:02 pm
content: A teardown and repair of a Data Precision 1350 digital multimeter.It's a 3.5 digit from the "budget" end of DP's product line.After some initial stumbling around trying to make sense of internal voltage readings, and chasing down a couple of dead ends, I finallyfind the problem.Total cost for unit and repairs, under AU$20, not a bad result.The video:-The schematic for this unit:-
I need help repairing BMS’s Balancerboard LiFePo4 - Page 1
Forum section: electronics / repair

author: Solartracker2
author_rank: Contributor
timestamp: November 15, 2018, 12:28:46 pm
content: Hello all!,After days searching the web too find useable information I’m so I can repair my BMS system I’m hoping for some luck here.The short version of the story:I bought 4 dead batteries for my Tomos E-Lite escooter. 2 times I made short circuited and have 1 working battery and one left in its original state. Before I screwup my last BMS I need help too repair the two defects.My hope is that someone will help me figuring out which components are which.For more details I trying to upload photos.I can’t upload photo from my iPhone because it is jpeg and not jpg

author: coromonadalix
author_rank: Super Contributor
timestamp: November 16, 2018, 11:36:57 am
content: i think youll have to dismantle the bms and share pictures,,,,,,, and i think you'll have to ask Tomos for an new BMS price or find an used one ?
Hp 3457a AC calibration Error 256. - Page 1
Forum section: electronics / repair

author: Simon Spiers
author_rank: Regular Contributor
timestamp: November 26, 2018, 10:20:05 pm
content: I am attempting another repair on a lovely HP 3457a multimeter that seems to work correctly other than on AC . The self test reveals a Hardware error number 256. The manual tells you to perform a diagnostic run and adjust a capacitor capacitor A3-c332 to bring the count to zero. This adjustment has no effect and the number remains stuck at 4. Has anyone had this problem with the meter before?To me it looks like symptoms of a faulty op amp?Cheers Fellas!
Tektronix 434 repair , dead scope - Page 1
Forum section: electronics / repair

author: Jorge4563
author_rank: Newbie
timestamp: November 14, 2018, 04:17:05 pm
content: Hello guys, I came across this amazing electronics forum and decided to give a shoot to a broken scope to test my skills. I know the 434 is not an amazing scope but it was only 39 dollars and is in excellent cosmetic condition. This scope is the option 1 and is dead. The power supply sounds like clicking, even without load (no boards connected). I have checked the main power transistors and main capacitors. Can i please have some pointers to continue my mission ? I really appreciate any help. I have a multimeter and and LCR meter, as well as some spare caps and resistors.

author: bd139
author_rank: Super Contributor
timestamp: November 14, 2018, 04:34:43 pm
content: Welcome.Have a read of the issues listed here first:http://w140.com/tekwiki/wiki/434Usually I find these sorts of things are shorted caps. Look for tantalum capacitors and check them with a DMM on low ohms. Also the main filter caps tend to go at that age. Worth checking all semiconductors for open/short conditions as well as things tend to cascade fail. Visual inspection first of course!Also to note, some SMPS won't start without a minimum load so this might not actually be the cause - could be a shorting tantalum or something elsewhere that is stopping the supply starting up when connected but also wont start when disconnected anyway.

author: Jorge4563
author_rank: Newbie
timestamp: November 14, 2018, 05:27:23 pm
content: Wow quick response, excellent thank you. Here is a pick of the PSU.
help needed identify zener diode value - Page 1
Forum section: electronics / repair

author: dicky96
author_rank: Regular Contributor
timestamp: November 13, 2018, 01:42:18 pm
content: Hi guysI'm fixing this RGB LED par can nowIt has 3 channels, each channel has it's own DM0565R swicth mode psu, and I assume the DMX controller sets the pwm for each channel,Basically one of the DM0565R has gone bang. So much so that pin2 of the device has completely vaporised. This also took out the fuse, the bridge rectifier and I think was a NTC thermister to prevent inrush currentCurrently I put a wire link instead of the NTC thermister, made a bridge rectifier out of 4x 1N4007 (there is plenty room in the par can housing) and conected via a 60W light bulb in series with the mains. Now two of the DM0565R are running. So I replaced the blown DM0565R and also looked around the components close to that device. I have an open circuit 000 ohm resistor and a short circuit zener.The 000 I assume I can just replace with a wire link.The zener is short so I don't know the rating. It is connected from pin 3 of the DM0565R to Ground and according to the example schematic on the datasheet a 22V zener is suitable. It looks to be an over voltage protection device only.http://pdf1.alldatasheet.com/datasheet-pdf/view/85398/FAIRCHILD/FSDM0565R.htmlsee ZD 101 schematic 1 on page 14. Mine is in the same position in circuit.I could unsolder one from another channel to measuer the voltage rating. I tried to measure in circuit on one of the other channels but the DM0565R kicks on at about 10.5V so I can't get a reading. I doubt it is critical though.The question is what is the Wattage rating supposed to be? It's a little 0805 (I think) cylindrical SMD device. There are no marking on it.Also how do I select a suitable NTC? The original is blown to crap.Photo attached but the camera on this phone is crap and I left my better phone at home lolAny advice??

author: dicky96
author_rank: Regular Contributor
timestamp: November 14, 2018, 12:59:03 pm
content: No one?Here are some better pics if that helps. The zener is on pin 3 (Vcc) of DM0565R to hot Ground.

author: stj
author_rank: Super Contributor
timestamp: November 14, 2018, 05:03:33 pm
content: i would meter a good one.i would also clean the filth off the board and work out why the screws are rusty as F.if you get filth on the board, and then it traps moisture - well that's when shit can happen!
GPU - Black screen flickers on monitor. - Page 1
Forum section: electronics / repair

author: parryaddiction
author_rank: Newbie
timestamp: November 19, 2018, 02:31:24 pm
content: Hello Guys,I have a MSI GTX 970 4gd5t ocGPU that was repaired recently for a faulty mosfet chip.It worked fine for some time but now while running my pc the monitor goes black for 2-3 seconds and come back.Sometimes the PC gives the error that GPU drivers recovered successfully. Other times nothing. This happens randomly either Iam watching youtube/chrome or idling.Ive tried everything via software(GPU drivers removal and new installation etc). It doesn't seem the problem is in the software as this happens in the BIOS screen too.What can be the problem you guys think?Also where can one find board schematics for GTX 970 cards?Any help will be appreciated.
HP G42 458TU Battery Drain - Page 1
Forum section: electronics / repair

author: sabareeshchambayil
author_rank: Newbie
timestamp: November 13, 2018, 11:22:57 am
content: My hp g42 458tu laptop is always in powered condition( i mean its shutting own ,but dvd drive harddisk etc are working) . If I kept battery in laptop full charged it will be drained with in 1 day and its a new battery.At first I thought it would be related to windows 10 ,so I checked removing harddisk and same thing happened.So I checked by removing battery ,harddisk and plugged adapter and pressed DVD drive and it's working without pressing power button, and display color is changing to dark and white(like flikering without back light)I am ready to repair this myself (I mean chip level)I have all the accessories and tools for repair and I disassembled laptop but no components seem to be visibly damaged.i Dont know where to start.Board ID is DAAX1JMB8C0 REV:Ci got the schematic for this model by a google searchAny help will be greatly appreciated.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 14, 2018, 12:10:53 am
content: Are you sure its totally shutting down or its the sleep / hibernate ....... in the power plan management check the settings for the power button, i've seen tons of time the power button settled to sleep / hibernate instead of a complete power down ... killed lots of batteriesRun : controle.exe (classic control panel) / power options / select your plans settings / and go to the change xxx settings
Breakway header with strange pitch - Page 1
Forum section: electronics / repair

author: 17_29bis
author_rank: Regular Contributor
timestamp: November 09, 2018, 07:01:21 pm
content: Hello,I am trying to repair a 1 mile car alarm remote that consists of 2 boards - logic and RF (CC1020 based) one. I need to make a adapter for easy swapping of RF boards (borrowed the second RF board and should returned it later) but the original connector seems to have an usual pitch - 1.1 mm - this type of connectors is not available from DigiKey and other reputable online sources, they offer only 1 and 1.2 mm pitch connectors.So, what I am dealing with? An unusual connector or wrong pitch measurement (meaning that I am looking at 1 mm pitch header)?Thanks!

author: Ian.M
author_rank: Super Contributor
timestamp: November 09, 2018, 08:12:26 pm
content: The vernier caliper reading looks like 5.4mm measured across the outside of five pins. However that has one more pin width in it than 5x the pitch. If you measure the thickness of one pin I'd bet it will be about 0.4mm, so after subtracting that you'll have 5mm for 5 pins so the connector is 1mm pitch.

author: 17_29bis
author_rank: Regular Contributor
timestamp: November 13, 2018, 04:59:53 am
content: Quote from: Ian.M on November 09, 2018, 08:12:26 pmUnfortunately that does not seem to be true. I ordered 1mm pitch male/female headers and they are too small as shown on the following picture. So, 1.2mm pitch is too big, 1mm pitch is too small. How could it be?

author: Habropoda
author_rank: Regular Contributor
timestamp: November 13, 2018, 06:03:27 am
content: There are four gaps, not five; so subtract one pin width and divide by four. Fudge in a possible pebcavc error and it's probably the common 1.27mm (.05 inch) header. Lots on Digikey and elsewhere.

author: Ian.M
author_rank: Super Contributor
timestamp: November 13, 2018, 09:54:08 am
content: Whoops - I committed a classic fencepost error.1.27mm (0.05") is very plausible - I doubt plastic vernier calipers are accurate enough to distinguish that from 1.25mm pitch over a short connector*. Its easy enough to check - you must have something that's 2.54mm (0.1") pitch you can compare with, (e.g. a new DIP IC) and under a good magnifier, the middle and outer pins of your 5 in connector should line up exactly.* Even if its is 1.25mm pitch I doubt it will matter over five pins due to the hole tolerances. e.g. 2.5mm pitch ICs as produced by the USSR semiconductor industry were only incompatible with the western 2.54mm (0.1") pitch ones in higher pin counts like memory chips and CPUs

author: tkamiya
author_rank: Super Contributor
timestamp: November 13, 2018, 03:44:59 pm
content: Japanese makers also used metric version. I've seen 2mm and 2.5mm pitch. This was in 80s. It wouldn't surprise me if there are half pitch of those.
Blocked SC-7000Z - Page 1
Forum section: electronics / repair

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 11, 2018, 02:53:32 pm
content: My beloved SC-7000Z seems blocked... the stainless wire won't go more than about half way down.I've twizzled and moved the wire in and out and do get some fine black dust but not enough to shift the blockage.Any hints?

author: JFJ
author_rank: Regular Contributor
timestamp: November 11, 2018, 06:44:30 pm
content: Quote from: NivagSwerdna on November 11, 2018, 02:53:32 pmIs the end of the wire blunt? If so, then filing the end to a chisel shape, and using it like a bradawl, might be more effective. Alternatively, if the narrow bore is only at the nozzle end of the iron's tip then, with the tip removed, it may be easier to clean from the other end (perhaps, using a fine drill bit twisted between your fingers).

author: NivagSwerdna
author_rank: Super Contributor
timestamp: November 11, 2018, 08:54:49 pm
content: I think I have created a new alloy half way down the nozzle.... really need to follow instructions in future and make sure it is clean between uses.I found a supplier of spares so might just go for that.An expensive mistake!

author: Gyro
author_rank: Super Contributor
timestamp: November 11, 2018, 09:23:58 pm
content: Try running an appropriate thickness piece of copper wire down instead - it transfers heat to the blockage a lot better than stainless steel.

author: rodd
author_rank: Regular Contributor
timestamp: November 11, 2018, 11:32:17 pm
content: I had this problem a long time ago and my recollection of the solution is the following:1- remove the nozzle from the body of the tool.2- hold it with a plier while heating it in a gas burner. (I used the main burner of my stove).3- introduce the inox tool in the nozzle (use another plier for that) and force it inside until the obstruction is gone.Enviado do meu iPhone usando Tapatalk

author: CJay
author_rank: Super Contributor
timestamp: November 12, 2018, 03:03:26 pm
content: Keep at it, if you're really stuck you might be lucky with a thin drill bit but my experience with them was that once they block they will keep on doing it unless you can get every trace of the blockage gone.
Tektronix 453 Bulb Replacement - Page 1
Forum section: electronics / repair

author: Feath3rblade
author_rank: Contributor
timestamp: November 11, 2018, 06:23:35 am
content: I have an old Tektronix 453 that works great except for one thing, B568 has a broken lead that prevents me from using the single sweep mode. I don't really want to chase NOS components but if anyone has any ideas on how to replace specifically B568 it would be very much appreciated.

author: dave_k
author_rank: Frequent Contributor
timestamp: November 11, 2018, 09:24:05 am
content: Why does it have to be NOS?The parts list says it's just a A1D neon bulb, available at DigiKeyhttps://www.digikey.com/products/en/optoelectronics/lamps-incandescents-neons/101?k=neon%20A1D

author: Feath3rblade
author_rank: Contributor
timestamp: November 11, 2018, 05:34:03 pm
content: Oh, thanks! Never thought to check to see if they actually still made those.

author: dave_k
author_rank: Frequent Contributor
timestamp: November 12, 2018, 12:01:40 pm
content: Glad to (hopefully) help.Let us know how your progress is going.
Mastercraft DMM #052-0055-6 bad lead plug-in switches (Pictures) - Page 1
Forum section: electronics / repair

author: cdnmatt
author_rank: Newbie
timestamp: November 10, 2018, 01:49:11 am
content: https://www.canadiantire.ca/en/search-results.html?q=052-0055-6Mine looks different, they change them ever couple years for giggles. Mine has 3 buttons under the screen, on/off, light and data hold. I've added pictures for your convenience.This meter was not making sound for diode check, but it did if I pressed down on it, I thought it was a fuse at first, but it was just a spring lever button for the lead plug-in. The ground just does not have a lever, its the second from bottom. The others are momentary switches - The probe lead stays down with the banana connector. The switches are very small, but the detent is good. As you see two levers broke off.How can I remedy this situation, which way is best?I was thinking to unsolder the momentary switch and use a latching push button switch SPST type of appropriate size. Then drill a hole in the plastic.Or bring some colored wires out from the pcb, from the corresponding cover holes.Superglue on some levers might be a good start I think. They do need to be a bit flexy, so maybe scratch that idea.You see the bronze pads in an "I" shape near the diodes, spring and 2 reds, those are the backside, so they must be electrically touching then the switch does something as well, perhaps. Very interesting!Today, I did purchase an auto ranging dmm Mastercraft #052-0052-2 on sale for C$28.There was an OWON B35 on Amazon, but thats $50usd which is C$68. Of course the dot CA site lists it for C$90 shipped.Fleabay is a bit cheaper.I will see if they have the exact same one that I have in the store. Lifetime Warranty if I am not mistaken.

author: cdnmatt
author_rank: Newbie
timestamp: November 12, 2018, 04:42:18 am
content: These are the best pictures I could get.I jumpered both ends and even pressed the button but nothing.
sun mga 1200 gas analyser unlock - Page 1
Forum section: electronics / repair

author: davesaab
author_rank: Newbie
timestamp: November 10, 2018, 09:12:24 pm
content: hi there i don't know if anyone can help me ,today i purchased a 4 gas analyser sun mga 1200 and it was not working,i replaced a few pipes stripped the pumps down cleaned and now I'm not getting LOF lack of flow great fixed,the problem i have now its asking for service this is a Mot thing these can be switch off does anyone know how to do this or they have a unlock code cheers Dave
Sunny Boy 4000TL maybe over voltaged - Page 1
Forum section: electronics / repair

author: Simon
author_rank: Unknown
timestamp: November 10, 2018, 08:19:20 pm
content: I was having solar installed, All going well with getting the panels up there and then we came to plug in. The open circuit voltage on the panels was 550-560V, the inverter is DCmax 550, apparently not a problem. As this is a second hand inverter I do not know it's history other than it had generated 4MW up until I got my hands on it but it ran fine with 6 panels.Well after 3 goes the first producing a pop, the second nothing the third time with 546V at plug in a flash and a bang and two TO263 packages had exploded simultaneously.Should this have happened? is it worth fixing?

author: Simon
author_rank: Unknown
timestamp: November 10, 2018, 08:23:27 pm
content: To clarify a new 8.2KW inverter that takes up to 800V has been ordered, I don't plan to reuse this right now. Everyone is so embarrassed and pointing the fingers at each other that I'm getting it trade with a free install and I guess in the height of summer with 4.05KW of panels facing one way and 3.85KW facing the other with the sun overhead at midday I may output a lot more.There was also a heated debate about if this inverter was man enough for the job.

author: MrMobodies
author_rank: Super Contributor
timestamp: November 10, 2018, 08:37:50 pm
content: I have got one of those with the Sunny Webbox data logger.You can do all sorts of adjustments to like the start and cut off the voltage, frequency and country selection.I get voltages of around 600v on each bank and it has a got loud fan in it.I suspect it could be the setup from the previous installation that might have something to do with it.Was the fan okay when it worked?

author: Simon
author_rank: Unknown
timestamp: November 10, 2018, 08:54:07 pm
content: The fan never needed to work. i ran it fine on 6 panels so AC setup was correct and I think it is the DC side that has failed.
Help me identify fuse location - Page 1
Forum section: electronics / repair

author: EVGAdrifter
author_rank: Newbie
timestamp: November 12, 2018, 11:09:35 pm
content: Could some help me identify the location of fuse F3 and F7? the layout of the text on the PCB isn't helping. Long story short i am trying to find the backlight fuse on lenovo x1 carbon 3rd gen laptop, I believe its either fuse F3 or F7.

author: ataradov
author_rank: Super Contributor
timestamp: November 12, 2018, 11:18:49 pm
content: I'm thinking those components with two white lines parallel to the capacitors (positioned vertically).

author: coromonadalix
author_rank: Super Contributor
timestamp: November 13, 2018, 12:24:08 am
content: not sure but the black dot under the F3 F7 writings, you have 2 unpopulated pads and he's placed under them, you have an rather large pcb trace going to it ?

author: ArthurDent
author_rank: Super Contributor
timestamp: November 13, 2018, 01:31:41 am
content: Capacitors are generally beige or greyish and resistors are generally black. Fuses generally have a white ceramic body color. I can't tell from the photo but what is the device right above the 'D' in 'D63'? Could we see more of the board? It's hard to tell what the white thing in the upper left near the red and black wires is. The component above D63 seems a little small for a fuse.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 13, 2018, 02:08:00 am
content: or maybe the two near the q33 markings ? normally smt fuses are easily spottable, can you do an zoomed out photo ?

author: JFJ
author_rank: Regular Contributor
timestamp: November 13, 2018, 11:56:00 am
content: On the 2nd generation version of your laptop, the F3 fuse is more clearly marked:Its marking is two white stripes - the same as in your picture:

author: drussell
author_rank: Super Contributor
timestamp: November 13, 2018, 12:56:54 pm
content: My first thought was the same as whatJFJmarked up in the posted graphic:Quote from: JFJ on November 13, 2018, 11:56:00 am.. since everything else in the area that are whitish looks like they're all similar looking capacitors. The two marked components are the only things in the vicinity that look a bit different.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 13, 2018, 09:29:39 pm
content: wow never saw thoses kind of fuses, im learning, are they good or open ??

author: tehmagicsmoke
author_rank: Contributor
timestamp: November 14, 2018, 06:52:05 pm
content: Test those components with the white marks for 0 ohms. That'll confirm it.

author: ArthurDent
author_rank: Super Contributor
timestamp: November 14, 2018, 09:08:33 pm
content: Do I get a prize for being the first one with the right answer?

author: Ice-Tea
author_rank: Super Contributor
timestamp: November 14, 2018, 10:09:52 pm
content: Perfect illustration of my credo: if you can't manage to put clear and unambiguous ref designators on your silk screen: don't bother.Piss poor job.
Epson l220 motherboard problem - Page 1
Forum section: electronics / repair

author: StoneBakerMan
author_rank: Newbie
timestamp: November 10, 2018, 01:36:28 pm
content: Hi there i have a epson l220 printer thats not powering on i tried replacing transistors(a2222 & c6144) on the motherboard it turned on for a second but then again turned off the transistors are burned again can you guys help me what should i do about it thanks
Problem with clamp meter (Benning) - Page 1
Forum section: electronics / repair

author: mplksnt
author_rank: Newbie
timestamp: November 09, 2018, 09:24:57 am
content: Hello guys!I have a digital clamp meter (Benning CM 1-2, I have uploaded two photos of the pcb board) and it has two problems:1. The Clamp meter's two cables are disconnected from the PCB board and I don't know where exactly to solder them. However I have seen two possible pins on the board (I marked them with a red circle) that might be the right place for the two wires2. The device does not turn on. Even with new batteries, when I turn it on nothings happen in the screen.I have uploaded two photos. Have you any idea?Thank you very much in advance
Keithley 237 - Page 1
Forum section: electronics / repair

author: Mrusseau
author_rank: Newbie
timestamp: November 08, 2018, 03:00:20 pm
content: I have a Keithley 237 that has a strange problem. I fixed the +/-30V supply (dry voltage doubler caps). In the I Source V Measure mode it is in tolerance for all current ranges except the 10mA range. Has anyone seen this before? I have schematics but it's not really clear the path of the current flow for that range. Also, the unit reboots on occasion.

author: coromonadalix
author_rank: Super Contributor
timestamp: November 08, 2018, 11:29:46 pm
content: Can you post a link to the schematics you have ? is it this one :http://www.ko4bb.com/manuals/104.157.197.231/Keithley_236_237_Source_Measure_Unit_SMU_Service_Manual_and_schematics.pdfI only saw the 236_902_01D.pdf document ? no schematics in it, but there is an brief description of the voltage and current feedback circuits, maybe you have some switching section errors ?And a thread for the 236 :https://www.eevblog.com/forum/testgear/keitley-236-teardown-and-review/msg791944/#msg791944The first link seems very completeYou have to check all the voltages if they all are in compliance, careful you have an +/-1200 vdc section (page 129)Maybe some gentle taps on the cpu section could tell you if you have cold solder joints who reset the cpu
Electric fence ATVA-4 repair - Page 1
Forum section: electronics / repair

author: xoom
author_rank: Regular Contributor
timestamp: October 26, 2018, 09:08:18 am
content: Hi trying to fix this device.. it have blown BD911 transistor (hes TAB touched HV wire insulation and melted it) so i guess it got high voltage.. tryed to replace with similar transistor but its not working (not oscillating).. drawn schematic from it and it looks strange:dont know how it supposed to oscillate..can somebody bit explain how this topology works?

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 26, 2018, 10:09:10 pm
content: There are 2 oscillators, one on the left xformer to reach something around 400-600V from 12V, then a low frequency oscillator that discharges the 15microF 700V cap into the right transformer giving a few kV pulse on the output.Step-up is something along these lines:BD911 is biased into conduction through R1,R2 and the small secondary winding on your schematic.Once enough current has flowed through the primary winding, a voltage will show on both secondary windings, the smaller windings being in reverse on the BD911 base will stop it's conduction until field in transformer is insufficient, then cycle repeats.BC547 is there for voltage regulation, limiting BD911's conduction once secondary voltage is high enough.220nF is either there for setting oscillation frequency or as capacitive voltage dropper for charging the reservoir cap. (Less heat dissipation)The time constant for the fence pulses is set by R5 and 10microF cap, once diac voltage is reached a pulse occurs then the 15microF cap must charge again.For testing you can isolate the 2 functions by breaking the circuit after the 15microF cap. If voltage ramps-up there you have problem on the pulse side.

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 26, 2018, 10:19:12 pm
content: Similarly you should be able to test the pulse side by charging the 15microF cap through a resistive or capacitive dropper from the grid, with or without voltage doubler depending on your grid voltage.In either case 12V or grid supply be aware that the 15microF cap is the enemy (besides grid of course), far more dangerous than the fence output.

author: shakalnokturn
author_rank: Super Contributor
timestamp: November 08, 2018, 05:51:50 pm
content: Another repair that went wrong... We're loosing members... Need a sticky "Safety rules" in the repair section!
Service Manuals/Schematics for Cyberpower UPS OL1500RMXL2U?? Any sources? - Page 1
Forum section: electronics / repair

author: rx8pilot
author_rank: Super Contributor
timestamp: November 15, 2018, 05:20:29 am
content: Digging into an old-ish Cyberpower UPS that periodically (every few hours) faults out with beeps and an LED indication. The manual simply says 'UPS FAULT' which of course is not helpful.The batteries are brand new and in general, it works normal, until the fault shows up a few hours later. I don't think that I have much of a chance to track this down without a block diagram and schematic. Hopefully some description of what faults will trigger this error.Has anyone ever found schematics for these units?
Tektronix 2225 CRT Problem - Page 1
Forum section: electronics / repair

author: DarKnightSP
author_rank: Newbie
timestamp: November 07, 2018, 06:26:35 pm
content: Hi,I'm trying to buy a second hand oscilloscope and I'm interested in this Tek 2225 for around 100€. It has decent pricing and decent specs for what I could find here in Spain where the market is really small for this products. The owner showed me a video of it working but i'm afraid that it has some big problem with the crt as you can see in the video. I want to know if this is a common problem with an easy solution or just a "don't buy it" sign.Thank you.https://youtu.be/4YNPxCtyo3wEDIT: Turns out the instensity was set to max and the signal showing was really slow. It show likes this now:I think there is no problem with this scope. But maybe you notice something wrong. What do you think?

author: tautech
author_rank: Super Contributor
timestamp: November 08, 2018, 04:46:53 am
content: Quote from: DarKnightSP on November 07, 2018, 06:26:35 pmWelcome to the forum.Yep trace rotation is miles out.Grab the service manual from here and make sure it can be rotated back to where it should be before buying it.http://w140.com/tekwiki/wiki/Main_Page

author: DarKnightSP
author_rank: Newbie
timestamp: November 08, 2018, 10:22:09 am
content: Quote from: tautech on November 08, 2018, 04:46:53 amThank you! I also noticed the trace rotation but that will be easily fixed. Not any more visible problem, right?

author: tautech
author_rank: Super Contributor
timestamp: November 08, 2018, 11:11:15 am
content: Ah, the crack !Well if you can live with it and it doesn't effect performance and the price is OK and good scopes are hard to find......well your choice !Glue, patch and screws/bolts = Franken scope.

author: bd139
author_rank: Super Contributor
timestamp: November 08, 2018, 11:24:43 am
content: They're good scopes when they're working. Check all the switches on the front panel carefully though as they are 100% totally unobtainable if they are worn. Donor scope is literally the only option.Weak points are HT intensity pot, transformer and switches. Any of those die and you need a donor unit. Parts are simply not available.On a positive note they are mostly made of completely standard and easy to obtain parts, the board is good quality and the service manual is good quality too.Edit: also power supply has Philips axial capacitors in them. Those will be the first suspect if anything dies in it down the line.

author: DarKnightSP
author_rank: Newbie
timestamp: November 08, 2018, 11:42:46 am
content: Yes, the crak! I think I will try to repair it when I have more time available. Also the scope seams to need a deep clean.The switches appear to work fine, the owner has showed me a video while he changes intensity, focus, vertical and horizontal scale and also triggers. There is another 2225 for sale that is in better external condition but the owner asked 280€ and although I got him to drop it to 170€+shipping, that is over my budget.I will report back when I have this one in my own hands.Thank you for your help!
HP 3586 Error Message - Page 1
Forum section: electronics / repair

author: RCHRDM
author_rank: Regular Contributor
timestamp: November 10, 2018, 04:13:06 pm
content: I have an HP 3586 Selective Level Meter. On startup, it shows an error message "CE - p." I can override the message by pressing the "MEAS CONT" key, but the message returns.The service manual says that this may indicate that board A20, 20 Hz Filter, may be the problem. I pulled the board out and checked it visually and cleaned the edge connector, but it made no difference.Can someone suggest what might cause this error?Richard
SAMSUNG WE 1048 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: November 06, 2018, 04:38:21 pm
content: Good evening everyone! I have an external hard drive whose hard drive was dead. I replaced it by the same one as the original, but it is not recognized on the tv and the computer. What should I do for it to be recognized? Does it have to be formatted with software? I work under windows 10 64 bits. Thank you for you precious help!

author: lionelkjh
author_rank: Frequent Contributor
timestamp: November 06, 2018, 04:38:59 pm
content: the following.....

author: Rasz
author_rank: Super Contributor
timestamp: November 06, 2018, 06:38:23 pm
content: looking at amazon it doesnt look like hdd, more like a media player so yes, most likely you need the software that was on the diskhttps://www.amazon.co.uk/WE-Art-multimedia-hard-drive/dp/B00D9KRL78

author: coromonadalix
author_rank: Super Contributor
timestamp: November 06, 2018, 09:21:13 pm
content: Sometimes they are not formated to be windows compatible, some tv boxes, Videotron hd recoreders, Bell hd recorders are specially formatted, sometimes they are linux look a like partitionsIf you dont know how the old hdd was partitioned, or the kind of formating , you may be out of luck
Salee Logic 8: Can someone please take a voltage reading here - Page 1
Forum section: electronics / repair

author: Psi
author_rank: Super Contributor
timestamp: November 03, 2018, 09:18:23 pm
content: Hi,If anyone out there also has a Salee Logic 8 would it be too much to ask for a voltage reading here?Trying to repair a faulty one.Also if anyone can identify this IC that would be cool too.It's a 5 ball BGA and probably a switch-mode voltage reg.Marking looks like is Line1= 31 Line2= KThanks a lot!

author: artag
author_rank: Super Contributor
timestamp: November 04, 2018, 02:33:55 pm
content: I've got a pro 8. It's not quite the same, but it does appear to have something very similar - see ttt's pictures athttps://www.eevblog.com/forum/testgear/saleae-logic-pro-8-quick-teardown/https://www.eevblog.com/forum/testgear/saleae-logic-pro-8-quick-teardown/?action=dlattach;attach=112275;imageSeems like a regulator towards bottom right, just below the flash chip. Mine has markings Line1=33 Line2= .cIf you can work out which point is the equivalent, I'll measure that.Also - have you contacted Saleae ? I don't know what their repair policy is but I've always found them incredibly helpful. They might just replace it for you. Of course, that's not as satisfying as repairing it yourself.

author: Psi
author_rank: Super Contributor
timestamp: November 05, 2018, 10:43:01 am
content: Thanks, I'll have a look and see if i can figure out which reg matches the same reg on your one.Yes, i have contacted them and they have been amazingly helpful. Salee is a great company.but I might as well try to fix this old one though.

author: KL27x
author_rank: Super Contributor
timestamp: November 06, 2018, 03:18:05 am
content: I have the original, probably the first few months they were available. I don't remember it being called an "eight" back then. The covers shows a picture of a chip, "logic," and the company website.If you think it's the same model you have, I will see about getting it open. I thought I had my hex bit game in order, but these hex heads are smaller than anything I have.

author: Psi
author_rank: Super Contributor
timestamp: November 06, 2018, 05:49:17 am
content: Thanks for everyone's help.Salee had shipped me a replacement a few days ago (because they are just that awesome)This morning the replacement arrived and they asked for the dead one back, which is totally understandable.So there's no longer a need to attempt repair on the dead one.Thanks again
Tektronix 7834 instability when vertical amplifier overdriven - Page 1
Forum section: electronics / repair

author: ycui@eml.cc
author_rank: Newbie
timestamp: November 04, 2018, 07:45:08 am
content: I have a 7834 for quite some time, and it works mostly OK. However, recently I found a very subtle problem with it.To describe it. I need to measure a very small noise on top of a large DC signal. I have 7A13 which is supposed to handle this type situation. If I connect the internal 4V square output into 7A13 and set the vertical scale to 1mV/div, I can observe the display readout moves up and down. The display readout was perfect as long as all the trace stay within the display. They will move crazily as soon as trace go out of display.So, I am suspecting when the vertical amplifier goes into overdrive condition, the +15V power rail loss regulation and cause the CRT vertical amplifier gain change, which manifest into readout display moves up and down. So, I hope a re-cap of the switching power supply should fix the issue.I also have a 7613, it does not have this problem when I overdrive 7A13 plugin.Can anyone confirm my suspicion?

author: David Hess
author_rank: Super Contributor
timestamp: November 06, 2018, 12:36:31 am
content: Usually this is caused by thermal imbalance in the vertical amplifier chain. When the differential amplifier signal chain is driven into saturation or cutoff, one side dissipates more power than the other increasing the offset voltage.Sometimes it is caused by leakage through the vertical channel switches.Some of the 7000 mainframes have a thermal balance adjustment but I do not think the 7834 does.
More scope shenanigans - Page 1
Forum section: electronics / repair

author: Zenwizard
author_rank: Regular Contributor
timestamp: November 02, 2018, 02:30:30 am
content: I have mostly finished up a 7603 mainframe scope for the bench and got new probes in for it today. It is nitpicking but it has an odd quirk when the readout is on it looks like there is static on the trace. Readout is rock stable. I think I have isolated the fault to the readout board. Attached are some shots from my other scope. The weird thing is when the readout is on the clock on U2126 is no where near stable. When readout is OFF. trace is smooth as glass no static. The service manual is not to clear on this or I am just not totally understanding what it is trying to tell me.Thanks for the help.

author: tggzzz
author_rank: Super Contributor
timestamp: November 02, 2018, 07:52:24 am
content: Quote from: Zenwizard on November 02, 2018, 02:30:30 amThat statement would be a lot more useful with a picture of the "static", whatever that is (e.g. X/Y/Z axes). Is it at all sweep rates?Consider that the electron beam has to draw the characters, and during that time it cannot be displaying the trace. That can cause trace intensity variations at some sweep speeds.

author: Zenwizard
author_rank: Regular Contributor
timestamp: November 03, 2018, 03:23:12 am
content: It is a Z axis fault. Attached are 2 photos one is with the readout off the other is with the fault present. It is almost like the blanking circuit is firing randomly. The fault is the dark spots on the trace. Also they are not stable they scroll through the trace but they do not exist on the readout display.

author: drussell
author_rank: Super Contributor
timestamp: November 03, 2018, 03:51:47 am
content: Quote from: Zenwizard on November 03, 2018, 03:23:12 amLiketggzzzsaid, are you sure it isn't just artifacts from when the scope draws the on-screen characters? Does it change when you vary the sweep speed?Presumably the timing for the on screen display of characters is not timed to the sweep speed so will not always occur at retrace time or anything...

author: duak
author_rank: Super Contributor
timestamp: November 03, 2018, 10:04:05 pm
content: I'm pretty sure those are artifacts from the readout. The beam has to refresh the readout at a minimum rate and it becomes visible at certain sweep speeds. At slow speeds, the gaps are too small to see while at fast speeds, the readout refresh is interleaved between sweeps.

author: David Hess
author_rank: Super Contributor
timestamp: November 06, 2018, 12:20:08 am
content: The beam is multiplexed to generate the readout so at some sweep repetition rates when the readout is free running, the multiplexing becomes visible in the trace and this is completely normal.There is a switch on the readout board which controls when the readout multiplexing takes place. In GATE TRIG'D mode which is suitable for photography, the readout is generated at the end of the sweep but in this mode, there is no readout unless the sweep is present. Some of the other 7000 mainframes have this control on the front panel.
lcd fading digits - Page 1
Forum section: electronics / repair

author: pete g
author_rank: Regular Contributor
timestamp: November 04, 2018, 10:33:32 pm
content: hi all, I have a dmm that is missing a digit. it is not a fluke unfortunately. my question is, is there a universal elastomeric or do you need to use the one for that particular brand and model?

author: lowimpedance
author_rank: Super Contributor
timestamp: November 04, 2018, 11:33:13 pm
content: Perhaps a cotton tip moistened with some IPA to gently clean the strips and the PCB contacts for the elastomer strips will improve it. Worth a try, BTW what brand of meter is it?.

author: floobydust
author_rank: Super Contributor
timestamp: November 05, 2018, 12:55:50 am
content: Zebra strips are uniquely sized for the LCD display and enclosure.I've had success soaking them in hot water, and stretching a bit, to re-soften them.

author: pete g
author_rank: Regular Contributor
timestamp: November 05, 2018, 02:11:56 am
content: hi, its a meter I've had for a long time. brand name jdm instruments. how about my question, do you need a specific elastomeric strips for the meter or are there universal ones?

author: lowimpedance
author_rank: Super Contributor
timestamp: November 05, 2018, 03:22:33 am
content: Do you have a universal type in mind?The originals could be sized to fit the application in you meter but also it may be possible the manufacturer just purchased off the shelf ones too and cut to size !.I cannot say whether universal ones will work or not but if you can find cheap universal ones that look similar give it a try. Unlikely to be an issue, either work or it wont !!.The flip side of course is the meter actually worth it, maybe its time to look into something new as you now have a reason.

author: pete g
author_rank: Regular Contributor
timestamp: November 05, 2018, 07:51:27 pm
content: hi, I did get 2.5 digits to work. I think i'll settle for that. kinda like this old meter. thanks for the response.