hybridfree/eevblog-posts huggingface dataset:
Bizarre SD card behaviour - Page 1
Forum section: electronics / repair

author: AKM
author_rank: Contributor
timestamp: May 20, 2016, 07:52:34 am
content: I got this craptastic MP3 SD card player to put some music on it.I turned it on, and there was some American 60s music on it.Plugged it via mini USB cable to PC, nothing happens.Took out the 2GB SD card and put it into an Orico card reader/USB hub, it is empty.Put some music on it, put it back in the player, only the 60s music can be played.Put my SD card from my old Nokia phone, it plays music from the card like it should.Do a quick format (FAT) on the bizarre SD card on the PC, put it back in the player, again only the 60s music can be played.Put the bizarre SD card into the old Nokia phone, it says only 1 GB and has a lot of folders with unintelligible folder names.Do a normal format (FAT) on the PC, put it back into the player, no more 60s music.Put some music on it (mixed 128kbps, 320kbps, V0 MP3 files), nothing plays.Put the bizarre SD card into an LG phone, it sees and plays the songs normally.Copy a 1.6GB movie onto the bizarre SD card, movie plays normally on the PC.Test the bizarre SD card with ChkFlsh, PASS.Put the bizarre SD card into the old Nokia phone, won`t open it, just initializes it indefinitely. But shows 1GB total size, with ~800MB used, 1GB free.Format the bizarre SD card on the old Nokia phone, it now sees 1.86GB total size, 1.86GB free.Put some music on it and into the mp3 player. It works like it should.Do a normal format (FAT) on the PC, put some music and put it back into the player; everything works normally.WTF?

author: SaabFAN
author_rank: Frequent Contributor
timestamp: May 20, 2016, 09:07:27 am
content: Maybe it is a fake card, reporting more memory than acutally available, or just a crappy controller inside of it.

author: AKM
author_rank: Contributor
timestamp: May 20, 2016, 09:12:18 am
content: The size is alright, 2GB(1.86GB).I copied a 1.6GB movie on it and played back without any problems.It passed Check Flash 1.16 test without any problems.My biggest question is why did the format on the old phone fix the issue, but format on the PC didn’t. If I format it now on the PC, it works.

author: dexters_lab
author_rank: Unknown
timestamp: May 20, 2016, 09:47:23 am
content: IIRC windows obfuscates the partition information on flash media like thati've had problems before with windows not formatting flash cards & usb drives properly

author: botcrusher
author_rank: Regular Contributor
timestamp: May 20, 2016, 11:30:11 am
content: The official SD card flashing utility normally does it right on the first try, on mobile so i don't have a link right now. A quick google will find it for any future craptastic sd cards

author: CJay
author_rank: Super Contributor
timestamp: May 20, 2016, 11:53:15 am
content: I've had weirdness where a card wouldn't format in a PC to full capacity using Windows or the SD association formatter (even with size adjust, diskpart etc.)The quickest way to get around it was to drop it into a digital camera and format it in that, full capacity and readable afterwards
Oscilloscope probe sleeves - Page 1
Forum section: electronics / repair

author: akis
author_rank: Frequent Contributor
timestamp: May 20, 2016, 07:54:43 am
content: I have a bunch of scope probes in very good condition but I have melted/destroyed/lost their sleeves that have that little hook+spring and latch onto things. Where can I buy a bunch of them from? To save me from buying brand new probes.

author: tautech
author_rank: Super Contributor
timestamp: May 20, 2016, 08:22:54 am
content: Probe ends do have different diameters so you'll need to check yours, they might not all be the same.There's this lot on eBay:http://www.ebay.com/itm/5pcs-New-Oscilloscope-Scope-Clip-Probe-Hook-gray-for-Tektronix-Probes-/162026766635?hash=item25b98c412b:g:Di8AAOSwgApXAFw5But for that money you can buy 3 new P6100 probes.
HP 34970A self test fail - ideas needed - Page 1
Forum section: electronics / repair

author: WangQi
author_rank: Newbie
timestamp: May 17, 2016, 03:21:50 am
content: Recently got an "as it is" HP 34970A from ebay. The original lithium battery is dead and I replaced it with a 3V CR2032. It did power on but failed in the self test reporting 6 ERRORs 609,610,611,617,618,621 which indicates some problem on the DMM board.The DMM board seems intact and no obvious sign of failed components. All the voltage rails are OK, +/-10V ref are accurate, A/D converter seems to have perfect waveform when input is zero(see AD_CTRL) .I also captured the waveform of the input buffer's (input scaling circuit) output during the self test, the output levels seem correct to me, at least for test items 609,610,611,617,618(I marked the test pulses with test item# - apparently the numbers are also used as the error code, see self test).I don't have a MUX module yet so haven't done any real measurement. I'm completely lost in terms of the next step of debugging.Anyone has some ideas?The full schematic and error code description are also attached.https://doc.xdevs.com/doc/HP_Agilent_Keysight/service/34970A/34970-90012_svc_Part_2.pdf

author: plesa
author_rank: Frequent Contributor
timestamp: May 17, 2016, 05:33:31 pm
content: Did you check functionality of U101, it is shared between gain setting and ohm current source. Without relay card it can be difficult to test properly.

author: WangQi
author_rank: Newbie
timestamp: May 17, 2016, 06:28:50 pm
content: According to the waveform of test items 609,610,611 seems U101 works normally - able to control the gain.

author: simmconn
author_rank: Regular Contributor
timestamp: May 18, 2016, 07:11:25 pm
content: The DMM board can be tested by rigging something up on its input connector. A multiplexer card is not absolutely necessary in debugging it. My 34970A came with 617 error (plus a couple of others that I can't remember). It turns out the AD706 was bad. The previous owner must have injected high voltage into the Ohm range. Despite the protection circuit sometimes the opamp does go bad. After replacing the opamp the unit passed self-test. That was long before I came across my first multiplexer card cheaper than what I paid for the switch unit.Just follow the service guide and schematics to debug. There is enough information in there. And pray that the big analog ASIC didn't go bad.

author: WangQi
author_rank: Newbie
timestamp: May 19, 2016, 09:16:06 pm
content: Thank you for your suggestions. But without the relay card I'm not able to get any readings from the device.What's confusing is based on the self test waveform, the signal feeds to the multi-slope A/D is correct (e.g 609=0.7V,610=7V,611=18V) but it still reports error 609,610,611. The only reason seems to be the A/D is not working properly. While test item 612,613,615 pass which indicates the A/D is working properly...
Solartron/Schlumberger 7081 calibration key - Page 1
Forum section: electronics / repair

author: JFJ
author_rank: Regular Contributor
timestamp: May 18, 2016, 05:01:58 pm
content: If anyone has an original calibration key for a Solartron/Schlumberger 7081, 7071, 7061 or 7062 meter, then please can you tell me the key's number (three digits stamped on the side of an original key)?A friend may be able to source a new key for me - from a stock of Honeywell/Micro Switch AML 20 series keylock switches, but they need know the key's number.

author: ManateeMafia
author_rank: Frequent Contributor
timestamp: May 19, 2016, 03:06:35 am
content: One side is stamped "Micro Switch USA"The other side "601". In smaller print (in one corner) is "HV61".

author: JFJ
author_rank: Regular Contributor
timestamp: May 19, 2016, 06:00:00 pm
content: Thank you for that information, it proved extremely useful.There were no "601" numbered keys in the keylock switch stock. However, a Google search for "Micro Switch 601 HV61" achieved a positive result. It found an eBay seller offering new AML key switches, complete with two "HV61 - 601" keys, all for about the price of having a single spare key cut (and without the need for an original key to copy).
Help with a PCMCIA port not working anymore on an Amiga 1200 - Page 1
Forum section: electronics / repair

author: amigalover
author_rank: Newbie
timestamp: May 17, 2016, 10:40:24 pm
content: Hi all!I follow the youtube channel, and did realize only now that there is also a site and a forum; way to go Dave!I have an ancient A1200, from Commodore. It is the PAL version, and after so many years I decided to take the motherboard out, due to lack of space, to make a smaller desktop unit.Unlucky for me; while moving the board in the new case, I forgot to remove the PCMCIA-to-CF adaptor from the board, and this caused a damage to the PCMCIA plastic guides. I did use superglue to fix the broken piece of plastic, but the PCMCIA port does not see anymore any CF card; and often it reboot the Amiga.I do not see anything broken on the mainboard; so I am not sure what did I damage when I broke the plastic tab of the PCMCIA port. Does anyone have any suggestion about what to look for? I am handy with electronics, I did build kits, but I am in no way a hardware technician, so if you could suggest me what to look for and where; it would really be appreciatedFrom a previous conversation with another Amiga fan, he suggested to check the connection points on the motherboard, going from the PCMCIA connector, with the multimeter, but he never told me what to look for...like for specific voltage? For connectivity?Thanks in advance!
amplifier  - Page 1
Forum section: electronics / repair

author: w
author_rank: Newbie
timestamp: May 17, 2016, 03:34:17 pm
content: Im attempting to repair a car audio amplifier but i cant seem to find the input transistors the number on it is t460 and theres one other component but idk what it is the number is es1d

author: klr5205
author_rank: Regular Contributor
timestamp: May 17, 2016, 03:45:11 pm
content: A google search with some wildcards yielded the mosfet below... are you sure you're not looking at anoutputtransistor?Is it shaped like the one shown here? Are there any other markings on the package?http://www.digikey.com/product-detail/en/alpha-omega-semiconductor-inc/AOT460/785-1146-5-ND/1855918

author: w
author_rank: Newbie
timestamp: May 17, 2016, 07:10:18 pm
content: I am not entire sure but that looks to be it.
philips 32ta2800 won't turn on sometimes  - Page 1
Forum section: electronics / repair

author: sony mavica
author_rank: Frequent Contributor
timestamp: May 22, 2016, 01:25:12 am
content: my mums tv has been having problems in the last month when i plug it in and the standby orange light comes on then turns blue as soon as tv boots up turns straight off againbut sometimes if i unplug the tv leave it for a while come back latter and try again sometimes it will boot up as normal and work 100% finecan anybody tell me what could cause this problem and would it be an easy fixif i am unable to fix or its going to cost too much ill will probably just sell it really cheap for parts and get my mum a crt tv (my mum is happy with any tv as long as she can still watch tv) till she saves up money to get a new tv

author: tautech
author_rank: Super Contributor
timestamp: May 22, 2016, 01:51:15 am
content: More than likely bad caps, SMPS primary and secondary sides.Primary side suspect the controller bulk cap ~20-50uF and any/all on the secondary side.Visual inspectioncouldeven let you spot them.Just a simple DMM capacitance check should show up any culprits that are 10% lower than labeled values and need ditching.ESR checks are better still but only if you have one.
Repairing a network cable tester: The magic smoke has been released! - Page 1
Forum section: electronics / repair

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: May 17, 2016, 01:20:26 am
content: So at least something is totally fubar on this thing.The line sniffer thing works but its really quiet.The cable tester does not work. When in scan or test, it does this:So I opened up the main unit (sniffer's cable test side is just a board with leds and resistors) and I found a blowhole on a little tiny package in the middle:VERY faint LEDs on the main unit for the first couple leds. 4 and 5 stuck on on either mode on the sniffer side.Where to go from here? What was the blown part? I am sure I have a motherboard I can steal one from like I did with my asrock motherboard when it blew up a sot23 mosfet.

author: TheMG
author_rank: Frequent Contributor
timestamp: May 17, 2016, 04:53:14 am
content: Looks like it's the same as Q4, with the marking "J1Y". From what I can find, that should be a 2SA1298 PNP transistor or equivalent. Nothing special. Should be easy to find a replacement. Hopefully the microcontroller isn't damaged.Anyways, if you have no luck fixing that piece of garbage and you do a lot of work with network cabling, I'd recommend this guy:http://www.flukenetworks.com/datacom-cabling/copper-testing/MicroScanner-Cable-VerifierA bit on the pricey side of things (then again, nothing Fluke is particularly cheap), but it is a handy device that does so much more than those cheap cable testers. It's saved me tons of time at work troubleshooting network drops. Faults that might have taken an hour to trace down with a regular/cheap cable tester I've been able to find and repair within minutes with this thing.And unlike the cheap units, you can safely plug it in to a live network (even with PoE), live POTS line, etc and it won't blow up.

author: iamdarkyoshi
author_rank: Frequent Contributor
timestamp: May 17, 2016, 01:35:20 pm
content: Quote from: TheMG on May 17, 2016, 04:53:14 amI hardly do any networking. Just stuff at home. My existing tester makes this one look like a piece of professional equipment...Anyway, thanks for the help, I will try bodging something in place, and maybe break out the rigol osmelloscope to see where the pixies are dancingAnyway this thing was a craigslist freebie, so I am not super concerned if I can fix it or not. If nothing else the sensor probe entertains the cats when they touch the sensor
Source for replacement piezo buzzer? (Fluke 117) - Page 1
Forum section: electronics / repair

author: iXod
author_rank: Frequent Contributor
timestamp: May 12, 2016, 05:22:50 pm
content: Piezo died in Fluke 117.Where can I source a replacement piezo buzzer? Fluke no help.Cheers.

author: iXod
author_rank: Frequent Contributor
timestamp: May 16, 2016, 04:22:34 am
content: New info:There is no signal going to the piezo. Removed the Piezo, scoped the pads and enabled 2 modes (Non-Contact Voltage Detect; and Continuity) but nothing seen.Traces go back to CD4069UBC hex inverter. Here's the mind-bending thing to me: an inverter is connected *across* the piezo:There are no other connections to the piezo's pads (ie, on the flip side of the board). The many vias at the top of the board is part of the non-contact voltage detector.Am I losing my brain? When is it good design sense to put an inverter across a piezo? What the...?Cheers.

author: Gyro
author_rank: Super Contributor
timestamp: May 16, 2016, 09:11:46 am
content: Connecting an inverter across a Piezo is normal practice to improve its volume - one side goes up, the other side goes down, effectively doubling the voltage swing. Your problem is whatever is failing to feed the inverter with a signal.I notice that you have double posted this thread in the Test Equipment section too. That's never a good idea because people end up answering both of them and it gets annoying. I suggest you terminate one of the threads (probably this one as several people have answered the other one), and change the title to 'MOD please delete'. The other thread is:https://www.eevblog.com/forum/testgear/source-for-replacement-piezo-buzzer-%28fluke-117%29/

author: iXod
author_rank: Frequent Contributor
timestamp: May 17, 2016, 05:23:50 am
content: duplicate post.

author: vbalint
author_rank: Newbie
timestamp: May 17, 2016, 09:50:14 am
content: I suppose the 4069 forms an oscillator with the R49/R50/C34 and it is also a driver. I'm pretty sure that the pin 6 of the 4069 is connected to the pin 9. From pin 9 an inverter is also driven which outout is pin 10. An interesting detail is that the GND of the 4069 is switched with Q11.If the buzzer is otherwise good it is most probably the 4069 what went wrong.
Tektronix 466 Scope Issue - Page 1
Forum section: electronics / repair

author: alco539
author_rank: Newbie
timestamp: May 10, 2016, 12:10:36 pm
content: A couple of years ago someone gave me a Tek 466 scope. It initially powered up and appeared to work just fine. However before I could really use it and check it out good the 15 volt power supply either died or something is pulling it down. Any ideas where to start looking or where to get the proper schematic for it. I was able to find the ones for it's cousin the popular 465 which was pretty close but not exactly the same as this is the storage version of the 465.Thanks for any assistance.Jimmy

author: AF6LJ
author_rank: Unknown
timestamp: May 10, 2016, 12:41:54 pm
content: Try this page....http://w140.com/tekwiki/wiki/Main_Page

author: MrSlack
author_rank: Frequent Contributor
timestamp: May 10, 2016, 12:45:43 pm
content: AFAIK it's pretty much the same piece of kit as the 465. If it's not a B rev, the service manual is here for the 465:http://www.opweb.de/en/model.php?id=2968- the other versions of the SM appear to be incomplete.Diagnostic procedure on these (I have three 465B's and am juggling them a lot):1. Check the rail voltages using the test points on the board. The range and tolerance is in the service manual. You can check ripple with a half decent multimeter set on AC volts.2. Check all electrolytic and tantalum caps for shorts. There's a nasty wet tantalum at the base of the A4 board that likes to explode as well as some on the vertical board that like to snuff it.3. Check all bridge rectifiers on the A4 board.4. Check the MC1458 op amp at the base of the A4 board.5. Check the power transistors at the rear of the unit for shorts.The 15v rail is referenced on the 55v rail so make sure that's working first.

author: alco539
author_rank: Newbie
timestamp: May 10, 2016, 12:57:12 pm
content: Thanks guys. I haven't needed it since I got it so I really haven't been too motivated to look at it. I now have a need for it and wish I had looked at it earlierHopefully I will get i nailed down in the next few days.Thanks again.Jimmy

author: alco539
author_rank: Newbie
timestamp: May 16, 2016, 05:23:53 pm
content: The problem turned out to be a shorted tantalum cap on the 15 volt rail. I swapped it for an electrolytic I had and it is working beautifully now.Thanks for the help.Jimmy

author: tautech
author_rank: Super Contributor
timestamp: May 16, 2016, 08:48:31 pm
content: JimmyFor the sake of completeness for anybody finding this thread it'd be a good idea to list the cap part # and the values.

author: alco539
author_rank: Newbie
timestamp: May 16, 2016, 10:43:37 pm
content: No problem,I should have included that information in the first place.C3462, a 6.8ufd tantalum on the Vertical Preamp board.Jimmy

author: MrSlack
author_rank: Frequent Contributor
timestamp: May 17, 2016, 07:45:29 am
content: Glad to hear a positive outcome
Agilent MSO-X2012A turns one every other time I push the button - Page 1
Forum section: electronics / repair

author: craftycoder
author_rank: Contributor
timestamp: May 13, 2016, 08:44:37 pm
content: Every other time I press the power button on my Agilent MSO-X 2012A it turns on just two LEDs and freezes. The next time I power it up it behaves as expected. I ran the hardware self test, all good. Any thoughts?

author: Len
author_rank: Frequent Contributor
timestamp: May 13, 2016, 09:09:37 pm
content: Quote from: craftycoder on May 13, 2016, 08:44:37 pmSounds like a power supply problem to me. I've seen similar behaviour on a PC, after a while it just wouldn't turn on at all. It turned out to have a bunch of dead electrolytic capacitors.

author: tautech
author_rank: Super Contributor
timestamp: May 13, 2016, 09:30:16 pm
content: Quote from: Len on May 13, 2016, 09:09:37 pm+1PSU is where I'd look first, especially for ripple on any of the rails.Don't discount dead local caps on the MB either......a PC MB I recapped not long ago displayed exactly the same symptoms and some of the MB caps got so hot they hurt to touch.

author: craftycoder
author_rank: Contributor
timestamp: May 16, 2016, 12:34:25 pm
content: I'll crack open the case and take a look with a thermal camera. The warranty expired 6 months ago. Amazing how well Agilent can design to out live the warranty.

author: nctnico
author_rank: Super Contributor
timestamp: May 16, 2016, 01:11:24 pm
content: I'd start with reseating all the connectors.

author: craftycoder
author_rank: Contributor
timestamp: May 16, 2016, 03:14:44 pm
content: I cracked open the case and found that the main 420V 100uF nichicon cap was hot and the device had not run all weekend. Presumably the "switch" is a soft switch and the PSU has been running a lot more than I assumed. Note to self, unplug DSO when not in use!

author: AndyC_772
author_rank: Super Contributor
timestamp: May 16, 2016, 03:33:07 pm
content: Yes, it's a soft switch. Quite why is anybody's guess.Dave mentioned it in his video review of these scopes; the standby power consumption is surprisingly high.

author: tautech
author_rank: Super Contributor
timestamp: May 16, 2016, 03:39:16 pm
content: Quote from: craftycoder on May 16, 2016, 03:14:44 pmDon't go ripping stuff out until you've checked values are to spec, personally I'd suspect the SMPS controller IC power supply chain....either the resistive dropper from rectified mains or the small bulk capacitor on the IC power rail, normally 20-50uF.The IC datasheet will list what voltages are needed for the SMPS to kick off at and the UVLO voltage, make sure both are maintained.

author: craftycoder
author_rank: Contributor
timestamp: May 16, 2016, 04:10:13 pm
content: No noise to speak of coming out of the 13V supply. All the low voltages look good at first glance. Seems like it just forgets how to boot up half the time.
buzzing choke - Page 1
Forum section: electronics / repair

author: anda
author_rank: Newbie
timestamp: May 15, 2016, 02:10:48 pm
content: Hi!I have this line filter choke in a small curcuit for 230v. It sits in series with the 230v leads. The thing is that it is making a buzzing noise like a bee which is amplified even further when the pcb is in its casing.So is there any ways to make a buzzing choke silent?Is there any danger in leaving out a line filter choke. Can the curcuit do without it?

author: Monadnock
author_rank: Contributor
timestamp: May 15, 2016, 02:41:44 pm
content: To reduce buzzing, chokes are usually varnished or potted. You can get small volumes of varnish on ebay. Or you could try potting it with epoxy.Don't know the geometry of the choke, but it can also help to space the choke off the PCB a little so the noise isn't conducted directly into the PCB which can act like a speaker.You can also leave it out, the circuit will just send more noise onto the line.

author: TheMG
author_rank: Frequent Contributor
timestamp: May 16, 2016, 03:46:59 am
content: Clear nail polish/varnish is a common, easy, and relatively cheap way of silencing noisy chokes.Quote from: Monadnock on May 15, 2016, 02:41:44 pmMuch to the detriment of anyone in the vicinity trying to receive ham radio, shortwave, or AM broadcast. Don't do it!Filter chokes are there for a reason and if the manufacturer included it, that's because it probably wouldn't pass EMC compliance without it.

author: Trakehner1
author_rank: Contributor
timestamp: May 16, 2016, 11:17:27 am
content: Soak it in varnish, any company that makes transformers can do it for you. If choke doesn`t get hot, you can use standard varnish from a store, soak it twice and it will be fine.
Fluke 187 intermittent error - Page 1
Forum section: electronics / repair

author: Mr. Pete
author_rank: Newbie
timestamp: May 14, 2016, 02:37:56 pm
content: Hello all,This is my first post in this great forum.I have on my desk a Fluke 187 with a weird fault, I want to have it fixed because it is my favorite meter, and I like to fix and learn. I bought it a few years ago second handed, so no free Fluke repair I guess. It measures within specifications on all functions, except on the mAAC setting. I'll describe it's problem measuring a constant current of 1.001mAAC (+/-0.5%) from a precise current source on the mAAC setting. The measurements are checked with other more precise and recently calibrated meters, and I can say confidently that the current source is accurate enough. This Fluke 187 is specified to have a maximum deviation of +/-0,75% and +/-20counts measuring 1mAAC on the mAAC setting, so it should return a value between 0,973 and 1,029maAC.After power-on the returned value varies between 1.040 and 1.060mAAC, which is out of specification and it varies from time to time. While attempting to find a solution for this problem I recently discovered this. Twisting the multimeters housing with force by hand, the value can be made to drop to 1.018mAAC and it remains stable at that value for the rest of the power-on status. This value is now comfortable within its specification. Rotating the function knob back and forward a few times and back to the mAAC setting, the reading stays accurate. It can be made faulty again by twisting it again. Once re-powered, the value always starts faulty, until a forced twist of the housing is performed again. The intermittent fault has clearly a physical nature.All the other measurement setting are stable and accurate, twisting the housing or lightly smacking the dmm does not influence any reading at all. Extra attention was given to the mADC, uAAC and uAAC measurement range: all are always stable and accurate.I have removed the pcb from the meter. It looks good and clean, no signs of abuse, I have not seen any broken solder points etc. The rotating function knob contacts are clean as are the pcb traces underneath. My guess is a faulty coupling capacitor or resistor network somewhere on the pcb transferring the ac signal for the the mAAC setting only. If only I had acces to a circuit diagram... My reverse engineering capabilities are not very well developed for these kind of circuits.Does someone here have an idea what components are involved in this specific measurement (mAAC) only? Or any specific ideas what to look for? Or maybe, am I overseeing something here? I measure mA's in the range of a few mA's quite a lot. It would be nice to have this functionality back on this meter.Regards, Pete

author: lowimpedance
author_rank: Super Contributor
timestamp: May 16, 2016, 02:47:23 am
content: Wonder if there is a hairline fracture in the current shunt area etc. with the cover off and inputing a suitable current can you carefully prod (with a suitable tool !) the areas around the current shunts 'and them too' while looking for fluctuations in readings.
Battery acid corroded circuit board - Page 1
Forum section: electronics / repair

author: lyk93
author_rank: Newbie
timestamp: May 15, 2016, 01:56:06 pm
content: Hi all,I have a logitech n305 keypad that is corroded by battery acid (alkaline i think).I have dissolved the acid crystals with vinegar and baking soda mixture and wiped the board with alcohol.However, when I insert batteries the keypad doesn't power on.I tested for continuity as suggested by other forums and there is continuity in the circuits.Please advise on what else can I do. Someone recommended me to bake the board under heat to try to revive the board but I'm not sure what is right as I have little experience with electronics repairthank you

author: mikerj
author_rank: Super Contributor
timestamp: May 15, 2016, 07:35:30 pm
content: Depending on how long the PCB was exposed to the leaking battery, you may have open circuit vias or tracks. The picture is too small to see clearly, but it looks like some of the tracks are discoloured, if so you should check the track for continuity with a multimeter.

author: Ian.M
author_rank: Super Contributor
timestamp: May 15, 2016, 07:47:57 pm
content: First you need to remove ionic contaminants. Soaking and scrubbing with hot water with a trace of dish detergent is about as good as you can get if you don't have an ultrasonic cleaning tank. Rinse twice with deionised water, then with IPA and air dry for a week or 24H with moderate heat and forced ventilation.Positive tracks usually get corroded away by electrochemical action. Start from the battery positive and follow it looking for breaks, pins or metalisation corroded off components etc.
Delongh primadonna s6600 grinding time too short  - Page 1
Forum section: electronics / repair

author: Pressing multilayers Do I
author_rank: Newbie
timestamp: May 15, 2016, 05:07:53 am
content: Can anyone think of what would cause this, given that everthing else works on the machine.I would think the cpu does the timming for grinder duration.thanks.

author: sleemanj
author_rank: Super Contributor
timestamp: May 15, 2016, 05:34:26 am
content: Is it too short because it's just always been too short?Is it too short because it's lately become shorter?First case: that's how they made it, almost certainly a function of the microcontroller, have you consulted the manual to see if it's configurable?Second case: it's possible that the timing is based on the charge time of a capacitor which has lost it's capacitance and is therefore charging (or discharging) too quickly.

author: Muttley Snickers
author_rank: Unknown
timestamp: May 15, 2016, 05:51:31 am
content: We have the Delonghi Magnifica and the timing of the grind is set on a dial inside the bean hopper and not in the program settings although yours maybe slightly different but the manual for yours indicates the same thing so check this first, I hate these machines as they are a nightmare to clean and don't get hot enough for our liking so we have switched back to instant coffee for these reasons.

author: Pressing multilayers Do I
author_rank: Newbie
timestamp: May 15, 2016, 06:43:22 am
content: Thanks for the replys.It could be a cap .that would be a stupid design by delonghi since its microcessor controlled.The used machine($3000new) was given to me. previous owner said that grind time on the extra strong setting "on the display" was originaly 8 sec now its 2 sec.Also the grind setting dial adjusts the particle size not the grind timefiner grind is more tightly packed.Im not ready to crack the machine open yet because it still makes coffee.

author: Muttley Snickers
author_rank: Unknown
timestamp: May 15, 2016, 08:24:39 am
content: See I would have thought that a finer blend simply required more time getting crunched up than a coarse mix and that's pretty much how it reads in the manual for ours and also what I discovered on other sites although some mentioned that there could be a problem with the grinder itself being loose or the cutters worn out.We are all out of beans so I cannot properly test this theory although I am half tempted to fill the thing with rocks just because I can, as mentioned earlier it might simply be a component failure but after seeing a few pictures of these machines in bits and looking like a toxic dogs breakfast as you said leave it be or switch to tea.

author: Pressing multilayers Do I
author_rank: Newbie
timestamp: May 15, 2016, 10:52:17 am
content: I do drink tea but im sort of hooked on coffee at the moment.but i will run it till it dies
Brightgreen DR700 MR16 Retrofit Failures  - Page 1
Forum section: electronics / repair

author: Craig
author_rank: Newbie
timestamp: May 15, 2016, 06:15:04 am
content: Like others, I'm starting to get a collection of Brightgreen DR700 MR16 (12V Input) Retrofit LEDs that are failing. In my case, most of them start flickering.I'm considering making my own CC LED Driver.The LEDs used are a 12 x 15 mm COB with the markings "MJ304-2 J13". Would anyone know who the manufacturer is? The DR700 is suppose to be a 10.5 Watt LED. I have some of the original driver boards and they appear to source 750mA @ 18V making it more like 13.5 Watts.Connecting the LEDs to a bench power supply, they appear to have a forward voltage of 18V. I can't quite work out the current. With current limiting set at 750mA, one pulls the 750mA. The other pulls 676mA and another 378mA. Hence I'm wondering if the LEDs are faulty, not the drive electronics.Regarding the drive electronics I have found one with a hole blown in D12. You could smell it once you opened the case.(A word of warning, if you disconnect the LED (i.e. the output of the driver is open circuit) you will almost certainly blow the driver up. It appears the two MOSFETs, Q1 & Q3 blow and the output = input)
Calibration Vicious Cycle - Page 1
Forum section: electronics / repair

author: Alley_Cat_Jack
author_rank: Contributor
timestamp: May 14, 2016, 12:57:29 am
content: I recently got a few old oscilloscopes. The one that is functioning needs some calibration. In order to calibrate it, I need a function generator. I don't have a function generator so I was considering building one. If i build one, then I need to calibrate it using a oscilloscope. If I purchase a used function generator, who is to say it will be calibrated? Is there something I am missing? Is there a way I can calibrate my equipment without having to pay big dollars to a calibration center?

author: 10101
author_rank: Contributor
timestamp: May 14, 2016, 01:11:57 am
content: You can build / buy a frequency standard or more than one to calibrate the scope.So just use the key words "frequency standard" on the forum and googleAny other doubts feel free to ask

author: 10101
author_rank: Contributor
timestamp: May 14, 2016, 01:15:11 am
content: https://www.eevblog.com/forum/projects/3-dollar-precision-frequency-standard/?all

author: Alley_Cat_Jack
author_rank: Contributor
timestamp: May 14, 2016, 01:21:52 am
content: Perfect! Thanks guys. You just saved me a lot of headaches. ^.^

author: TheMG
author_rank: Frequent Contributor
timestamp: May 14, 2016, 05:26:20 am
content: In a pinch, you can use a known voltage source (or any voltage source and an accurate multimeter) for amplitude scale calibration. For a rough timebase calibration, generate a tone from a computer sound card, 10kHz for instance. It should be accurate within less than 1Hz, more than good enough for getting an old analog scope in the ballpark anyways.

author: edpalmer42
author_rank: Super Contributor
timestamp: May 14, 2016, 05:53:50 am
content: If you really need to, you can always bootstrap your calibration climb with line frequency. It's more than accurate enough for scope calibration. Use a transformer to drop the voltage to a safe level, then trigger off that. Extend the idea by using a function generator to generate a frequency that's N times greater than line. Use your scope's second channel to display the function generator output and adjust the frequency until the trace stands still. It's limited to low frequency and it can be a bit fiddley, but it'll get you started and it's free!Ed
PSU Repair - Component identification - Page 1
Forum section: electronics / repair

author: bcarm17
author_rank: Newbie
timestamp: May 12, 2016, 12:02:06 pm
content: I can't seem to find the exact part I need. The component in question has the markings S43 P17 on it, three legs on one side and what looks to be a mounting tab on the other side. I would love it if someone could point me in the right direction.

author: Kjelt
author_rank: Super Contributor
timestamp: May 12, 2016, 12:14:30 pm
content: NXP/Philips PBSS4350X ?see datasheet, double check though

author: bcarm17
author_rank: Newbie
timestamp: May 12, 2016, 12:17:01 pm
content: Ok, that's the data sheet I found too but I couldn't figure out what the P17 meant?

author: Kjelt
author_rank: Super Contributor
timestamp: May 12, 2016, 12:24:10 pm
content: That's not specified, could be the batch number for quality tracibility or whatever.Desolder it and measure if it is the specified transistor layout (if it is broken you can test it partly) and if the pcb traces (reverse engineer the schematic) makes sense for this npn transistor, if so order one from some distributor and check if it is about the same.

author: bcarm17
author_rank: Newbie
timestamp: May 12, 2016, 12:31:51 pm
content: Might just order one anyway and throw caution to the wind. From what I've been able to deduce, that component makes sense. But my electronics knowledge is limited at best. Thank you very much for the help. I'll keep you posted about my success or failure at repairing this psu (Thermaltake 875w)

author: TheMG
author_rank: Frequent Contributor
timestamp: May 13, 2016, 01:59:23 am
content: Quote from: bcarm17 on May 12, 2016, 12:31:51 pmHave fun! Just make sure you're wearing safety glasses if you attempt to power up the PSU with the case open. I'm telling you from experience that computer power supplies in general can go off with quite a bang if something isn't quite right. Transistors can end up with big blowholes in them and throw hot shrapnel around.
Scope repair help: B&K (Dynascan) model 1450 Diagnostic Oscilloscope - Page 1
Forum section: electronics / repair

author: atr1_cornell
author_rank: Newbie
timestamp: May 13, 2016, 09:20:30 pm
content: Hi, I have a B&K (Dynascan) model 1450 that needs some help. It has no horizontal sweep, and of course once that is sorted out it will probably show a few other problems, and need to be calibrated.Does anyone happen to have any literature on this? I have looked around quite a bit but found nothing. I would be grateful for a service/repair manual, but anything with a schematic would be great...even a user guide would be a start.Thank you very much in advance.Arthur Russell

author: tautech
author_rank: Super Contributor
timestamp: May 13, 2016, 09:41:18 pm
content: Welcome to the forum.There's every likelihood it belongs to a series of scopes so the 1460 might be very similar. I'll leave this for you to check.http://elektrotanya.com/bk-precision_1460_10mv,10mhz_oscilloscope_sm.pdf/download.htmlWait for "processing" to change to "Get Manual"

author: atr1_cornell
author_rank: Newbie
timestamp: May 14, 2016, 01:16:38 am
content: Thank you! I will check that out.

author: atr1_cornell
author_rank: Newbie
timestamp: May 14, 2016, 01:21:48 am
content: Unfortunately that is a very different model indeed. That is solid state, and is significantly higher performance.My dinosaur here is tubes...eight of them, and I don't see any solid state devices at all. I will check other older models that might be there, but for now I am still very much looking for the info originally requested.Thanks, Arthur

author: atr1_cornell
author_rank: Newbie
timestamp: May 14, 2016, 01:25:43 am
content: Okay, one more post...Here is a link to a place selling that better 1460 for only $30:http://www.ebay.com/itm/like/391454950243?item=391454950243&vectorid=229466&rmvSB=trueSo I think I probably should just recycle this thing. I wanted to fix it just to give it away, but perhaps it really is worthless. Originally it was designed to diagnose analog TV sets...probably (# folks that can do that) * (# folks that need that) ~= 0.-Arthur
Motor run capacitor now has half the expected capacitance - Page 1
Forum section: electronics / repair

author: e100
author_rank: Frequent Contributor
timestamp: May 11, 2016, 01:59:26 pm
content: Had a power cut that affected several houses including mine and it took several hours to be fixed. The repair guys were working in or around the local street transformer but I don't know what went wrong or what repairs were made.Once the power came back on everything in the house started working, except for a single phase induction motor that now just makes humming noises.I pulled the capacitor out and it measures 8uF instead of the 16uF on the label.Is this a typical failure mode for motor caps that have been stressed beyond their rated voltage?Mike

author: dfmischler
author_rank: Frequent Contributor
timestamp: May 11, 2016, 02:13:39 pm
content: Caps fail. Cheap caps fail quicker than good ones. Attributing this failure to any particular event is probably impossible.I have some Reznor UDAP-225 heaters at work that run on 230V (a nonstandard option in the USA). All of the factory motor run caps failed in the first two years. I keep multiples of that cap in stock now because there doesn't seem to be any other choice.

author: wraper
author_rank: Unknown
timestamp: May 11, 2016, 02:17:59 pm
content: It's self healing capacitor. Once the short appears, part of the materialization burns and capacitor still works but with decreased capacitance. Such fault is not uncommon. Motor caps are usually even marked for how many hours they are rated.

author: kleblanc
author_rank: Unknown
timestamp: May 12, 2016, 02:40:49 am
content: Run Caps go very often especially when the equipment is always on. I service HEPA airflow equipment and always have 1 cap (5,7.5,12,15, and a 25 to start locked fans after a decontamination) uF with me. You only notice the problem after power failures or when the equipment gets turned off and the users try to turn them back on.
ZX Spectrum +2 repair - Page 1
Forum section: electronics / repair

author: Shock
author_rank: Super Contributor
timestamp: May 09, 2016, 05:25:19 am
content: Another interesting series, so sharing.

author: voltz
author_rank: Frequent Contributor
timestamp: May 09, 2016, 12:29:11 pm
content: That brought back some memories. Good clear fault finding well explained, quite thorough in his approach.And using his finger twice, once to detect overheating and another to flex the pcb to locate a problem. We should never underestimate our senses (and fingers) for diagnostic use. Expensive IR camera or finger?... both work to some extent.Using a single capacitor to delay the rise/fall time of a logic signal, dirty, but seen that used a lot. I seem to remember the LED display on the old Sinclair MK14 had a mod to increase the brightness of the digits by adding small caps to the segment lines to delay the ON time of the scanned display. Happy days..

author: Shock
author_rank: Super Contributor
timestamp: May 09, 2016, 07:14:13 pm
content: Yeah the workaround was not perfect, I forget exactly where he was at with that specific timing/noise fault but he was probably a day or more in testing to reproduce it and the alternatives had no guarantees for a lot of extra work. It's normally when people throw their hands up in the air and back away so I guess he deserves the kudos for tackling it.His other good series if you haven't seen it can be found here:https://www.eevblog.com/forum/repair/philips-pm3214-oscilloscope-repair/

author: obiwanjacobi
author_rank: Super Contributor
timestamp: May 11, 2016, 07:36:44 am
content: That guy has a lot of other ZX repair videos too. If you like that sort of stuff, it's good info too.I have seen them all
Strange problem? Bad ground? - Page 1
Forum section: electronics / repair

author: biotron345
author_rank: Contributor
timestamp: May 09, 2016, 01:08:03 pm
content: Hi all!I've built a simple LFO for my modular synth based on an LM741. Works well except when I move my hand near it the LFO speed rises very slightly. I assume the is a bad ground? Any advice would be great!

author: voltz
author_rank: Frequent Contributor
timestamp: May 09, 2016, 01:28:39 pm
content: The circuit is such that the impedance at the 741 inputs will be quite high, therefor sensitive to external fields.Without wanting to change the design, i would make sure the Pot case is earthed. Failing that, put the whole thing in a metal box.

author: biotron345
author_rank: Contributor
timestamp: May 09, 2016, 01:33:03 pm
content: Thanks Voltz! Are the any minor changes I could make?

author: voltz
author_rank: Frequent Contributor
timestamp: May 09, 2016, 01:40:09 pm
content: Well, by decreasing both resistor values while increasing the capacitor value to keep the time constant right while at the same time reducing input impedance. But try the earthing first.

author: biotron345
author_rank: Contributor
timestamp: May 09, 2016, 02:39:10 pm
content: Will do, many thanks!!!!

author: biotron345
author_rank: Contributor
timestamp: May 10, 2016, 09:19:45 am
content: Redesigned!!!!
MZC-66 - Page 1
Forum section: electronics / repair

author: Normandr
author_rank: Newbie
timestamp: May 09, 2016, 11:12:42 pm
content: I have an MZC-66 Speakercraft in for repairs. unable to obtain a service manual. all keypads are active except the unit will not turn onunit powers up ok but no action from the keypads , display shows off. any sugestions?Thank You
Plasma Cutter repair and Transistor Question - Page 1
Forum section: electronics / repair

author: edb1984
author_rank: Contributor
timestamp: May 07, 2016, 01:08:28 pm
content: Hello!

author: edb1984
author_rank: Contributor
timestamp: May 07, 2016, 01:29:01 pm
content: Update, also found two other smaller transistors gone.

author: edb1984
author_rank: Contributor
timestamp: May 07, 2016, 01:36:52 pm
content: Photo

author: SeanB
author_rank: Super Contributor
timestamp: May 08, 2016, 01:28:27 pm
content: Likely they are all the same IGBT, though you will not be able to fix the one bottom right back down to the PCB material as the whole pad has been ripped off. Replacing them all, and the 4 driver transistors likely will get this running again. Just check the cremated transistors, they might be a different type than the 2 non cooked ones, you should still be able to see the markings on the char, so see if they are the same or different.

author: EPTech
author_rank: Regular Contributor
timestamp: May 10, 2016, 09:14:21 am
content: Hi there,These modern welders and plasma cutters are actually switch mode supplies that are in constant current mode. The assembly you are showing looks like a H-bridge configuration that switches the primary side of the transformer. The rails marked + and - are coming from the rectified voltage, off the capacitor bank right? The 2 braided wires on the bottom are going to the "big" switch mode transformer, right? In that case you can almost certainly say that all 4 transistors are the same. Be careful though with the polarity of your replacement diodes. They need to be inversely polarized to the current flowing through the H-bridge. They are there to protect the IGBT's from reverse high voltage that occurs at switch-over of the transformer primary.It may be one of the diodes has been shorted, causing a short circuit in the H-bridge. There can only be either one pair of transistors on at any given time. It may also be the IGBT driver is defective, putting an IGBT permanantly ON. As said, I would also swap out the IGBT drivers. They are the IC's connected to the gate, the smaller trace on the transistor, probably via some series resistor. They are probably located on the controller board. Follow the small wires.Good hunting.