hybridfree/eevblog-posts huggingface dataset:
Tek PS2520 (aka GW Instek PPT3615?) repair - Page 1
Forum section: electronics / repair

author: siggi
author_rank: Regular Contributor
timestamp: July 07, 2015, 03:45:04 pm
content: Hey y'all,I'm trying to fix a PS2520 I got for very little money on ePlay. So far I've been through a few distinct failures, and I wonder what the ... expletive ... is up with this thing.The first failure was an 74LS244 shorted across the digital board's 5V rail, which apparently also took out the diode bridge for same - no worries. The second failure was a CD4093 on the CH1 analog board which was near-shorted from 5V to one input. Some of the opto couplers were apparently also getting tired to the point of not making the logic threshold voltages, so I switched all of them out.After I fixed this, I then found that the AD7541 DAC on both CH1/2 was borked, effectively shorting many or all of the logic inputs to the output (and to each other). I only had one of those spare, but now at least one channel is getting near to working - still no output, but I'm seeing likely waveforms and voltages. By first approximation (diode check) the output and driver transistors look OK, so I expect I'll find a bit more logic damage somewhere...This thing has a central digital control & display board whose ground is at mains earth, and then the three output channels are all galvanically isolated with opto-isolators. What I don't get is what sort of event might have caused this carnage across three or four supposedly isolated domains?I'm I looking at a lightning strike victim, or some such?The design of the thing is reasonably interesting - to me at least. There is a serial protocol from the controller to each channel, with a clock and a data signal, plus two distinct strobes. This is clocked into two shift registers, one is 16 bit and goes to the DAC, the other is 8 bits and seems to control readback and maybe relay control.In the reverse direction there's one bit of read-back which is multiplexed to allow reading several different things back (I haven't sorted what's what there). The DAC on each channel is also multiplexed into at least three S&Hs for control voltages (voltage/current and over-voltage cutout), as well as for a software-SAR ADC for read-back.I guess the design dates back to a time where 12bit DACs/ADCs were quite expensive.Now, I'll muddle through, but it'd sure help if anyone has schematics for this thing. Anyone, anyone, Bueller?Siggi
Bluetooth Dainese Jet Stream Tourer - Page 1
Forum section: electronics / repair

author: hbt
author_rank: Contributor
timestamp: July 13, 2015, 05:11:02 pm
content: Hello, all.I own a Dainese Jet Stream Tourer helmet with bluetooth audio and microphone. The helmet worked fine with an old Windows Mobile 6.1 smartphone I had.When I changed to Android, I was never able to make it work out. I'm able to pair the helmet with any Android smartphone, but I can't use the helmet commands to make a call, or even direct the audio from the phone to the helmet.I believe the helmet is not broken in any manner. I believe it has something to do with the Android OS not being able to recognize the helmet and it's protocols, the way it should.I can't get any information regarding the helmet bluetooth module to see if it's A2DP compatible or if some former protocol was used with the helmet.I started to get curious, but got lost on the endless technical information on bluetooth available on the web. I was wondering if someone was willing to show me the best way for me to probe the helmet and the steps to work out a viable solution to make it work out again.The helmet has a small button that used to work to activate the microphone and use the Windows Mobile voice commands to make calls, the button was also used to pick a call or reject it and to control the volume of any audio application running.I'd love to be able to use it again before getting more into depth into a project I have for a HUD projected on the helmet with GPS and rear view cam visualization.Thank you in advance and I hope to hear from anyone soon.Best regards.

author: Shock
author_rank: Super Contributor
timestamp: July 14, 2015, 04:12:03 am
content: Welcome to the forums, I recommend you contact the manufacturer or distributor of the headset and get in touch with someone in their technical support or customer service to help you compatibility or what protocol it uses.Once armed with the headsets technical specs a forum likehttp://forum.xda-developers.com/can help you with Android specific advice and workarounds.Probing might as well be science fiction in this case because in reality you need to know what device your probing, the circuit and how to interpret the signal and protocol. That is after buying the oscilloscope and disassembling while not damaging anything.

author: hbt
author_rank: Contributor
timestamp: July 15, 2015, 02:23:31 am
content: Thank you, Shock.The manufacturer got back to me. Just said it was an old model and couldn't be of more assistance.I didn't remind of XDA. I'll see if anyone may help there.
How old is this SRAM? - Page 1
Forum section: electronics / repair

author: amperium
author_rank: Contributor
timestamp: July 04, 2015, 08:45:03 am
content: Hello,I recently bought an old machine. I saw that there is an SRAM with internal battery in it. Can anyone tell me how old this one is? And how long the battery typically lasts (data sheet: min. 10 years)?Chip:DALLASDS1225Y - 150NONVOLATILVE SRAM0331S 336959PHILIPPINESThanks!

author: dom0
author_rank: Super Contributor
timestamp: July 04, 2015, 08:52:27 am
content: 0331 could mean 2003, calendar week 31.

author: amperium
author_rank: Contributor
timestamp: July 04, 2015, 08:55:22 am
content: Thanks a lot! I definitely should save the data on is!

author: nali
author_rank: Frequent Contributor
timestamp: July 04, 2015, 09:06:59 am
content: Quote from: dom0 on July 04, 2015, 08:52:27 amThat's the format according to the data sheet, the life is from the date of manufacture. I guess the true state of the battery depends a lot on how long the equipment has been powered off.They're still available, not especially cheap though.

author: amperium
author_rank: Contributor
timestamp: July 04, 2015, 09:09:55 am
content: Okay thanks! Costs are not an issue. The man where I bought the machine lost the data once. It cost him about 3000 Euro to get the data and a new chip, because no body cares about this device anymore, its simply too old.

author: justanothercanuck
author_rank: Frequent Contributor
timestamp: July 05, 2015, 02:28:51 am
content: If it really is non-volatile, then it might be possible that the battery is connected to something else. FWIW, Maxim's version of the DS1225Y says data can persist for 10 years unpowered.http://www.maximintegrated.com/en/products/digital/memory-products/DS1225Y.html
Free Laptop / PC Schematics - Page 1
Forum section: electronics / repair

author: Deathwish
author_rank: Unknown
timestamp: July 04, 2015, 04:32:47 pm
content: I dont think this link breaks forum rules. so Go fill your boots as we say in the UKhttp://kythuatphancung.vn/download/http://kythuatphancung.vn/diendan/index.php?/topic/23163-50-asus-laptop-schematics-full-free-download/

author: Fraser
author_rank: Super Contributor
timestamp: July 04, 2015, 05:42:27 pm
content: ThanksAurora
When electrolytic caps go bad, do they usually internally short, or go "open" - Page 1
Forum section: electronics / repair

author: gooseEL34
author_rank: Regular Contributor
timestamp: July 01, 2015, 10:31:01 pm
content: Item is a Polk Audio PSW202 powered subwoofer.Blows 2A fuse immediately.There are 2 4700uF / 35v caps in the power supply. Tops are obviously not blown and spewing goo, but the PCB is covered in black goop (like guitar pedal makers use to coat components and "protect" their design).So. If I cannot see any obvious sign of damage, I "should" be able to set my VOM to resistance and if I touch + and - leads and get a low resistance (40ohm or under) show it bad, right?Can I do that in circuit usually, or do I need to desolder to test it?ThanksTim

author: Flump
author_rank: Frequent Contributor
timestamp: July 02, 2015, 12:21:52 am
content: check the rectifier

author: mrgregs
author_rank: Contributor
timestamp: July 02, 2015, 12:12:34 pm
content: Here is a list of capacitor failure modes with their relative probabilities.Caps should be tested out of circuit and discharged.As for the goop in guitar pedals, it's not usually to protect the designs, but more because if a lead separates, it's always the manufacturer's fault and not the guitarist who stamps on it as if they're trying to push it through the stage, throw it in an already full gig bag from a distance or kick it across a stage whilst it's still connected (or fling it at bandmates and missing), oh no.

author: 0xdeadbeef
author_rank: Super Contributor
timestamp: July 02, 2015, 12:36:24 pm
content: ESR Meters can measure the capacitance and ESR in circuit. E.g. this one here:http://www.peakelec.co.uk/acatalog/jz_esr70.html

author: cncjerry
author_rank: Unknown
timestamp: July 03, 2015, 04:20:19 pm
content: It's probably the output transistors. One of them is shorted.

author: Mephitus
author_rank: Regular Contributor
timestamp: July 03, 2015, 07:08:15 pm
content: Quote from: 0xdeadbeef on July 02, 2015, 12:36:24 pmOr might I recommend building one? I plan to make one soon. Likely something like this:www.eevblog.com/forum/projects/5-transistor-esr-meter-design/msg171364/#msg171364
High Voltage Probe PM 8936/09 is in a bad condition - Page 1
Forum section: electronics / repair

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 02, 2015, 12:46:54 pm
content: Hi,I scored a HV 100:1 probe which is working not optimal.the divider is working so far, but the curve looks as something is to slow.the adjustment with the trim capacistor is impossible, look at the first shot. (the hole for the trimmer is on the small side not visible at my photos)The applied Signal is the 0.5V peak Test Square Generator from my tek 2232.But wait, what if I could adjust it with some of the plenty trimer inside?I do have no clue about the schematics of the probe.Does it make sense to reverse engeneer the schematics or is it useless, because this probe is simply defect and a hobby man like me can not repair it?I thought it could be possible to exchange the defective trim capacistor ...The other turn of the card is what if I have to replace a part, would it be hard to gather?

author: merox
author_rank: Regular Contributor
timestamp: July 02, 2015, 03:18:06 pm
content: I think i have the adjustment procedures for that probe somewhere at my office. It describes perfectly which pot and which cap is responsible for what specific part of the waveform. I think it even has the schematic in it. I'll try to make a scan of it tomorrow.

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 02, 2015, 04:55:06 pm
content: That's awesome!(Danke schön, im voraus )If I could reveive this nice baby I would more than happy.In return I promise I will clean up my Lab and post some PicsI'll don't tell the year ;-)

author: merox
author_rank: Regular Contributor
timestamp: July 03, 2015, 04:18:48 pm
content: Here is the promised manual, unfortunately it's not for the PM8936 but for the PM8931. I don't know what the specific difference between both probes is, but the PCB of both probes seem to be identical so the adjustment procedure should fit to yours.The manual unfortunately doesn't include a schematic, but there is not much inside the probe and on the PCB, so it should be pretty easy to draw down the schematic of it if you really need it.

author: Wh1sper
author_rank: Regular Contributor
timestamp: July 03, 2015, 04:48:22 pm
content: Thanx a lot!I'm trying my luck and will report!Could take a few days because of family restrictions ;-)
HP 6113A repair -- quick note - Page 1
Forum section: electronics / repair

author: TimFox
author_rank: Super Contributor
timestamp: July 03, 2015, 04:46:16 pm
content: I recently obtained an -hp- 6113A 10 V DC precision power supply: a good deal on eBay in "used, untested" condition.The first problem was that the meter had been pushed out of the front panel (possibly in shipment), which broke the flimsy plastic retainer (not repairable). I fixed that with judicious use of Elmer's Stix-All cement, after zeroing the movement.At first, it looked like the supply was working, but out of calibration. After maybe 30 minutes, however, the voltage fell drastically and finally went negative. Sometimes, the supply would re-start with a positive voltage, sometimes not.I traced the problem to VR2, the 9 V zener used for auxiliary bias (including the current limit circuit).Interesting clue: the latest rev on the errata/manual changes list included (Change 13) this cryptic note:"Change zener diode VR2 to 9 V, 0.005% TC, HP Part no. 1902-0785. Note that the old zener diode (1902-0763)should notbe used for replacement at any time."The voltage across VR2 was wrong (roughly 2.5 V); removing it and testing it with a simple voltage supply and resistor indicated that the diode was at fault. Replacing it (on the main board) with a 40-year-old unused 1N936 seems to have fixed the problem.The old diode cross-referenced to 1N2163A, and the new one cross-referenced to 1N936. This is interesting, since the 1N2163A (0.5 W power rating, DO-13 metal hermetic package) looks like it should be more robust than the 1N936 (0.4 W, DO-7 glass package).Try not to disassemble the oven: there are no instructions in the manual and I hope I didn't mess it up too badly looking for VR2. VR1 is inside the oven, along with the precision matched dual transistor Q1 and other parts.
Tektronix 2456B without beam - Page 1
Forum section: electronics / repair

author: Ridgh
author_rank: Newbie
timestamp: July 01, 2015, 10:37:36 am
content: Hello ALL!I need - as far as I know - a major help and assistance:I've bought 2 scopes: 2465A and 2465B. I've tested them prior purchasing for about half an hour and they worked perfect.After a while, on the 2465B, I've observed that the trace and readout are dimming after approx. half hour up to disappearing completely. I found a friend that told me to change the capacitors on PSU and I did it.The new capacitors are on specs, but maybe it was mentioned on this forum that 2 capacitors are interchanged on Layout. After this "incident", I got no trace or readout.The 'scope does several tests (the 4 channels are tested, and at "ADD" it remains stuck). After pressing A/B Trig, the panel lamps are working and responding, there are "clicks" when they should be (compared to the A version, but nothing appears on CRT.Just after several hours it is disconnected (5-24 hours), the beam appeared, without readout.I understood that A5 PCB has a problem, and indeed I've found several leakages from electrolytic caps. There was a lot of "salt" on the solder, and as well a 10k resistor (0.1%) burnt. I exchanged them with what I had on my lab and ordered new ones that are supposed to arrive within 2-3 days. All the voltages at J119 are as specified on the service manual. The DAC shows me that I have inputs as they should be, the microprocessor pin 40 is high (it should be), and I have a good stable clock at pin 39. The DAC has normal measurements at pin 16 and 19.The U800 is not too hot (approx. 50*C after 20 minutes).These are the details so far. From time to time, (long time...) the 'scope gets a beam, but it surf down the screen up to ~70%. It can be moved up or down, right and left. However, if I turn it offeven for a second, I can see nothing again on screen.The recall button works, I can recall the saved configurations. The beam finder doesn't work.I'll be more than thankful if any of the members from this forum may help or get an idea for what I am supposed to look for further.This is the summary, and I have no idea what to do further...Thanks in advance,Ridgh

author: poot36
author_rank: Frequent Contributor
timestamp: July 03, 2015, 12:29:02 am
content: I would try reseating all of the connectors in the scope and check that you are getting the proper voltages to the crt. It could be the blanking circuit is not working correctly and is always blanking the screen.
Sony - KDL-32EX400 trouble shooting no turn on - Page 1
Forum section: electronics / repair

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 09:34:01 pm
content: I am trying to figure this out. My brother in law said he thinks it was a power surge from a storm that got it.I have been trying to test the boards but when i looked this one up in Google I found a place that said it was the main board.Here is my dilemma... I think it is the power supply because the ONLY voltage coming over to the main board is 3.3v and that is on 2 leads only ALL the rest are 0000v.... (photos attached)Now I could assume the main board sends voltage signal back to the power supply to trip mosfet and relays..But I just think it is a bad power supply because the 12v raid is not live on the cable as well as it seems odd for it to function in the way described.So time to ask the experts... trying to learn more so Thanks in advance.Doc

author: poot36
author_rank: Frequent Contributor
timestamp: June 28, 2015, 08:57:43 pm
content: Most TVs have a low voltage standby line from the power supply to monitor the remote control and the power button. When the TV detects that you have turned it on it will send that low voltage back to another pin on the power supply instructing it to turn on the rest of the outputs. Check that the power switch is getting power and if it is not then the main board does have a fault on it. Try to find the service manual for the TV as it sometimes will have various tests that you can preform to check that the main board is the problem.

author: silviustro
author_rank: Contributor
timestamp: July 01, 2015, 12:20:04 am
content: As poot36 said, most TVs have a 3.3V standby power line going to the main board. Once it receives the command to turn ON, it signals the power supply to switch the 12V and 5V lines ON as well. There might be something wrong with the main board not signaling the power supply to switch the voltage lines ON.I know this is basic stuff, but if it was a power surge, check the fuses.... always check the fuses.

author: mzacharias
author_rank: Frequent Contributor
timestamp: July 02, 2015, 11:31:37 am
content: You should have a turn-on (Power-On?) line from the main board back to the power supply. Monitor this line while the power button is pressed. Should change states, High to Low or vice-versa.First of course, check fuses and any other fusible devices on the power supply board.A shortcut might be to see if there is any DC voltage on any pins of the remote sensor. If not - high likelihood of the main board being bad.
Removing ECC from Ram - Page 1
Forum section: electronics / repair

author: leham
author_rank: Regular Contributor
timestamp: July 01, 2015, 05:37:02 am
content: just a thought..I have some DDR3 ECC sticks of RAM here and was wondering how one could make them non ECC and operate like standard memory?The main difference visibly on the PCB I can see between ECC and non ECC is one large IC usually in the middle of the pcb. On the RAM I have here it's part number isinsste32882lv-gs02DDR3(L) - Registering Clock Driver with Parity CheckingIf I where to just desolder that part what do you think would happen?I have a feeling nothing ....

author: Psi
author_rank: Super Contributor
timestamp: July 01, 2015, 06:06:04 am
content: Have you tried it as is?Some BIOS's support it but don't tell you in the manual

author: leham
author_rank: Regular Contributor
timestamp: July 01, 2015, 06:30:59 am
content: yes I have and it did not work :C

author: oPossum
author_rank: Super Contributor
timestamp: July 01, 2015, 06:36:43 am
content: Seems like you have registered EEC RAM typically used in servers, and the system you want to use it in requires ordinary non-registered RAM. Having the extra bits for ECC usually isn't a problem - they are just ignored by systems that don't support ECC. The incompatibility is due to it being registered. Removing the chips won't magically fix that.

author: amyk
author_rank: Super Contributor
timestamp: July 01, 2015, 12:59:38 pm
content: You could try removing the register and then bridging the appropriate balls to convert it into a non-registered DIMM. The SPD EEPROM would probably need its contents modified too.That particular part has no datasheet I can find, but it looks like a "32882" is a standard DDR3 clock driver+register with a common pinout.Here is a detailed datasheet.Look up the JEDEC standards (they're freely available) for more information.http://www.jedec.org/standards-documents/results/taxonomy%3A2827http://www.jedec.org/standards-documents/docs/jesd82-29ahttp://www.jedec.org/standards-documents/focus/memory-module-designs-dimms/DDR3/240-pin%20Registered%20DIMMs

author: TiN
author_rank: Super Contributor
timestamp: July 01, 2015, 03:18:35 pm
content: As already mentioned before, using ECCunbufferedDIMM is straight-forward, extra byte for ECC will be simply ignored if not supported by platform.You can visually identify ECC UDIMM by it's look, it will just have extra DRAM chip for ECC byte, making up for 72 bit databus (64+8), while usual DIMM have 8 or 16 chips (8*8 = 64 bit databus).Registered or buffered DIMM is whole another story, as it's addressing/command topology is different.You can see in example diagram from internets here:And in your case, you have ECC RDIMM, which cannot work in usual platform. There are some exceptions, for example most PC motherboards on Intel X79 and Intel X99 platform (LGA2011 socket), which can support RDIMMs if Xeon CPU is installed, but that's because this platform is natively goes from server design.
Megmeet MIP329FL LCD TV PSU - Page 1
Forum section: electronics / repair

author: Signal Simon
author_rank: Contributor
timestamp: June 29, 2015, 10:13:27 pm
content: Hi,I'm after some service info on the Megmeet MIP329FL PSU/inverter. Google hasn't returned anything useful.It's fitted in an el-cheapo "Cello" brand LCD TV with CCFL backlighting, but the PSU seems to be far better design and build quality than the norm for LCD TVs.The backlight has failed but the signal processing side of the TV itself works fine.The picture can be seen on the screen if a light is shone on to it.There issomeoutput from the inverter, but not sufficient to strike up the lamps.Can anyone help?Thanks,Simon.

author: lpc32
author_rank: Frequent Contributor
timestamp: June 30, 2015, 01:23:10 am
content: Maybe it's similar enough to some of their other models?http://www.google.com/search?q=site:badcaps.net+megmeet

author: Signal Simon
author_rank: Contributor
timestamp: July 01, 2015, 01:45:16 pm
content: I had a look, couldn't get any schematic or useful info on how it works.Somebody was saying the transformer is faulty, but I would have expected some fireworks if that was the case.The transformer does get slightly warm - not as much as you'd expect in normal use though.I might bring the set back home to investigate on the bench.I do have an isolating transformer so can play safe testing primary side - the inverter runs off the main 400V and has transformer-isolated gate drive, not like the 24V inverters that most use.
Potential problems with chipped resistor insulation? - Page 1
Forum section: electronics / repair

author: lpc32
author_rank: Frequent Contributor
timestamp: June 30, 2015, 01:15:52 am
content: What sort of problems can be caused by chipped insulation on an axial resistor? I'm not seeing a problem, but I wonder.

author: flynwill
author_rank: Regular Contributor
timestamp: June 30, 2015, 03:05:10 pm
content: If it is only chipped insulation the answer is probably "none". If the ceramic body has been cracked by whatever blow caused the insulation to crack then the part may already be a higher resistance than it should be and may fail totally at a later date.If the part is easy to replace then I'd recommend just replacing it. If that's difficult then I'd examine it carefully under good magnification to try to determine the extent of the damage.

author: lpc32
author_rank: Frequent Contributor
timestamp: June 30, 2015, 11:46:09 pm
content: It was chipped when I removed a nearby jumper that was glued/epoxied also to the resistor. It's difficult to see if the resistor core is exposed or not, and difficult to access.But just as a general question, what's the function of the insulation? Prevent accidental shorts, arcing, protect core deteriorating from environment?

author: German_EE
author_rank: Super Contributor
timestamp: July 01, 2015, 10:31:17 am
content: Just dab some nail polish on the broken component.

author: amyk
author_rank: Super Contributor
timestamp: July 01, 2015, 01:00:13 pm
content: Check its value, if it's out of tolerance then replace it.
Need datasheet Motorola 352 SBS8 - Page 1
Forum section: electronics / repair

author: DarrylP796
author_rank: Newbie
timestamp: June 28, 2015, 04:10:00 pm
content: Hi everyone,I'm working on an older piece of electronics from around 1985. Am in need of a datasheet for what looks to be a transistor, but that in the circuit has no connection to the "base" lead. Had never seen that before. It has three terminal leads, just no connection on what would be the base. Markings are Motorola insignia and 352, then SBS8 on the next line. TO-92 style case.This device is being used as part of an input circuit to a 4N35 opto-isolator. 120V AC goes through a divider and single diode rectifier, approximately 10VDC pulses (no smoothing on rectified AC signal) then goes through this mystery device and then into the opto-isolator pin 1. Maybe this is a common transistor being used as a "negistor" just to get the voltage drop, making sure only "peaks" of the rectified signal pass to the opto-isolator? Tests out like a common PNP transistor in circuit using my DVM. Just no base connection on the board. The intent of the output of the opto-isolator is to make sure the 120VAC is present in the system on the output of a control relay. That's what the circuit is designed to be making sure of.Any help is welcome.The transistor is labeled with the Motorola logo and then the number 352. Just below that is "SBS8".Anyone have a datasheet on such a beast? I can't find it online with all the normal searches.

author: Fank1
author_rank: Regular Contributor
timestamp: June 30, 2015, 08:53:53 pm
content: Try Google "DIAC"
Biccotest T435M repair advice - FIXED - Page 1
Forum section: electronics / repair

author: Signal Simon
author_rank: Contributor
timestamp: December 20, 2013, 09:35:34 pm
content: It's a Cable Fault Locator - aka TDR. It's a CRO based unit with 7-segment LED fault location readout. It's about 1980 vintage.I was given this by a previous employer in about 1995 as their usual calibration and repair house returned it as "Beyond Economic Repair".There was no X deflection.So what did it cost to get some life out of it?...Well I bought a service manual from the manufacturer and soon determined the faulty component.... a CMOS 4069UBE IC for the trace gating!£60 for the service manual and a few pence for the 4069!However I did find that the Y-Amp was extremely sensitive to humidity.I replaced the MPSA42 and MPSA92 deflection transistors at the time - there were some signs of metal migration into the transistor cases.Within a few months of that repair I did use it to successfully locate 3 cable faults, but had many problems with the Y-deflection going off the screen.I've kept the instrument and the original service manual and I want to get this back into a useable condition.Any tips regarding the extreme moisture sensitivity - even breathing near the uncased unit on the bench would send the trace up and off the screen!What's it best to clean off conformal coating with? And is the Elelectrolube APL compatible with the older stuff?Thanks,Simon.

author: Signal Simon
author_rank: Contributor
timestamp: June 29, 2015, 09:59:09 pm
content: Ok well I decided to blow the cobwebs off this one and have another go.On closer inspection, only a small area of the board is conformally coated - the CRT HV tripler area.It wasn't that obvious, but there were signs of leakage from the "Mempac" 3.6V NiCd battery - and with the instrument being stored vertically this leakage had headed towards the deflection amplifiers.After desoldering numerous components, I gave the PCB a good scrub with flux remover as I had found it to be very good at restoring battery contacts after leakage.Reassembled and.... SUCCESS!There is still a barely-perceptible decrease in X-deflection when breathing on the PCB, but no change whatsoever to the Y-deflection in either amplitude or shift.I'm calling that one sorted.The Mempac battery will not be getting replaced - I have no need to store a trace after the instrument is powered down.Simon.
If only all faults were this easy to diagnose - Page 1
Forum section: electronics / repair

author: KJDS
author_rank: Super Contributor
timestamp: June 27, 2015, 07:49:12 pm
content: All I need now is to work out what I'll replace the blown resistors with.

author: Deathwish
author_rank: Unknown
timestamp: June 27, 2015, 08:12:52 pm
content: https://ia801700.us.archive.org/32/items/FarnellLfm3TestOscillatorManual/FarnellLfm3TestOscillator.pdf

author: SeanB
author_rank: Super Contributor
timestamp: June 27, 2015, 08:16:58 pm
content: At least you can still read the exact value, though that 100R resistor on the left has definitely escaped the visual QC check with that coating defect.Looks like they were input terminating resistors, and very precise at that.
Ez Dm-441b service manual  - Page 1
Forum section: electronics / repair

author: fivefish
author_rank: Frequent Contributor
timestamp: July 02, 2015, 07:01:01 am
content: I'm trying to calibrate this multimeter . Does anyone have service manual for this? Thanks.

author: Deathwish
author_rank: Unknown
timestamp: July 04, 2015, 05:22:27 pm
content: http://elektrotanya.com/dm_441b_tisch_multimeter.pdf/download.html

author: Hydrawerk
author_rank: Super Contributor
timestamp: July 04, 2015, 05:42:40 pm
content: This DM-441B was manufactured under brands GoldStar, LG Precision and EZ Digital. It must be a 1995 or older design.

author: fivefish
author_rank: Frequent Contributor
timestamp: July 04, 2015, 07:10:21 pm
content: That electrotanya site is Total crap. Tried several times to register and after successfully being registered, it just keeps going around in circles. Never seen a site that intentionally discourages people to use it, and very difficult to use.If I can find this manual on eBay, I would have bought it already.

author: miguelvp
author_rank: Super Contributor
timestamp: July 04, 2015, 08:26:14 pm
content: Try this link, slow site but I did download the pdf with no problem:http://www2.produktinfo.conrad.de/datenblaetter/100000-124999/120901-sp-01-en-DM_441_B_Tisch_Multimeter_Kalibrier.pdfDon't worry, the manual is not in German, it's in English.

author: Deathwish
author_rank: Unknown
timestamp: July 04, 2015, 09:04:38 pm
content: I never login and am not a member, I merely click the link under the picture that says document previewThis file is downloadable free of charge: Get Manual, and download it, it does take a second or two to process the get manual link but thats it.

author: fivefish
author_rank: Frequent Contributor
timestamp: July 05, 2015, 03:39:50 pm
content: Thank you miguel! Very helpful. I appreciate it very much.

author: miguelvp
author_rank: Super Contributor
timestamp: July 05, 2015, 03:50:18 pm
content: I did try Deathwish link and if you had just clicked on "Get Manual" it would have worked without signin required.But I get it, those websites for downloads usually have a ton of download buttons to get you to click on advertisers, The one he linked is not as bad as others though.Edit: even if it's the same doc, I would still get his, because it seemed it was a better quality scan, but didn't look too much in detail so might be the same thing. Still worth your while to get both just in case.
HP ESG1000A Repair - Page 1
Forum section: electronics / repair

author: wavebits
author_rank: Contributor
timestamp: June 25, 2015, 09:46:39 pm
content: I am trying to fix my ESG1000A signal generator and need some advice. The unit had two problems. Missing RF output between 250-500 MHz and error 605. I was able to repair the missing frequency range by replacing a bad divide by 2 NEC scaler chip on the synthesizer module. It now has RF from 250K to 1GHz.The error "605 DSP FW Download Failed" has proven to be more illusive. The error occurs at boot-up and anytime a change is made to the modulation settings. If FM modulation is turned off and back on, or the modulation frequency or depth is changed, the error clears then re-appears. The micro must be trying to send data to the DSP chip to set it up, but is failing to do so. No modulation is therefore possible. External modulation works fine with an audio signal applied to the EXT-1 input. The DSP provides a very nice function generator for modulation with multiple waveforms including dual sine with independent frequency and amplitude levels.The documentation is sparse on this unit. The error message is explained in the manual as If this happens "contact HP" No schematics are available to mere mortals for the ESG series.Has anyone ran into this problem and offer any troubleshooting tips? All supply voltages are present and WNL. The DSP appears to have some external RAM connected to it. I don't know if the main FW is corrupted and sending bad data to the DSP or there is a hardware problem between the main processor and the DSP or possibly the DSP RAM is bad. Other than the DSP related functions, the RF portion is working normally with proper output levels over the attenuator ranges. No other errors appear in the queue.Thanks, Dave K7DMK

author: wavebits
author_rank: Contributor
timestamp: June 26, 2015, 05:22:22 am
content: I did a little more troubleshooting tonight. Looking at the ADSP-2101 DSP chip with a scope showed no activity on the data or address lines. VDD was OK at 5.1V Checking the clock output pin showed no clock. Probing the crystal revealed the xtal was not oscillating! I temporarily bridged a junk box 14 MHz crystal across the old one while looking at the clock pin and bang, a nice clock pulse. Digging deeper in the junk box I fould a old Ziatech CPU board with a proper 16 MHz crystal. All is well.So a bad DSP clock crystal was the problem. This was a free standing crystal, not an oscilator module. I have personally not seen many failed crystals in the past.Dave, K7DMK
SOLVED - Rookie knot - samsung ln40a450c1d inverter to power supply - Page 1
Forum section: electronics / repair

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 01:48:43 am
content: I did a dumb thing.I disconnected the cables from my power supply before I took photos of the same. Now after waiting 3 weeks for the mosfets to come i got them installed but being still a newbe I do not know which lead to connect from the inverter to the power supply. One is white and one is pink. they are separate connectors each to the end of a coil/transformer.I can usually tell by the length of the wire or the memory of the bend but these are exactly the same. I will attach photos of both boards...It may not matter but i do not know...Thanks for a rookie bail-out....The last photo is my guess but i was hoping for someone who knows to assist please.

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 03:29:10 am
content: Found the answer purely by accident or was it???Google search led to Ebay for replacxment board, guy had photo with wires on it still...NICE!!For the next poor mistake riddled guy like me.... WHITE on top connector, PINK (or blue) on the bottom one.Turns out my guess was correct had a 50/50 after all...Thanks anyway.. was a tough one at best.

author: Riotpack
author_rank: Regular Contributor
timestamp: June 26, 2015, 03:37:23 am
content: http://elektrotanya.com/samsung_ln26a450c1d_ln40a450c1d_chassis_n45a.pdf/download.html

author: Doc38343
author_rank: Contributor
timestamp: June 26, 2015, 04:02:16 am
content: Quote from: Riotpack on June 26, 2015, 03:37:23 amTiny bit late but NICE Thanks! I will save the site for future reference, much appreciated!Photos confirm correct placement and another successful board repair 2 fried FCPF11N60 mosfets and 1 470uF 35v cap as opposed to just a $129 board swap out... I Love It!!! nothing is better except... well uh we won't go there!
GenRad 1455-A K-V Divider Replacement Case? - Page 1
Forum section: electronics / repair

author: eas
author_rank: Frequent Contributor
timestamp: June 25, 2015, 12:57:03 am
content: I bought parts for a GenRad 1455-A 4-decade K-V Divider from a guy on Ebay who extracted it from an old piece of vibration testing equipment.All the crucial bits are there, the 4 low-resistance rotary switches, the precision-wire-wound resistors, the GenRad knobs and front plate. In fact, it looks like the people making the "sensitivity computer" it was pulled from just got a unit from GenRad, removed the case and mounted it in their instrument chassis with some extension shafts on the knobs, and wired it up. Not bad for $29 + shipping.Now though, I want to find a replacement case for it. The front plate is ~ 3.5"x14.75" and the guts extend a bit less than 3.75" from the back of the front plate. The back of the front plate has threaded studs set in about 1/4 inch from the edges. From photos of other GenRad gear of similar vintage it looks like these are attached to brass standoffs and then the bottom is held on by screws through the bottom into the standoffs.I'm hoping I can find a metal suitable housing for ~$30 or so that doesn't require more than some holes drilled, and maybe some paint. I looked at Hammond, but didn't find anything as big, at least not in their die-cast enclosures or instrument boxes.Any ideas/suggestions?If anyone else is interested, the sellerhas one more. When I first hooked mine up to test I had some problems at the top and bottom of the first decade, which I think were due to a couple of the resistors having their leads bent so they shorted. Once I fixed that, everything seems good. I haven't gone through in great detail, but things seemed accurate to at least 0.01% or better. I'll have to do a more careful study to see if it hits its original specs, but its at least as good do buying a set of precision resistors and switches for a lower price and a lot less hassle. The only other issue is that the dials are the wrong color for the original faceplate. I'll have to see if there are replacements available, that, or just cut something to put behind them to get the necessary contrast.

author: Vgkid
author_rank: Super Contributor
timestamp: June 25, 2015, 02:01:23 am
content: Make a case out if wood, and line it with copper sheet.

author: eas
author_rank: Frequent Contributor
timestamp: June 25, 2015, 03:10:40 am
content: I may well end up doing that, but my first choice would be a sturdy, ready-made metal chassis that just requires drilling a few holes.
Component Identification - SOT23-5 "162Z" Voltage Regulator (?) - Page 1
Forum section: electronics / repair

author: bookaboo
author_rank: Frequent Contributor
timestamp: June 24, 2015, 12:13:13 pm
content: Hi,I've got a remote control for repair, a SOT23-5 component has been physically broken off the PCB and the pins damaged beyond repair. Under the microscope I can see the markings "162Z". I've been googling for ages but I can find no reference for this marking code.Tracing the circuit I'm fairly sure its a voltage regulator feeding a MSP430F149. I could just whack in any old 3.3V regulator and see but I'd like to know the specific voltage and type of this regulator.Does anyone have any ideas ?

author: amyk
author_rank: Super Contributor
timestamp: June 24, 2015, 01:39:23 pm
content: Likely to be aG916T1UF(datasheet here)If the surrounding circuitry contains an inductor, it might beR1223N332Abuck regulator.
Help: HP4274A process amplifier DC offset adjustment - Page 1
Forum section: electronics / repair

author: nctnico
author_rank: Super Contributor
timestamp: June 23, 2015, 01:04:19 pm
content: I recently acquired a HP4274A and I'm having some trouble with one of the adjustment procedures: section 5-20 process amplifier DC offset adjustment. I downloaded the service manual from Keysight's website but unfortunately the scope images are unreadable and the text is not very clear (probably translated from Japanese). Does anyone know/have a better source for this adjustment procedure? Maybe a color scan from an original manual?
Panasonic TX-P42GT30B  Defective - Page 1
Forum section: electronics / repair

author: eyesociety
author_rank: Newbie
timestamp: June 22, 2015, 09:29:59 pm
content: Hi all,Just got hold of a panasonic TV Model TX-P42GT30B that has 8 blinks of the led.Found that the TNPA5330 board is defective, so I am after a service manual, had a look at this sitehttp://www.schematicsunlimited.com/but had no luckJust don't want to throw it into the skip.So I am wishing that some one on here will point me in the right direction.Thanks.
A cheeky question - anyone got a couple of 74AC251's spare - Page 1
Forum section: electronics / repair

author: gerrysweeney
author_rank: Regular Contributor
timestamp: June 22, 2015, 08:47:43 pm
content: Hi,I need to make a quick repair and need a couple of 74AC251 SOIC package. I can buy from Farnell, Mouser etc no problem but postage is £12 and I cant really wait for my next batch order from there. If anyone in the UK has a couple that would be willing to sell to me that you could pop in the normal post, or if you are near by I could even collect that would be most helpful. Hope no one is offended by the question.Gerry

author: gerrysweeney
author_rank: Regular Contributor
timestamp: June 22, 2015, 09:24:47 pm
content: Don't worry, I just found RS components here in the UK will do free next day postage on a small order of 10 pcs costing only £2.60 + VAT - thats pretty awesome considering what Farnell and Mouser charge. +1 for RS - ordered and all sorted.Gerry
6177C decent scan of schematic? - Page 1
Forum section: electronics / repair

author: motocoder
author_rank: Unknown
timestamp: June 22, 2015, 02:56:01 am
content: I'm off on another repair, this time an HP 6177C. Keysight has a scan of the manual, including a schematic, but the quality of the scan is so poor that I'm having trouble reading the numbers. Does anyone know of a better quality scan of this manual, or perhaps have access to a paper copy that they could scan for me?Thanks

author: motocoder
author_rank: Unknown
timestamp: June 22, 2015, 04:54:43 am
content: Found one here (one of the links in the sticky thread):http://exodus.poly.edu/~kurt/manuals/manuals/HP%20Agilent/HP%206177C,%2081C%20Operating%20&%20Service.pdf

author: motocoder
author_rank: Unknown
timestamp: June 22, 2015, 05:19:55 am
content: The pages were upside down in the higher res PDF. I've fixed this using a trial copy of Adobe Acrobat, but I don't know how to reach the owner of that site to get him to update the copy. If any knows how to reach the owner of that site, please reply to the thread. Otherwise, if someone else is willing to host the corrected PDF, I can provide it (it's ~3MB - too big to upload as an attachment here).

author: johnh
author_rank: Regular Contributor
timestamp: June 22, 2015, 07:59:50 am
content: http://www.ko4bb.com/cgi-bin/upload.pl

author: motocoder
author_rank: Unknown
timestamp: June 22, 2015, 01:33:40 pm
content: Quote from: johnh on June 22, 2015, 07:59:50 amThanks. I *think* I uploaded it, although it happened so quickly I wonder if it didn't actually upload correctly.Also, for those that want an even better quality scan, I found a vendor that sells very good quality scans for $10. I got his scan of the 6177C/6181C manual, and I am very happy with it. The schematic page in particular is 10 times better than the poor quality scan up on the HP/Agilent/Keysight web site. I'm not affiliated with this guy at all, just passing on the info.http://artekmanuals.com/
NAD 118 service manual - Page 1
Forum section: electronics / repair

author: meeder
author_rank: Regular Contributor
timestamp: March 26, 2015, 10:28:31 pm
content: I have been looking for the service manual for my NAD 118 digital pre-amplifier. There are some dubious websites which claim to have it but I was never able to download it.NAD Electronics isn't helpful, they only say that I have to send the unit in if it needs repair which I will never do because of the age of the unit. It is a real rare beast and they have not sold many of these units during the brief period it was available.So is there anyone here who could help me to this service manual?

author: cdev
author_rank: Super Contributor
timestamp: March 28, 2015, 03:10:38 am
content: I have an old NAD receiver which I love, and I was looking for the service manual for a long time. But I finally found the manual.I would check electrotanya.com. I am pretty sure they have a bunch of NAD service manuals there.

author: meeder
author_rank: Regular Contributor
timestamp: June 22, 2015, 11:26:32 am
content: They seem to have died. Electrotanya.com is now a placeholder for the domain.I did however get the schematics from someone on this forum so that is a good start.I am not 100% sure if there even is a true service manual available since the NAD 118 didn't live that long as far as I know. It was introduced in the mid 1990's and it had quite a high price to my knowledge.
Good Will GFG-8020G Funcion Generator Transistors - Page 1
Forum section: electronics / repair

author: Dwommynator
author_rank: Newbie
timestamp: June 25, 2015, 12:31:35 pm
content: Hello I'm new to the Forum.I have a question about a function generator I recently bought from somebody.It's about aGood Will Instruments GFG-8020G.I need new transistors (TO-39 Package) forQ506andQ507and have no clue which types I need, because there was paint or goo on them.When I tried to scrape it off I managed to also scrape the numbers and letters off.The only thing left visible, was on TransistorQ506that has the MotorolaMand under that the first two Letters2N...with direct under that the first two lettersK8....On TransistorQ507I could barely see something that looks like the letterKon the bottom line.I hope there is somebody who can help.Included a Picture.Thanks

author: mij59
author_rank: Frequent Contributor
timestamp: June 25, 2015, 02:03:29 pm
content: Checked my GFG 8015G, layout is different but the transistors with heatsink are 2N2219A and 2N2905A

author: Dwommynator
author_rank: Newbie
timestamp: June 27, 2015, 10:44:08 am
content: Ah Great!Thanks for the quick help.Yes GFG 8015G might use the same transistors, I think?Anyhow,Thnx again
advantest r3131a master oscilator calibration - Page 1
Forum section: electronics / repair

author: cncjerry
author_rank: Unknown
timestamp: July 08, 2015, 06:30:35 am
content: I have had the subject spectrum analyzer for a year, works well, came with the tracking generator, but my WWV testing confirms the master oscillator is off 180hz at 10Mhz. I've tested it against other sources as well. I isolated the WWV carrier with a crystal filter then measured it with the analyzer's counter. I also brought the resulting signal out using the tracking generator while the unit wasn't triggered and measured it with a known counter. In both cases the delta was 182hz. I have a way to feed it an accurate 10Mhz signal in the back, so I can get around the problem, but it annoys me. I also used an A/B function in a Tektronix counter and that gave me the same delta. The offset is less as the measured signal drops.I tried pulling it apart, was able to get the back cover off, but there must be a trick to disassembling it further. I thought if I got it apart I would find the 30Mhz master oscillator and give it a tweak but can't even get that far. Sounds like I must be pretty lame but I can assure you I am good at puzzles. Taking the back cover off just exposes a ton of sheet metal; the front bezel comes right off but there I am stuck. It seems like the wrap-around casing should slide off the front maybe but it won't budge.Anyway, if someone has experiences with this unit, please pass along the secret.Thanks.Jerry

author: HighVoltage
author_rank: Super Contributor
timestamp: July 10, 2015, 10:08:58 am
content: Send a request for a service manual to Advantest Japan.They usually respond right away within a day or so and attach the manual or send a link to it.