hybridfree/eevblog-posts huggingface dataset:
Solartron Schlumberger 7150plus:replacing power filter and some pimping - Page 1
Forum section: electronics / repair

author: Zermalmer
author_rank: Regular Contributor
timestamp: July 21, 2018, 06:27:03 pm
content: Hi,I bought a 7150plus and had the hope, that I can avoid the repacement of the power supply filter.But I was wrongFirst short test after arrival was ok.Then I took it to the lab and let the 7150plus warm up...20 to 30 minutes later I reentered the lab and the device send small clouds of dying.But I had a little bit luck, because only a small amount of "the sauce" left the filter, so the cleanup (beside the smell) was not so big.So I had to replace the filter (damn...the price still hurts)Based on all the 7150 and 7150plus threads I also decided to pimp it a little bit and also wanted to replace the backlight and the plugs.And also I wanted to be prepared to be able to calibrate the device.So I build also a cal-jack-plug, and yes as right detectedin this threadit is a 2,5mm jack.Instead of other threads and posts in the internet I decided to use the Stäubli SLB4-E plugs. (not gold plated)And I also exchanged the plugs on the backside.For that I had to file away a little bit of the isolation of the Guard-plug, so that it fits over the resistor. (Let me know if you want to see a pic, then I will make one...totally forgot to make one)I think the printings of the backside are still good readable.From another older project I had left some 5mm amber LEDs and put them in.The color of the light seemes to be identical to the original, but only brighter.Best regardsAndreas

author: DC1MC
author_rank: Super Contributor
timestamp: July 21, 2018, 07:34:26 pm
content: Congratulations Andreas, it looks very, but I still like my white leds, the calibration plugs on the other side, have no competition, absolutely perfect.I'm hunting for 7150+ or a 7151, if someone has a 7151, I can offer one of the 7150 & difference.So far the Kleinanzeigen only produced a Solartron "Cunter" with nice Nixie tubes.https://www.ebay-kleinanzeigen.de/s-anzeige/solartron-frequency-cunter-em-1616/835104668-168-16814Cheers,DC1MC

author: Zermalmer
author_rank: Regular Contributor
timestamp: July 21, 2018, 07:49:57 pm
content: Thanks DC1MC.I only had 2 white LEDs left from another project... so the amber wonOn ebay-Kleinanzeigen was a 2nd 7150+ after I bought this one ~3 weeks ago.But the second one cost 100Euro more than I have paid (from the same seller)...but it looks like he sold it anyway.I think there was also a 7151 in the past, but that was 5 to 7 weeks ago (or was it ebay? and the price ended in a region that was not worth it to me.Best regards.Andreas

author: DC1MC
author_rank: Super Contributor
timestamp: July 21, 2018, 07:58:42 pm
content: My Fleabay properties (Klein- und Groß- Anzeigen) search-fu lately produced just a 7150 that was sold as a 7150+ (seller corrected and sold it a bit later) and a lot of strange pressure sensors and strain gauge amplifiers.And some 12xx unicorns, way too unaffordable for me.If you see some and want to share them, drop me a line.Cheers,DC1MC
THS720A Tektronix Scope Power fail - Page 1
Forum section: electronics / repair

author: TekTHS720A
author_rank: Newbie
timestamp: July 10, 2018, 11:21:07 pm
content: Have had THS720A scope since new and it has worked without incident until recently. Believe a portion of the power supply has been compromised but please give other opinions. Some details: Power from 110VAC charger is 14VDC, voltage at NiCad battery terminal is 12VDC. Battery was in poor condition and I'd operated the scope without the battery installed using only the power supply. Channel 1 shows no response but appears on screen as open channel, Channel 2 shows waveform but voltage magnitude is wrong--too low in amplitude. Frequency and scaling (both axes) is correct and can be changed with associated switches. A 9VDC battery attached to DMM terminals returns 4.5VDC when this mode is activated. Battery voltage was confirmed using a separate handheld meter. Tested scope probes on another instrument without issue.There are 4 electrolytic caps mounted in main board power supply region. Have not replaced these but there is no evidence of deformation or leakage. No components appear damaged and no evidence or arc tracks. Was using scope on 10VDC signal, channel 1 only when failure occurred.Don't quite understand how this power system should work. Voltage to battery seems very high and shouldn't a negative supply be generated? Thanks in advance for your thoughts on troubleshooting.

author: HighVoltage
author_rank: Super Contributor
timestamp: July 11, 2018, 11:37:39 am
content: May be the PCB is contaminated from a leaking battery?How bright is the LCD?Follow the power rails and see if it drops somewhere.

author: TekTHS720A
author_rank: Newbie
timestamp: July 12, 2018, 02:07:33 am
content: No battery leakage. Can't see any cracks on PWB either. Going to start probing Vcc's on nearest neighbor IC's. I've seen related posts about screen illumination but I've not had the problem--my screen is bright, remarkably easy to read. Thanks.

author: z01z
author_rank: Regular Contributor
timestamp: July 12, 2018, 06:37:51 am
content: The schematic diagram is available, as well as the component BOM. Google for THS7XXAPDiag.pdf and THS700_Supplement.pdf.There's more to the power supply than the section you've shown. Seems like there's a main supply and isolated ones for the 2 channel and the DMM. For start I'd check the voltages for these.

author: Zucca
author_rank: Unknown
timestamp: July 12, 2018, 06:46:20 am
content: Here you can find the schematics as wellhttps://www.eevblog.com/forum/testgear/tek-ths720a-portable-scope-teardowndiscussion/

author: TekTHS720A
author_rank: Newbie
timestamp: July 21, 2018, 01:46:42 am
content: Thanks for the details. Been distracted with another problem--Will update this blog when I find problem or develop strategy.
[solved] Help identify LiIon overvoltage protection IC - Page 1
Forum section: electronics / repair

author: abyrvalg
author_rank: Frequent Contributor
timestamp: July 21, 2018, 12:41:50 am
content: Two identical ICs in a 10s Li battery controller of Xiaomi M365 electric scooter failed short on all inputs. They didn't explode thanks to 1K series resistors and drained many cells to 0V (should I really thank those 1Ks?).Drawing a partial schematic suggests a charging overvoltage protector.WSON8 package (no leads), no exposed pad, marking: L04A EV. Bottom side marking seems to be a date code (8A on one, 8N on the other). The other components are mix of brands, no favor to any (MagnaChip power FETs, TI BQ7693003 monitoring AFE, STM8L MCU). TI has some similar small ICs, but none matches the pinoutEdit: solved, it’s an R5434D by Ricoh
Rigol DP712 "Fan abnormality" message - How to clear it? - Page 1
Forum section: electronics / repair

author: AndersJ
author_rank: Frequent Contributor
timestamp: July 20, 2018, 11:30:01 am
content: The message "Fan abnormality, output disabled" is shown on the display.The message appeared when I disconnected the fan to measure the current,hoping to replace it with a lower noise fan.The message persists, and the output is disabled, with the (original) fan connected and running.How do I clear the message, and restore normal operation?/Anders J

author: _Wim_
author_rank: Super Contributor
timestamp: July 20, 2018, 02:59:36 pm
content: Is it a three wire fan with speed feedback? If yes, could it be that the fan connector was connected incorrectly (only 2 pins connected) Did you connect the connector reversed (+ and - the other way around)?Did you turn power completely off (iow removing the power cable)?

author: AndersJ
author_rank: Frequent Contributor
timestamp: July 20, 2018, 05:44:30 pm
content: Two wire cable, correctly connected.Complete turn off.Only visible anomaly is that the fan is not physically mounted on the chassis.I doubt that the controller can detect that.

author: _Wim_
author_rank: Super Contributor
timestamp: July 20, 2018, 06:22:04 pm
content: Quote from: AndersJ on July 20, 2018, 05:44:30 pmCould be the reason. The controller probably monitors the power consumption. This is the reason why sometimes an additional resistor is added to dissipate some additional power when a "silent" fan is installed..When air flow is retricted, power consumption is higher... Try to restrict air flow with your hand and check if the problem goes away or reinstall the fan in its normal position...

author: AndersJ
author_rank: Frequent Contributor
timestamp: July 20, 2018, 07:24:48 pm
content: Just to clarify, I’m still using the original fan.Haven’t found a silent 70 mm fan yet.Hand restriction did not work, or I did it incorrectly.But,when I put it back properly, the error message disappeared.The speed is high for a few seconds right after turn on.Maybe it does some form of diagnostics.I remember thinking it took longer to rev down when the fan was out of the case.Perhaps that was the timeout, when it gave upp looking for a proper fan?I didn’t realize a simple chassis fan could be so sophisticated.I need to analyze this better.Thanks for broadening my thinking.

author: jmelson
author_rank: Super Contributor
timestamp: July 20, 2018, 08:09:52 pm
content: Quote from: AndersJ on July 20, 2018, 07:24:48 pmThere may be a self-heating thermistor on the main board that senses that the fan is cooling it.Jon
Can you help me identify this transistor? - Page 1
Forum section: electronics / repair

author: joseph nicholas
author_rank: Frequent Contributor
timestamp: July 20, 2018, 12:41:45 pm
content: Hi I found this part in an old Portland tv. Can anyone tell me what it is? I tried google and only this picture showed up, no information.I would like to find a replacement but dont know were to start. The package is not important. I think it may be a voltage regulator or some kind of a diode. Just not sure.Thanks in advance

author: andrzejj
author_rank: Contributor
timestamp: July 20, 2018, 01:20:20 pm
content: This:http://elektron.uw.hu/catalog/CROSSREF1.pdfStates that it can be replaced with STR382, which is 125V, 20W voltage regulatorSome datasheet in japanesehttp://pdf.datasheetcatalog.com/datasheet_pdf/sanken/STR212_to_STR385.pdf
Where is a good place to buy IGBT Transistors  IRG4PF50W - Page 1
Forum section: electronics / repair

author: Johnny10
author_rank: Frequent Contributor
timestamp: July 30, 2018, 04:20:37 am
content: Wondering where you shop for good quality transistors? And other discrete parts.Still repairing the Phase Three Battery Charger and I found this is an extremely good quality PCB and components.Want the repair to use good quality parts as well.My local surplus electronics store closed where I could always find quality components for low dollars.Bought a lot of marginal short lived parts from China through eBay and Amazon but I have decided to give up those suppliers.

author: Circlotron
author_rank: Super Contributor
timestamp: July 30, 2018, 04:24:33 am
content: MouserDigikeyElement14RS components

author: coromonadalix
author_rank: Super Contributor
timestamp: July 30, 2018, 10:21:58 am
content: ElectosonicAvnet

author: keymaster
author_rank: Regular Contributor
timestamp: July 30, 2018, 07:30:47 pm
content: https://www.arrow.comhttps://www.distrelec.biz
Tektronix 2430A Troubleshooting Help - Page 1
Forum section: electronics / repair

author: Vairemont117
author_rank: Newbie
timestamp: July 11, 2018, 05:54:22 pm
content: I have a Tek 2430A scope, and upon power up it beeps, lights up the GPIB lights, displays a few vertical lines of dots and several random curved lines, then the screen goes blank and the GPIB lights go off. I am currently following the Dead start Troubleshooting section of the service manual, but I cant seem to find anything that pertains to the random dots and lines. Anyone have any clues as to what might be going on?

author: siggi
author_rank: Regular Contributor
timestamp: July 11, 2018, 07:32:15 pm
content: My 2430 behaved similarly due to dead RAM. Did you try the kernel test.Sent from my iPad using Tapatalk

author: Vairemont117
author_rank: Newbie
timestamp: July 12, 2018, 02:17:43 pm
content: I ended up swapping it with a spare processor board that I had from a previous scope and it works now. Well I say works, it loads up and runs the self tests now, fails several 7000, 8000, and 9000 tests.

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 19, 2018, 04:46:02 pm
content: I have 1 of these, how long on till they become a collector's item when hardly any rare original parts are still working ?
VTech phone repair - Page 1
Forum section: electronics / repair

author: philm
author_rank: Newbie
timestamp: July 16, 2018, 01:31:42 pm
content: Hello,I am having an issue with a VTECH CS6238-4 cordless phone. The "In Use" LED is constantly blinking.I received this through a garage sale. The wireless phones are all dead and need charged. But, I am unable to do anything since the In Use led is blinking. The phones "charge" then turn on and says that the phone is unable to detect the base station because it has no power or is in use. The phones then turn off. This cycle repeats.I was wondering if anyone has had an issue like this before and if anyone knows of a solution? Thank you.

author: philm
author_rank: Newbie
timestamp: July 19, 2018, 12:23:04 pm
content: Anyone?
strange ripple on 3€ 12V 1A power supply - Page 1
Forum section: electronics / repair

author: webgiorgio
author_rank: Regular Contributor
timestamp: July 17, 2018, 12:02:48 pm
content: This switching power supply from ebay (CD-01218) has a severe noise on the output voltage.The input is at 50 Hz, and the noise "blocks" are in phase with the supply voltage.The scope has 10 ms/division, and 1V/division.What could be the reason for this bad voltage output? attached photo of the oscilloscope

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 17, 2018, 02:01:40 pm
content: I would say: typical CE (=china export) phenomenon. Lousy design. I had once one where the big cap on the DC side blew up when nominal current was reached, likely because of a combination of poor quality cap and too high ripple/noise on the DC.I don't know if it really worth it, but you can try blocking some more noise with chokes and further caps, but you'll likely fast exceed the 3€ with that material

author: Zucca
author_rank: Unknown
timestamp: July 17, 2018, 02:13:25 pm
content: Test it again under load... and see what happens

author: webgiorgio
author_rank: Regular Contributor
timestamp: July 17, 2018, 03:17:25 pm
content: With a 3W load it goes worst, with peaks at 17 V.With 10uF in parallel on the load it improves, but still a lot of spikes (+-1V).Sure it is a low quality Power supply. It was working fine earlier, powering an arduino. The the Arduino got mad, I checked the PSU and found it guilty.Seems like a fault.Several years ago I purchased 10 pcs of this power supplies from ebay, and they all fail after 1-2 years of operation.The curious thing is that those "blocks" of spikes are aligned with the peaks of the 230V supply voltage.Maybe someone recognise that "shape" of the signal as a "typical" fault?

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 17, 2018, 03:30:40 pm
content: could be an underdimensioned cap after the rectifier, not only it is lousy designed for its proper purpose, it obviously misses all measures against EMI as far as I see; I wouldn't like on mains running in my shack.you go the old way: if you buy cheap, you buy double in the end. it's not worth troubleshooting; in the bin with it and get something decent

author: Cyberdragon
author_rank: Super Contributor
timestamp: July 19, 2018, 02:29:04 am
content: Show us the underside and close ups. I bet there's a lot more wrong with it (safety wise) than just ripple.
[NEVER MIND] "Laptop style" SMPS: MOV marking seems wrong, how should I replace? - Page 1
Forum section: electronics / repair

author: mad_mav
author_rank: Newbie
timestamp: July 17, 2018, 10:42:08 am
content: Hello world =)The SMPS of my speakers went bust and as it is hard to find a replacement (27V 1.2A !)....Inspection shows a Rapid Unplanned Disassembly of the fuse (totally exploded into pieces...) as well as of a MOV parallel to the primary side electrolytic capacitor. The capacitor seems dodgy: sometimes it would measure healthy on the LCR, sometimes non-existing.. So I'd suspect the failed capacitor might have allowed for a surge during switching which busted the MOV which created short circuit for primary... Replace them all.. But wait..The capacitor is 400V, so according to a 10% transient overload 440V should be the absolute maximum for a MOV parallel to it. The MOV however is only marked with "1kV" (no model number)! I'm tempted to replace it with something like a MOV for 350V operation/430V clamping, as it seems like the right protection for the capacitor. Yet I'm more of a 5V monkey and do not know much about power supplys - what would you suggest?On a side note: I had to dig myself through the silicon stuff they almost potted the thing with - is it OK to use hot glue during assembly instead, or is it a no-no at high voltage?

author: drussell
author_rank: Super Contributor
timestamp: July 17, 2018, 12:17:07 pm
content: Are you sure it is a MOV and not just an across-the-line capacitor for EMI reduction?Perhaps you could post some photos?

author: mad_mav
author_rank: Newbie
timestamp: July 17, 2018, 02:14:45 pm
content: OK, now I feel silly... This blue disc thingy collected from pieces was probably just a ceramic capacitor that failed short in parallel to the electrolytic and not a mov..No usual RU etc markings here though... There is a separate capacitor on the AC side too...
ps23023 - Page 1
Forum section: electronics / repair

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 12, 2018, 06:18:34 am
content: Hello everyone! I am in the process of rehabilitating a laboratory supply that is now functional. By surrounding it; I realized the presence of a potentiometer found RP9 next to the integrated circuit LM741 (position: N2). The other potentiometers adjust the current and the maximum output voltage, and for this potentiometer I think of an offset setting. How should you go about fixing it? Thanks for your help

author: Relayer
author_rank: Contributor
timestamp: July 12, 2018, 10:39:49 pm
content: Hello lionelkjh,QuoteI'm fairly certain that RP9 is to adjust the offset null. Therefore itshould zero out your voltmeter when you have the voltage control set to zero.I hope it helps.Regards,Relayer

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 16, 2018, 02:16:40 pm
content: Hello; I tried: but it does not change anything in output; yet voltage potentiometer set at least in continuous mv position. An idea??

author: AlcidePiR2
author_rank: Regular Contributor
timestamp: July 16, 2018, 03:49:37 pm
content: Hi,MaybeYou can read this threadhttps://www.eevblog.com/forum/repair/tuning-a-ps23023-power-supply/

author: lionelkjh
author_rank: Frequent Contributor
timestamp: July 17, 2018, 01:18:43 pm
content: 163/5000I try by all means, and the multimeter always gives me a tension, and the setting does not change anything ..... Can someone help me with a scheme??

author: HB9EVI
author_rank: Frequent Contributor
timestamp: July 17, 2018, 02:13:57 pm
content: As far as I see this opa is part of the current regulator, not of the voltage regulator; so you're adjusting the current offset, not the voltage offset of the PSU
Eaton (MGE) Evolution UPS repair (help) - Page 1
Forum section: electronics / repair

author: +Mikie
author_rank: Contributor
timestamp: July 17, 2018, 01:41:12 pm
content: My first post here and it's asking for help... Doesn't look good, does it?In any case - I need a bit of assistance fixing this UPS. It does not charge batteries (I've checked). It will run correctly on a charged set until they are drained, at which point starts complaining.I actually have another working one, and my first suspect was a H-bridge nearest to the batteries with MOSFETS specced for under the mains voltage. They measured differently to the working set, so I changed them, but no joy. I've tried running the supply while opened to measure few things, and I noticed that another single MOSFET is getting fairly hottish and is also not measuring the same as the working one, so I'm waiting for a replacement. We'll see how it goes. Other H-bridge MOSFETs are specced above mains voltage, so I don't think I should be looking there because it outputs the correct voltage. It's just this stupid charging problem.What is unclear to me is the fairly small transformer that doesn't look like a 600W capable. Upon some searching and reading, I figure that its' the patented MGE high-frequency square wave "modulated" mains, so that would explain smaller size. Higher frequency = higher transformer efficiency.Anyway - if anyone is willing to have a go at this with me, it would be appreciated. I can provide any number of photos, but unfortunately no schematic. One Perth repair company answered my email with a standard confidentiality drivel, so I didn't bother asking elsewhere. I admire their loyalty to a company that no longer exists, but it is a bit stoopeed.
Samsung s27b970d keeps flashing color test patterns - Page 1
Forum section: electronics / repair

author: heatbreak
author_rank: Contributor
timestamp: July 28, 2018, 11:13:12 pm
content: Hey there,It was flashing color test patterns RED, GREEN, BLUE, WHITE, GREY, Color Bars intermittently. Sometimes it starts flashing on power up and sometimes after working normally for a few minutes then reverts back to working normally. Now, it mostly stuck at flashing test patterns continually (even if all video input (dvi, dp, hdmi) are left disconnected). It has a Samsung LTM270DL02 panel. I've attached a few pics showing the main logic board and what the test patterns look like. The main board has three connectors going into the neck: one to power/control the touch control controlling the on screen menus. one for powering the panel and backlights. and one for the lvds signals. If I unplug the lvds cable (at the connector marked as WHITE) when the monitor is working normally, then the panel would automatically cycles thru the various colr test patterns by itself. So that makes me think that's the default action for the panel's T-Con board when LVDS signals are missing? I've probed the LVDS traces (the WHITE connector) and it seems like all of the clock signals are missing. So either the FPGA is dead (cold solder maybe???) or somehow the mainboard is stuck in self diagnostic mode for some reason? I read thru the user manual and there's no mention of such self diagnostic mode. btw, the on-screen menus do not appear at all when it's flashing those test patterns.Any ideas on how to proceed further?https://imgur.com/a/kLzhpxTTIA
Benq BL2710PT, need some help with identification of IC - Page 1
Forum section: electronics / repair

author: bugmenot
author_rank: Newbie
timestamp: July 15, 2018, 07:33:45 am
content: Yesterday thunderbolt blew up PSU in my BL2710PT monitor. I'm going to have it fixed in some service, because my knowledge is limited by replacing broken capacitors/fuses/transistors. But I just want to make it easier for serviceman to identify that IC, if it's hard task. I don't think that they have expirience in fixing such monitor. Maybe some of you could help me with identifying that IC. I'm attaching photos of internal power supply PCB, and blown up IC. I found one small piece of it, but still it's not enough to see full name and google it.The rest of components don't look special, so probably it won't be hard to change them. Feel free to ask for any additional info/photos.

author: bugmenot
author_rank: Newbie
timestamp: July 15, 2018, 09:08:23 am
content: TEA1751T ?

author: bugmenot
author_rank: Newbie
timestamp: July 16, 2018, 07:18:02 pm
content: Yep, it's TEA1751T, Yesterday I wrote letter to official techsupport of Benq in russia, and they answered to me with very informative answer and said that it's TEA1751T, and additionally gave couple of PDF files with scheme of monitor PCB's.Did not think they can answer like this. Theme can be closed now, I suppose.

author: amyk
author_rank: Super Contributor
timestamp: July 17, 2018, 01:42:38 am
content: Benq's reputation just increased a few points for me... usually only something companies like "old" HP would do
Hartmann & Braun, Pontavi WH2, repair schematic - Page 1
Forum section: electronics / repair

author: carbono.silicio
author_rank: Contributor
timestamp: July 16, 2018, 08:09:09 pm
content: Hello all,I've bought this used Volt/Ohmmeter and would like to restore and repair it.Hartmann & Braun, Pontavi WH2From a quick look inside everything looks ok and the needle is also ok but i can't get Resistance reading.Does any one have a full schematic of the circuit? The online manual only shows part of it.Thank you very much,Nelson
Heil HM-10 Dual repair - Page 1
Forum section: electronics / repair

author: innkeeper
author_rank: Unknown
timestamp: July 16, 2018, 04:11:28 pm
content: I got my hands on a Heil HM-10 Dual element microphone at a hamfest that in pretty sad shape but salvageable.If anyone can take a picture of a Heil HM-10 Dual microphone elements and how they are mounted, that be great!The microphone elements broke loose from the mount at some point and it seems someone thought the solution for that was duct tape... which has now become all gooey. What a mess. it is otherwise coated with a thick layer of nicotine stains, in the pic below, the ring on the top of the mic is supposed to be silver and not gold looking and the lettering should be white. Though I think this can all be cleaned up.its also missing the screw that held the mic into the body. you can see where someone had put tape along the base of the mic, where they held a wrong sized screw in place to keep the mic jack in the mic body. the previous owner loved tape I guesswiring all seems ok. it doesn't look like anyone has messed with the insides.the elements look like they might have been epoxied to the top of the plastic mount but, I've seen pictures of the inside of an HM-5 where the elements had a holder and were mounted vertically. I don't think this is the case for this one as there simply isn't enough room for that.
Identification of a voltage regulator IC - Page 1
Forum section: electronics / repair

author: warnings
author_rank: Newbie
timestamp: July 17, 2018, 06:07:15 am
content: Someone put a wrong power supply in a box seem like new because all packed well.I plug the 12v power and nothing but when I look a little more, someone put a 12v power supply instead of 5V in the box !Now a component has melted and I can ask to the manufacturer for retrieve the component name but not help me a lot.Main power : 5VReference : LD5PA (LD = LDO voltage regulator; 5 = 5V and PA ?)Package : SOT23 - 5 PinsIt's a step down 5v to 3.3v or only a 5v voltage regulator ?Thank you for your help

author: borghese
author_rank: Regular Contributor
timestamp: July 17, 2018, 06:32:54 am
content: Some photos would help

author: amyk
author_rank: Super Contributor
timestamp: July 17, 2018, 11:44:11 am
content: Probably SY8088 --- input voltage 2.5 to 5.5V, smoking at 12V would seem to fit.
Replacing old LCD or VFD displays using an emulator/microcontroller? - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 15, 2018, 11:45:23 pm
content: I'm thinking of mainly of 7-segment displays but that other kind too (Vacuum florescence display) ?If you have some old equipment with a broken display, but the chip still works, how hard is it for someone with programing skills, have a micro-controller like Ardino basically translate the signals and run a nice big modern LCD ?Or if the display chip is broken, how hard is it to take it's input with a MC (or some FPGA magic I don't know about) and basically emulate what some 1970s 1980s display chip should be doing, then feed it to any old display ?Or if u just want to add a nice big modern LCD, even if it only shows the main numbers, and not all the side info on screen. And so hacking that onto an old bench DMM for example ?And what about just feeding right off the original 7-seg display inputs, and just adding a big $2 one off ebay (or whatever they cost ). Is that an easy mod ? I don't mean the original chip would have to drive the new LCD, just reading whats going to it and driving the new 7-seg display.

author: sokoloff
author_rank: Super Contributor
timestamp: July 15, 2018, 11:50:50 pm
content: Some good discussion here where someone made an LED replacement for an LCD on a 3457a.https://www.eevblog.com/forum/projects/led-display-for-hp-3457a-multimeter-i-did-it-)/msg1345741/#msg1345741

author: james_s
author_rank: Super Contributor
timestamp: July 16, 2018, 01:38:18 am
content: It can range from trivial to quite involved depending on the details. The first thing I'd suggest doing is take a look at what's driving the display, then you can decide whether it's easier to try to repurpose the existing driver or build something new that picks up the data being sent to the original driver. Quite a few displays will have a driver that uses SPI or something similar although in lower cost equipment the display may be driven directly from a custom microcontroller.
Computer PSU low 3.3Vrail, why does this cap charge different - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 14, 2018, 08:09:51 am
content: I have broken PSU I've worked on before, and had most of it apart. Today I finally measured the 3.3Vrail while it tries to start (w&w/o PC).So with a Tek2430 scope, and found it only gets to about 1.5V hooked to the PC, 1.7V w/o PC, and just sits there. The supervisor chip waits 75ms before shutting it down.The trace of this tho does not look like a normal cap charging, it looks more like a parabola. It only takes 1ms to get to about 1.3V, and then it takes even dips a bit for 10ms, then by 30-40ms it at 1.5V (or 1.7Vw/o load)The 5 and 12V rail look like normal exponential charging curves. The 3.3V trace starts slow, like a parabola, with a normal vector pointing to the upper-left. Sounds strange to me but I'm pretty green.I actually I had most the cap's out and did ESR tests, so IDK. I'm about to map the 3.3V section.

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 15, 2018, 10:29:53 pm
content: I mapped it out and it uses a tl431 to control a shunt transistor, so I recorded all the voltages last night. And it wasn't working for sure. And it hasn't the many many times I've turned it on over the last few months.Then today it's MAGICALLY working, so I tried it on the PC and indeed it is working fine.Since last night I might have moved the shunt transistor to read it better. And a 15Ohm resistor between V33 and V5 . So maybe it was loose? That doesn't account for the voltages tho.Before when I injected 3.3V after the V33rectifier diode it would use 340mA, which was crazy. Now it's at about 40mA which is about right.I've cleaned this thing multiple times because I de-soldered a lot of stuff as a learning project, testing it all.Worst thing is I really can't say why it didn't work when I bought it. Since then I fried 1 MOSFET by accident, replaced it.Then I replaced a CM6800, but I didn't understand it was being latched off. I have to find the original and test it again out of circuit again...it didn't seem to work out of circuit so IDK.I did replace a broken PFC gate SMD transistor, but I might have fried that with my iron.And now today it magically works? Did some solder ball fall off since last night?
Cisco Catalyst 3560 POE - pregnant capacitors - Page 1
Forum section: electronics / repair

author: amstel
author_rank: Newbie
timestamp: July 15, 2018, 05:11:34 pm
content: Hi guys,I have a Cisco Catalyst 3560 POE-48, which have been used in the production.Since yesterday it has started to reboot every 5 minutes.I opened the case and noticed that the power supply capacitors looks fine fine but the capacitors on the board looks bad.Please could you advice which series of Panasonic's capacitors shall I use to recap?EB has got Lifetime @ Temperature: 10000 hours @ 105°COverkill?1800u 6.3V1000u 16V
Tektronix 2430A switching from 50-100us moves CH1/2 down - Page 1
Forum section: electronics / repair

author: lordvader88
author_rank: Frequent Contributor
timestamp: July 14, 2018, 06:30:48 am
content: I have 2 working CCD chips finally, and all tests pass. Today I notice that when changing from 50us to 100us, CH2 trace moves down about 1-2mm, and ch1 about 1/2mm, thats on all V/div and when GND coupled also.What might do that ?

author: Testtech
author_rank: Regular Contributor
timestamp: July 14, 2018, 10:45:45 pm
content: Did you do a COLD START, followed by SELF CAL and EXT CAL? If not, you need to.
[SOLVED] Part number for the power switch from an HP/Agilent E3610A power supply - Page 1
Forum section: electronics / repair

author: bluebird
author_rank: Contributor
timestamp: July 14, 2018, 08:04:59 pm
content: Update: From trial and (thank God no error) I've confirmed that the 3101-3230 power switch in the E3610A service manual is the same as NE182AEE6AMP from thelatest part numbers. FYI the current C&K catalogdoes not reflect the part number changes.Using the same logic I believe the part number for 3101-3231 current range switch is NE182UEE6AMP.Hi friends,I recently picked up an Agilent E3610A power supply that seems to be missing only a power switch.The part number (according to the E3610A service manual) of the switch is 3101-3230. It can be ordered (according to the Keysight website) but I imagine they'd probably charge an arm and a legI've identified the switch to be a C&K NE18 series switch. This is what it looks like:Does anyone know what the exact part number is from the switch manufacturer? It seems that only Mouser has them in stock (https://www.mouser.com/CK-Switches/Electromechanical/Switches/Pushbutton-Switches/NE18-Series/_/N-5g30?P=1yzsaciZ1z0zl2x) but I'm not sure which exact one I should buy.Any help would be highly appreciatedMany thanks!
Korad KD3005D Power Supply - Fan Problem - Page 1
Forum section: electronics / repair

author: CarsonReidDavis
author_rank: Regular Contributor
timestamp: May 16, 2018, 05:44:06 pm
content: I had been using my Korad for a few weeks when I realized that the fan never seemed to run. I listened in the back and it was making a odd humming sound.So I took the unit apart and fed the fan voltage directly from a power supply and it worked fine. Then I metered the board output to the fan and it gave a reasonable voltage that should run the fan.Confused, I hooked the fan back up to the board and measured the voltage the board produced under load. This time the board failed to produce nearly enough voltage to power the fan and the fan made that same sad humming sound.Here is an album with various pictures of the PCB and descriptions from my testinghttps://imgur.com/a/xNmjzks.Any ideas what I should be looking for to fix?

author: Mosaic
author_rank: Regular Contributor
timestamp: July 14, 2018, 06:00:57 pm
content: The fan is run by a temperature triggered circuit. Probably from a thermistor feeding the wiring harness running to the front panel from where the fan gets its power.Simplest solution is to tie the fan directly to a 12V power rail and let it run when the unit is on.My Korad died after 15 minutes of first use while figuring out how the CC mode worked.Blew the main fuse.So I put in a larger fuse and heard the Transformer doing a loud buzz. Yet the front display came up.Something was loading it severely, when I removed the heavy 4 pin high current connector to the rectifier board from the xformer the buzz went away.So I let the buzz continue for about 30 sec and out popped the magic smoke near the bridge rectifier.Tested the rectifier and the two NPN power bipolars and the rectifier had 2 shorted diodes. NPNs were fine.Popped in a 35A aluminum block type bridge I had and wired it into place screwing it into the bottom of the Alum heatsink. Overkill , but I had that for years from a electronic goldmine promo sale waiting for a purpose.Unit is fixed and fine now.
Rigol DSA1030 - Page 1
Forum section: electronics / repair

author: pa3hfu
author_rank: Contributor
timestamp: July 14, 2018, 11:58:48 am
content: Occasionally my DSA1030 'hangs' on the very last end of the startup. I made a picture of it. Mostly it boots without any problems.I think one of the twenty startups it hangs. Any idea what this can be? For sure I uploaded the latest firmware again.Anyone suggestions?Thanks a lot!!Mathew

author: pa3hfu
author_rank: Contributor
timestamp: July 16, 2018, 06:16:41 pm
content: Nobody..??

author: coromonadalix
author_rank: Super Contributor
timestamp: July 16, 2018, 09:02:20 pm
content: have you asked Rigol ? maybe a file or the operating system hang on something, a bad contact or solder
A few general questions about thermal pads and copper tarnish - Page 1
Forum section: electronics / repair

author: skyhawk
author_rank: Contributor
timestamp: July 13, 2018, 03:40:56 am
content: Thisis the controller board for a 2 year old hard disk drive.The drive started displaying odd behavior and failing self-tests, so I was about to throw it in the garbage when I figured "let's take a look at the controller board for shits and giggles"2 "repairs" later using a boxcutter and a white eraser, and the drive is now back in service, and appears to be operating fineI've got four other drives of the same make and model, and I have now performed the same "maintenance" on them as a preventative measure. Am I being paranoid or are thermal pads supposed to have the plastic cover removed before they're pressed onto something?

author: helius
author_rank: Super Contributor
timestamp: July 13, 2018, 05:22:46 am
content: It's a little hard to tell, but that might be a Sil-Pad: a heat conductive silicone spacer.

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 13, 2018, 01:45:39 pm
content: Yes, the plastic cover is supposed to be removed.Tim

author: skyhawk
author_rank: Contributor
timestamp: July 13, 2018, 10:09:57 pm
content: Quote from: T3sl4co1l on July 13, 2018, 01:45:39 pmShould I be concerned about the fact a shiny new drive (made probably about 2 years later) has the exact same plastic on the thermal pad?

author: T3sl4co1l
author_rank: Super Contributor
timestamp: July 14, 2018, 08:30:26 am
content: Probably not. It's been working for them so far...Tim
Tascam US-4x4 - worth trying to fix? - Page 1
Forum section: electronics / repair

author: CRTBeam
author_rank: Newbie
timestamp: July 13, 2018, 04:51:35 pm
content: So, my trusty audio interface has released the magic smoke. I don't fully know the cause, but i suspect transient on the usb side of things. It blew a hole in the main CPU wich is LPC1820FBD144. So the question is, will replacing the CPU will make it work again? There is a little 8-pin flash(MXL25L4006E, to be precise) and there is a usb software tool for updating firmware. The only programming header on the PCB is connected to this little flash. The chip has a hardware USB support so it should be recognised by the PC(I think). Getting the chip in single quantity, proved to be difficult, also prices aren't the lowest. So should I pay $40 for a chip and try, or should i save up for a new interface?

author: helius
author_rank: Super Contributor
timestamp: July 13, 2018, 05:46:11 pm
content: LPC1820FBD144 has no on-chip Flash or EEPROM, but you should verify it has no configuration fuses that need to be programmed.Transient on the USB side shouldn't fry the chip. There are TVS diodes to protect it. I would check the power supply isolation.

author: CRTBeam
author_rank: Newbie
timestamp: July 13, 2018, 06:38:19 pm
content: It has OTP memory. I found a pdf describing it. Sadly I don't really know what should be written to it. I'm a noob when it comes to the microcontrollers. Should BOOT_SRC be changed to SPI (little flash chip)?
Components identification - Page 1
Forum section: electronics / repair

author: dovydas1928
author_rank: Newbie
timestamp: July 13, 2018, 01:03:57 pm
content: Hello,Could someone tell me part numbers of these two chips?1.:NXP16048504L0A3A040UnG10143 <- this should be the marking2.:014JM02AD89551 <- this should be the markingRegards,Dovydas
Acer PC monitor repair - Page 1
Forum section: electronics / repair

author: Valentin Part
author_rank: Newbie
timestamp: July 13, 2018, 12:25:49 pm
content: Hello everybodyI'm trying to repair my Acer PC monitor. I found that the power supply has some issues. A transistor (SSS6N60A, N-Channel Mosfet) is obviously broken. The drain source path stays conductive all the time!My question is, if I can replace the SSS6N60A with a newer 2SK2645.Attached you can find the required datasheets.Thank you in advance!
Gate motor repair, ATA ELITE SGO-1 - Page 1
Forum section: electronics / repair

author: wilfred
author_rank: Super Contributor
timestamp: July 13, 2018, 05:53:20 am
content: /.

author: CJay
author_rank: Super Contributor
timestamp: July 13, 2018, 07:49:25 am
content: Could be the grease on the motor bearings, could be the bearings themselves, maybe swap the motors side to side and see if the fault follows the motor?An ammeter to measur ethe current drawn by the 'slow' motor might reveal something.
Netgear GSM7224v1 Switch Not Booting, Electronic Fault  - Page 1
Forum section: electronics / repair

author: Pesle
author_rank: Newbie
timestamp: November 16, 2017, 01:59:03 am
content: Hi all,So it all started when I rebooted my switch, and it would not come back on and had all lights on and no serial messages. I fixed this as there was a capacitor blown which was apart of the regulator circuit (RAIL 1 In Photo) for the ASIC. Once that was fixed, i started getting serial messages, but they would do exactly what these threads were doing:https://community.netgear.com/t5/Wired-Network-Adapters/GSM7224v1-Does-Not-Boot/m-p/423784#M932https://community.netgear.com/t5/Managed-Switches/GSM7224v1-Boot-problem/m-p/406295#M238One solution was to cover it under warranty would not apply to me as I have replaced the fans with larger ones on the top, and I bought it off Ebay for $20...Another solution was to try reseting then reflash the Operating Code, which I did using the serial connection, and it did nothing.Looking further into the issue, the regulator circuit (RAIL 2 In Photo) for the SerDes is returning 0V and a really low resistance compared to RAIL 1.I have a schematic for the regulator circuit:https://www.intersil.com/content/dam/Intersil/documents/isl6/isl6444.pdfSo I MIGHT be able to trace it back to a fault.Just wondering if anyone else has even gone this deep into repairing one of these switches as there's basically nothing online about repairing them or anything similar.I'll update on what I find.

author: Riotpack
author_rank: Regular Contributor
timestamp: November 16, 2017, 06:02:08 am
content: Did you test the other caps? Sometimes they go bad without looking it.

author: Zucca
author_rank: Unknown
timestamp: November 16, 2017, 09:28:57 am
content: Thermal camera to see if something is burnig on RAIL 2, but of course you don't have a TIC.desolder regulator on RAIL 2 and check if it works off board.connect a Lab PSU in place at VR RAIL 2, slowly ramp up the voltage, check ampere flowing, and with your fingers if something is getting hot.I would replace all the caps, with good new ones.

author: Pesle
author_rank: Newbie
timestamp: November 22, 2017, 03:34:32 am
content: Sorry for taking so long to reply, I got busy with work and what not. I replaced the other capacitor and I now have voltage. For anyone attempting repair, RAIL1 is 2.5V and RAIL2 is 1.1V (at least for me).Thank you all very much

author: Werecow
author_rank: Newbie
timestamp: July 12, 2018, 07:56:48 pm
content: Not quite a necro thread, so...I use three of these switches; two at work, and one at home. All three had capacitor failures, intermittently causing the same almost-but-not-quite-booting condition you described. In one, the six 1,000uF 16V failed, and in another, both 1,000uF 6.3V caps failed. The third switch had only 2 caps fail, both 1,000uF 16V.I'd strongly recommend that you schedule time to replace at least every 1,000uF in that switch, because they all have the same run time, all had the same amount of heat and stress applied, and they're all the same Teapo brand. The fact that 'Teapo' rhymes with 'cheapo' isnota coincidence.
Agilent  E4402B Spectrum Analyzer repair  Align Now All Required - Page 1
Forum section: electronics / repair

author: startronic
author_rank: Contributor
timestamp: July 09, 2018, 08:33:43 pm
content: Hello Guys,...I have an Agilent E4402b, with the display message Align now All required, even after doing the procedure Align Now, after restarting the E4402 back with the same problem, in the system menu in Shows errors appears the error code - 222,I reshoot Aling Now again, and now you get the message DATA OUT OF RANGE on the display.Here in Brazil Agilent (Keysight), not of due support, say that it is already obsolete.So I'll have to fix it myself,I would like to request judo from the forum forum, if any have the service manual for this model I am very grateful.Thank you

author: Samogon
author_rank: Frequent Contributor
timestamp: July 09, 2018, 09:15:53 pm
content: Cmos battery is dead.

author: chrisl
author_rank: Regular Contributor
timestamp: July 09, 2018, 09:16:52 pm
content: Most likely the internal backup battery needs to be replaced.You should be able to find one off Amazon.https://www.amazon.com/gp/product/B005B0HV2O/ref=oh_aui_detailpage_o00_s00?ie=UTF8&psc=1

author: startronic
author_rank: Contributor
timestamp: July 12, 2018, 12:29:14 pm
content: Thanks, my friends, Chrisl e Samagonworked perfectly
Help me identify this component "A91Cd" - Page 1
Forum section: electronics / repair

author: Armadillo
author_rank: Super Contributor
timestamp: July 11, 2018, 03:08:33 pm
content: Was repairing Antec 750W and came across this component marking "A91Cd" that I have never seen before.Wonder what device is that.Thanks;

author: 4thDoctorWhoFan
author_rank: Regular Contributor
timestamp: July 11, 2018, 03:21:27 pm
content: I believe that a A91 translates to a BAS17.If you google BAS17, you should easily find a datasheet. It's basically a diode between two of the pins.

author: cvanc
author_rank: Frequent Contributor
timestamp: July 11, 2018, 04:18:54 pm
content: One of the solder joints on that thing looks highly suspicious, FYI...

author: Armadillo
author_rank: Super Contributor
timestamp: July 11, 2018, 06:29:02 pm
content: Thank you both for reply;@4thDoctorWhoFan - Thanks, but I really don't think is a low voltage stabistor. I don't think this device would be used in PC power supply, would it? I don't know really. It near the LED side of the opto-isolator EL816, all 3 legs are used, hence I am inclined to think is the TL431 variants, not sure,. guessing.@cvanc - Thanks for reply. Just checked and confirmed, its the lighting & shadow effect. Visually checked and continuity checked [pin and solder/track]

author: amyk
author_rank: Super Contributor
timestamp: July 12, 2018, 01:26:15 am
content: That would be anAP431AR.
Tektronix 2215 scope - Page 1
Forum section: electronics / repair

author: rharrison486
author_rank: Newbie
timestamp: July 11, 2018, 12:37:03 pm
content: Hello I've been given an oscilloscope to play around with it's a Tektronix 2215 but it has a fault. I'm tryingTo get a trace but all I can seem to get is a vertical line on the screen when beam find is pushed. If anyone knows what would be causing this that would be great.

author: Specmaster
author_rank: Super Contributor
timestamp: July 11, 2018, 01:00:51 pm
content: That would be indicating that you have no sweep function on the timebase which controls the horizontal trace. You have a vertical line which would be giving a basic indication that the vertical amplifier section does seem to be working.

author: GoodCrossing
author_rank: Contributor
timestamp: July 11, 2018, 07:41:16 pm
content: Tektronix still has the service manual on their website - it will help you narrow down the problem. Take a look at the back to see if it has an OPT 48 sticker. If so, remember that the component list will be different for some boards, at the back of the manual it tells you the changes.