hybridfree/eevblog-posts huggingface dataset:
DC Ohms not working on LCR meter ? - Page 1
Forum section: electronics / repair

author: MathWizard
author_rank: Super Contributor
timestamp: July 11, 2020, 07:23:58 am
content: I have a MS5308 LCR meter, and today I noticed the DCR is not working, shorting the probes gives 34R., and it thought a 1pF cap was 100RI've never had this near live voltage, and it been ages since I tried looking at caps that would have ever had more than 10-15V on them, and they should have had no charge on them, since everything I worked for ages, all drains themselves in circuit.I had this apart before, and seem to remember there's only 1 IC, and barely any other parts. So if that fails, I hope they are a retail part.Any thoughts ?Just now it does go OL with a cap on DCR, but the cap it an expensive 1kV 1.0pF cap, yet it reads as 1152pF at 100Hz w/ D=0.088, and at 100kHz its 808.9pF and 0.067, ESR 132.4R, the capatitance being of that much sounds wrong. My DMM says 20pF at DC, 50pS=20Gohm DCR
Voltcraft DPS4005 DC Power supply constant current mode - high output ripple - Page 1
Forum section: electronics / repair

author: Momchilo
author_rank: Regular Contributor
timestamp: June 17, 2020, 05:21:02 pm
content: Hi,I have an old cheap Voltcraft DPS4005 lab power supply for DC output. It's split into four boards.1. power output (AC power in - main DC out)2. aux power (AC power in - +/-15V etc. out )3. linear control board4. digital boardIf it's in constant current mode the output ripple reaches up to 1.3Vpp @0.4VDC with a 6.75Resistor as load (ripple1.png).With exact the same settings, the ripple almost disappears whenever the power board is lifted few centimetres above the bottom of the case (ripple2.png).If the power board is insulated with a sheet of cardboard from the case the output ripple is ~300mVpp.The voltage across the isolated negative DC output and earth is 10Vpp @50Hz. The case is connected to earth.In constant voltage mode the ripple is below 3mVrms.So I guess the ripple comes from a capacitive coupling between the power output board and the case. But even when I connect the isolated DC output to Earth, the ripple stays the same. And why it's only in CC mode? I don't know if it's by design or a fault. I found the schematics, maybe someone else has an idea what's wrong.Thanks for your help.Best regardsMomchilo

author: TheMG
author_rank: Frequent Contributor
timestamp: June 17, 2020, 06:18:40 pm
content: Check caps in the circuit around U3 (current sense amplifier) and U4 (current limit comparator). Also carefully inspect for any broken solder joints or connections. Bad capacitors or poor connections could allow noise to be introduced into the current amplifier and comparator circuit, which would cause the kind of thing you're seeing.You could also use your scope to probe the input pins of the two opamps and trace back where the ripple is being introduced into the current feedback loop.As for the 10Vpp from earth to the isolated DC output (as measured with a high impedance DMM), that's pretty much par for the course, it's capacitive coupling resulting from interference suppression capacitors CY4 and the capacitance between windings in the transformers.
DC power supply QW-MS3010D not working properly - Page 1
Forum section: electronics / repair

author: Dvsr
author_rank: Newbie
timestamp: November 06, 2020, 06:40:09 pm
content: Hi. I am electronics hobbyist with low budget so as my bench power supply I have this chinese junk. It is supplying voltage and current but it is unstable and current limiting has never worked. When I set some current limit and start to increase the load the CC light starts to flicker and power supply starts to make hissing/crackling noise and it allows the current to rise above set limit. Now the power supply is making constant noise and the current it supplies keeps jumping.I am noob in diagnosing and fixing electronic devices so I have no idea where should I start looking. I can't see any physical signs of faults. Some solder joints seemed suspicious and I soldered them better but that didn't make any difference.I took a video of this power supply under load and I uploaded it on Streamable:https://streamable.com/yb7ygsThank you in advance for help and tips! I greatly appreciate it
Dc to Dc power supply shutting down  - Page 1
Forum section: electronics / repair

author: rantwhy
author_rank: Contributor
timestamp: August 08, 2020, 08:40:08 am
content: I have a Panasonic PTZ controller that stooped working last week.I have taken it apart and found that the fuse has blown and 2 transistors and 2 diodes have failed.There are 4 voltage rails 8,7,5 and 3.3The 3.3 is fineThe 8 is going through a linear regulator and looks fine.The 7 is the one with the failed transistor and diodes.The 5 is at 4.5 volts.I have connected the 12 volt input of the controller to a bench-top power supply current limited at around half a amp and have bypassed the fuse for now.The problem is if you give the circuit in the picture below more then half a amp the circuit will shut down.If I force 5 volts on the 5 volt test point of the circuit to test if the PTZ controller works it will take about 1 amp on start up and settle down to half a amp. But for some reason the DC to DC circuit will not support more then half a amp.Im assuming there is a over current shutdown built in somewhere that is doing this. There is no dead short and nothing is getting hot. Im stumped as to why it is shutting down. It would make seance if it was drawing 5 amps or something.The circuit will stay running only if you current limit at half a amp but it will only output 4.5 volts but the input will be puled down to 9. something because of the limiting.I down think having removed the failed transistors for the 7 volt rail would cause this.There are 2 IC's that look to be running the show but I cant seem to find the right data sheet the first main one is 3375 E10735 M76 and the other is 2903 5g1 JRCThanks for any help
DC/DC unknown - Page 1
Forum section: electronics / repair

author: salviador
author_rank: Regular Contributor
timestamp: October 17, 2020, 10:02:02 am
content: What is this module? , still a DC / DC, does anyone know from the fragmentary abbreviation to go back to a datasheet?

author: shakalnokturn
author_rank: Super Contributor
timestamp: October 17, 2020, 01:30:38 pm
content: Yes looks like a dual output DC/DC converter.Not much hope with any references, maybe it has a part number printed on the hidden side?What equipment is it in?

author: salviador
author_rank: Regular Contributor
timestamp: October 17, 2020, 02:22:34 pm
content: is one of the control units of a hybrid car, in the diagnosis from an error in the DC / DC module in this control unitI try to take it apart hoping there is a clue in the hidden part

author: salviador
author_rank: Regular Contributor
timestamp: October 19, 2020, 10:37:06 am
content: scraping I found the code must be from the MURATA , it looks like an MPD0D003.But there is nothing on the net with this code, do you have any ideas?
dcs -8200 rtc issues - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: January 11, 2022, 03:08:48 pm
content: Hi all,this is a bit of a long story,a few years ago i brought a kenwood dcs-8200 dso untested from ebay,it worked ok except showed a low batt msg,i t wouldnt hold the time settings on the clock when power cycled,not an issue but it bugged me,after some looking around i found the battery for the epson rtc flat,i replaced this with a battery holder and fitted a cr 3032 i think it was 3v coin cell,still didnt fix the clock issue,next i renewed a disc ceramic cap and electrolytic cap+ the xtal in the circuit,after studying the schematic,at the time i had a user manual that had the schematics,this was 3 or 4 years ago,ive since lost the manual that i downloaded !,in the meantime,it worked ok after about 2yrs the issue is back,does anyone know where i can download the manual so i can fix it,or any ideas what to do?,it doesent afect the operation of the scope just niggles me,TIA m3vuv. p.s i assumed the cell was low low but still measured 3v,i replaced this with a Lithium-thionyl chloride cell but no luck.

author: coromonadalix
author_rank: Super Contributor
timestamp: January 11, 2022, 03:30:06 pm
content: a thread herehttps://www.eevblog.com/forum/beginners/my-new-scope/

author: m3vuv
author_rank: Super Contributor
timestamp: January 11, 2022, 04:04:04 pm
content: sorry to say but i was the op on the thread linked,thanks anyway.

author: m3vuv
author_rank: Super Contributor
timestamp: January 11, 2022, 04:06:22 pm
content: dont think i ever found a service manual as such,must of been getting mixed up,or at least for free,lots of spam adds tho with a google search!!
De-5000 LCR issues with larger capacitors - Page 1
Forum section: electronics / repair

author: chromguy
author_rank: Newbie
timestamp: February 25, 2020, 02:38:04 pm
content: I have a DER EE DE-5000 and has been working great for years except with high capacity caps basically larger than 1uF. At first, 1kHz was cranky and would not lock on to a value and keep switching back from Cp to Cs like it was hunting. After a while it would only work at 100/120 HZ, Now it will not work at all. I did take it apart and cleaned the board with IPA but it did not help.At this point it will not calibrate and get stuck at 00 on the short circuit stage. I have tried multiple probes and even bare wire. Funny a bare wire between +/ - the unit switches back and forth between Cp and Cs.I did notice that all solder joint look very crystalline but perhaps that is the lead free solder they used. I was thinking of reflowing as my last attempt.I did check google for repair information but not luck with anything useful.I am thinking "I need another Timmy"Suggestions welcome

author: usadave
author_rank: Newbie
timestamp: April 03, 2020, 01:04:24 am
content: I have had similar problems. It seems to read everything in capacitance quite low. It won't lock on to series and some of the button's don't work at times. I went to Amazon to read some of the current reviews and it seems the thing works great for 6 months to a year and then falls apart.... so disappointed as it got many good reviews on Youtube from many reliable people... trying to find a schematic here on eevblog but no luck so far... thx, Dave T

author: coromonadalix
author_rank: Super Contributor
timestamp: April 03, 2020, 07:59:15 am
content: For the calibration you have an english manual floating on the web, you have the open and short calibration mode, they have a 30 second timer when you do it, you have to do it all the way to get a good calibration, if you move or open or short the "wires" you'll have to redo it again ..I did get a new de-5000 and wanted to push it against my sencore lc102 for the large caps ex: 12000 uf and up, but with the covid-19 thing, i did not had the chance to do soMaybe the rubber key pad is not good enough for the mode(s) ??They are based on 2 chips design, and i did not saw any leaked schematics.
De-bugging PCB having power ground short  - Page 1
Forum section: electronics / repair

author: joniengr081
author_rank: Regular Contributor
timestamp: October 16, 2023, 10:20:15 am
content: Hi, we are having some problem with a Microcontroller based PCB having a single power supply +5 V that is supplied by a DC-DC converter on the PCB. How to de-bug if there is power and ground short. There are several components that use the same power and ground and I have no idea how to start de-bugging. Which components to de-solder first in order to trace the problem.

author: langwadt
author_rank: Super Contributor
timestamp: October 16, 2023, 11:48:37 am
content: Quote from: joniengr081 on October 16, 2023, 10:20:15 ampower it up, use thermal camera or alcohol to see what gets hot

author: Gyro
author_rank: Super Contributor
timestamp: October 16, 2023, 12:45:08 pm
content: This question comes up a lot, a forum search will bring up lots of threads which may save you some time in waiting for answers.For those not blessed with thermal cameras, and in the case of a hard short, those that are, the simplest and safest way is to use a low voltage current limited power supply and DMM. Set your bench PSU to maybe 1V and set the current limit to 1A. Connect the PSU across +5V and ground (as close to the DC-DC converter as possible. Then go around the board with a DMM, set to it's most sensitive mV range, measuring the voltage across the active and passive components (start with the capacitors) that are attached to the +5V rail. The lower the reading, the closer you are to the short.Do not share either supply lead with the meter leads, use both meter probes at each component. This will give you best location accuracy. With a 1A current limited supply, even a 3 1/2 digit 200mV range will give you 100u Ohm resolution. Turn off the PSU before clearing the fault to avoid any possibility on nasty transients.

author: joniengr081
author_rank: Regular Contributor
timestamp: October 16, 2023, 01:15:44 pm
content: Thank you very much for your comments. These tips are very useful.

author: mikeselectricstuff
author_rank: Super Contributor
timestamp: October 16, 2023, 01:20:27 pm
content: If you don't have a thermal camera you can use the "Rossmann method" - put some alcohol on the board and look for where it evaporates first.
de-soldering dead SMD caps in TV. - Page 1
Forum section: electronics / repair

author: josh132
author_rank: Contributor
timestamp: March 21, 2021, 09:00:40 pm
content: So i have a TV that was brought in to fix. The screen was fine the power supply wasn't dead. All seemed to be fine except for the Chinese caps which have clearly leaked and blown. I replaced them but i'm having trouble de-soldering the SMD caps. When ever I try to de-solder them, I keep ripping the pads off. Also it is very important that these caps get replaced because they are apart of the screen display system. So is there a way to remove them with out removing the pads as well? I searched all over the internet and methods used such as the long heat method don't work.

author: drussell
author_rank: Super Contributor
timestamp: March 21, 2021, 09:05:36 pm
content: If you're talking about the typical small surface-mount electrolytics, often with the little plastic "base" on them, it is actually often easier to just grab them with a pair of pliers and twist while pushing them down towards the board, which usually breaks the legs off the capacitor, leaving the trace intact.You then can just desolder the little piece of leg from each pad and it ends up actually being easier on the board itself than burning it up trying to desolder the capacitor whole.

author: perieanuo
author_rank: Frequent Contributor
timestamp: March 22, 2021, 08:58:34 am
content: hotair gun, anyway you throw the removed cap to the binthe solder with 'classic' soldering iron the new oneany 'mechanical' procedure will rip off the tracks on cheaper pcb'sor buy pliers for your soldering station for smd's

author: mariush
author_rank: Super Contributor
timestamp: March 22, 2021, 11:05:35 am
content: The video above has good advice.Same method is shown in this video from 10:30 onwards :Light pressure on the capacitor, twist gently and the leads will fatigue.

author: Shock
author_rank: Super Contributor
timestamp: March 22, 2021, 02:14:01 pm
content: Proper technique shown in this first video, you can use two irons to get reflow on both legs at the same time. If you only have one iron by reflowing with low melt solder you can extend the molten time and go back and forwards a few times before removal.The trick is to use flux and slighty wet tip to aid reflow. Hot air can also be used if you are careful not to damage or push around other components. You will want to wear glasses as heating up caps can cause them to explode.I've included the video for resoldering them. If you have the space on the PCB use the method shown at 5:23, it's the cleanest. He had a little too much solder on the pad. Use flux, a tiny amount would have prevented the problem on the second pin. .
Dead ASUS DUAL GTX 1070 GPU - Page 1
Forum section: electronics / repair

author: iRonNuke
author_rank: Newbie
timestamp: February 15, 2020, 02:26:09 pm
content: Repairing a ASUS DUAL GTX 1070 GPU.I bought a dead GPU. Its fans are spinning and white LED are lit, but not detected in Windows. GPU core is not getting warm (every component on the card is in room temperature).Noticed this (see pics) when I looked at it in a microscope. What's the missing component? May I replace it with a simular one, if yes, what component? Some capacitor?I have access to heated solder station.Thanks for any reply!

author: iRonNuke
author_rank: Newbie
timestamp: February 15, 2020, 02:27:33 pm
content: Pic whole backside of the PCB. Note the red marked area, is zoomed in in the first two pictures above.

author: ogden
author_rank: Super Contributor
timestamp: February 15, 2020, 03:25:16 pm
content: Most likely capacitor, similar to two other caps next to IC.

author: iRonNuke
author_rank: Newbie
timestamp: February 15, 2020, 05:55:56 pm
content: Okey, that seems right. But how do I know what kind of capacitor it should be?

author: ogden
author_rank: Super Contributor
timestamp: February 15, 2020, 10:26:28 pm
content: Quote from: iRonNuke on February 15, 2020, 05:55:56 pmUsually you read schematics. Other option - find datasheet of IC in question and check typical application circuit. It is ceramic MLCC capacitor, 16V to be on safe side. Capacitance - who knows, in range 0.1uF up-to 22uF or so. I bet that lack of capacitor is not reason why GPU do not work. It looks like pads are gone

author: Rasz
author_rank: Super Contributor
timestamp: February 16, 2020, 03:44:15 pm
content: this pair of resistors sure looks like some voltage feedback circuit

author: NiHaoMike
author_rank: Super Contributor
timestamp: February 16, 2020, 04:09:00 pm
content: Looks like someone tried to hack it to overclock higher by boosting the voltage.

author: wraper
author_rank: Unknown
timestamp: February 23, 2020, 04:48:32 am
content: Part broken off is 0805 capacitor. Also it was torn off together with pads and there are remains of traces on both sides. So repair will require bodge wires. Later I'll post a photo and desolder it and measure capacitance since I have a scrap board of this model.

author: sd
author_rank: Unknown
timestamp: February 23, 2020, 07:20:15 pm
content: That IC does current sensing.http://www.ti.com/product/INA3221Missing part is definetly a cap.

author: wraper
author_rank: Unknown
timestamp: February 24, 2020, 12:39:50 pm
content: It's 0805 10uF ceramic capacitor. You also need to restore traces like on attached picture.
Dead Behringer V-Verb Pro  - Page 1
Forum section: electronics / repair

author: Peacefrog
author_rank: Contributor
timestamp: June 02, 2020, 07:32:45 am
content: Plugged this in for the first time in years and... nothing - no LED illuminate, and the display is dead.Opening the box up, I removed the glue (as noted on other forums) and reseated the cables, but this didn't help either. The caps aren't bulging, but my meter (it was late, so I didn't pull out the scope) indicates that what I think should be the DC input to the 5V regulator is oscillating. There's an SMPS in there - I presume the logical step is to recap and see if this resolves the issue?
Dead corsair k70 keyboard - Page 1
Forum section: electronics / repair

author: LV
author_rank: Newbie
timestamp: March 07, 2021, 08:23:17 pm
content: Hello, i have a undetected corsair k70 keyboard which i am trying to repair but i can't find the issue all solder joints are good +5v goes to all the chips.I don't really now where to look at now." alt="" class="bbc_img" />

author: HobGoblyn
author_rank: Unknown
timestamp: March 07, 2021, 10:56:10 pm
content: Did you try resetting before taking apart?Unplug from PC, hold escape down, while still holding esc plug keyboard back in.About 5 seconds after plugging back in, release escape key and it should spring back into life (might have to try two or three times).I use mine (K63 but reset method is the same) wired on PC and Bluetooth elsewhere, quite often if I’ve been using it in Bluetooth mode, the PC won’t recognise it until I reset it.

author: LV
author_rank: Newbie
timestamp: March 08, 2021, 08:38:56 am
content: I've tried it many timesthe keyboard is drawing 28mA which doesn't seems rights

author: zzattack
author_rank: Regular Contributor
timestamp: March 08, 2021, 03:00:18 pm
content: Why not? Have you reloaded the firmware on it? Can you get it into bootloader?

author: LV
author_rank: Newbie
timestamp: March 08, 2021, 03:56:53 pm
content: you're right 28mA may be fine since the leds are off.I don't know how i could do that
Dead Dell Desktop motherboards - Page 1
Forum section: electronics / repair

author: guyman70718
author_rank: Newbie
timestamp: September 30, 2020, 10:14:04 pm
content: Hey there, I was wondering if anyone here could help me with 2 dell motherboards with the same symptoms that I have now collecting dust. Basically, I used to use a Dell Inspiron 3647 as a server and I had a kit of 16gb of ram from crucial installed. A few months ago, I realized that the thing was shut off for some reason, and I went to turn it on. Pressing the power button would make it come on for a second then go off. Replaced the power supply and same issue. I just declared it dead and sacrificed it for parts, as I had another dell I could use. I put the ram into a Dell 660s I had laying around and set it up, and it was working fine for about a day, when that PC shut off and started doing the exact same thing. Replaced PSU, reset CMOS and nothing changed. I tried resetting the CMOS on the original 3647 and now the power light doesn't come on at all when I press it, and no fan spin either. If I press the power supply self test button the cpu fan spins up to max speed and that's the only life I can get from the pc. I do have one more PC that I am now using as the server, but not with that ram anymore (duh) but now I am interested in trying to repair at least one of the motherboards as board repair practice.I do have a little SMD soldering experience, for example the third dell needed its BIOS chip replaced, but I don't know where to start to try diagnosing the board. I checked the caps and none are leaking or bulging as far as I can tell (both boards are about only 5 years old anyway), and that's really all I know how to do. I don't need to be spoonfed the answer, but it seems that most desktop motherboards aren't worth repairing to most people, so as a result there isn't much information on where to start. If anyone has any ideas, I am interested in hearing them.

author: guyman70718
author_rank: Newbie
timestamp: October 01, 2020, 07:01:14 pm
content: So, I made a little progress today looking at one of the computers. I checked the capacitors around the SuperIO chip for shorts and found none. I also checked around the chipset for shorts and found a few, but then I checked the working board and I also found a few so I'm just going to assume that my multimeter just isn't sensitive enough. (it is a fluke 73 series ii) I held down the power supply's self test button to see if it made any chips heat up and I found the chipset started getting pretty warm when I was pressing it, so I am starting to wonder if the chipset is bad (and this is a lost cause).
DEAD FLUKE 115 - Page 1
Forum section: electronics / repair

author: rvalente
author_rank: Frequent Contributor
timestamp: October 12, 2022, 06:59:30 pm
content: Hello Mates,I've been given this Fluke 115, board code FLUKE-117-3001 - REV 009The board is cosmetically very clean, someone touched the Q10 R20 and Q9, not sure if these are the correct parts.The meter draws 8mA when powered with 9V. No display or bip in any range sometimes a quiet buzzer noise.I do not know the meter historicC20 with is near U3 (LDO) measures 4.99VC25 the microprocessor cap measures 2.52VI tried to find some schematic but obviously they're not available.Greetings from Brazil!

author: rvalente
author_rank: Frequent Contributor
timestamp: October 18, 2022, 06:38:44 pm
content: Does anyone has a hint on the AD Converter marked LTFLK2

author: Eugenelag43
author_rank: Newbie
timestamp: August 23, 2025, 01:16:45 am
content: Hello sir i have fluke 117 not powering on,there is a missing part of the board because it was burned ,the ic in U3 on board,i will indicate the picture of missing ic and can you give me the exact model number of that ic,thank you in advance
dead fnirsi usb meter need help - Page 1
Forum section: electronics / repair

author: sx57
author_rank: Contributor
timestamp: January 10, 2025, 02:34:00 pm
content: hello everyonmy usb meter FNB 58 is dead and i need your help to see if i can repair it.it was connected to a high quality but fake samsung 45w charger and there was multiple short circuits. i involuntarily short circuited the charger and the tester was connected to it turning on and off because the charger protection was working. i realized my mistake and stopped .meter was working then but after a few hours of rest, when i tried to use the meter it was completely dead. i think probabley it was heated during short circuits and after a few hours of not working, it went to the next world. i don't know for sure though.my frined opended it for me.there is a component which gets hot when we connect the meter to a power source, I attached a pic of the component.it is a very expensive device in my country and i had the device only for one month.please help me if possoble.thanks

author: Swake
author_rank: Frequent Contributor
timestamp: January 11, 2025, 03:26:02 pm
content: If it heats up it might be dead or the consequence of something else failing.What is the marking on that chip?The first line looks like MJ4The second line is much more difficult to read 8J3, or 3J8?, orMaybe with light shining from another angle it is easier to readWhat is that chip connected to, what is the function of that chip?Have you asked FNRSI for help?
Dead HP 6632B - Page 1
Forum section: electronics / repair

author: ndp
author_rank: Newbie
timestamp: October 28, 2020, 12:04:01 am
content: Hi all,I purchased two HP system DC power supplies (a 6632A and a 6632B) at my local electronics surplus place. Paid $20USD for them as they were both marked "no display, no output".Upon inspection, both units were set to use 240V operating voltage. On the 6632A I just moved the internal switches to 120V, and it fired right up. No problems at all.The 6632B has proven to be more of a challenge. I changed the transformer wiring as stated in the service manual to 120V. Now when I switch on I get a low-level transformer hum, but nothing else. No display, no output, etc.The service manual isn't too helpful for this specific issue - in fact, I can't even seem to find the first test point it refers to. Could anyone advise on the first place to start checking voltages etc? Everything on the boards looks perfect, no sign of blown tantalum caps or the like.Thanks in advance.

author: TERRA Operative
author_rank: Super Contributor
timestamp: October 28, 2020, 01:11:22 am
content: I'd check the transformer isn't faulty first. Do you get any voltage out of the transformer, and are any rectifiers testing ok (not shorted)?Google will have the specifics of testing transformers.

author: Dr. Frank
author_rank: Super Contributor
timestamp: October 28, 2020, 08:28:29 am
content: Hello,obviously you already read my repair report about the blown tantalum capacitors:https://www.eevblog.com/forum/repair/agilent-6632b-fault-repair-and-several-design-flaws/This defect might not be so obvious on first sight, so I recommend to first check the voltages at the fuses, as indicated.The +/-15V supply and +5V also feeds the analogue side of the controller PCB, so that's the 2nd item to check.Nearly everything is inside the service manual, apart from the controller PCB.As there is no display, the '+ 5V interface bias supply' to this controller PCB should be checked.This might also feed the display PCB.Frank

author: jchw4
author_rank: Regular Contributor
timestamp: October 28, 2020, 09:18:17 am
content: Check that VFD is not broken.Unfortunately most of the units with "no display" actually mean "broken VFD". And display is unobtainable.
Dead intel NUC (nuc5i5RYB): Help me identify component - Page 1
Forum section: electronics / repair

author: dschie
author_rank: Newbie
timestamp: March 14, 2024, 10:02:09 am
content: Hey there, i tried to start my nuc (from 2015) that i last used about 3 month ago, but no reaction. Seems like it died unnoticed, and one component is obviously damaged. It looks like a transistor, but no way to tell what it was (labeling died with the component). Any idea how to find out what it was? i'm aware that the blown transistor might just be the symptom and not the original problem, but i think its worth a try. Not sure if relevant, but: there is a "power present" led on the board (which you cant see when it is in the case) that lights up, and the "charching"/yellow usb socket delivers power. appaerantly nuc5i5RYB is the board, nuc5i5RYH would be my NUC (with 2.5 bay), but the same board is also in the nuc5i5RYK (slim) NUC
Dead Nixie tube - Page 1
Forum section: electronics / repair

author: SYJON
author_rank: Newbie
timestamp: March 16, 2021, 12:21:24 pm
content: Hi! Today I recieved 8 Dolam LC-531 nixies. Unfortunately one of them dont light up at all. Can anyone suggest how to diagnose/repair this tube? Grid looks like a bit oxidized, I removed some of oxidation from the leads but still no life signs

author: SYJON
author_rank: Newbie
timestamp: March 16, 2021, 01:15:10 pm
content: Update: supplying it with higher voltage makes cathodes glow violet...

author: TheMG
author_rank: Frequent Contributor
timestamp: March 16, 2021, 01:26:03 pm
content: Seal has failed (probably around one of the pins) and air has gotten into it.Unfortunately, there's nothing you can do about it. It's dead.
dead philips pm3262 scope - Page 1
Forum section: electronics / repair

author: m3vuv
author_rank: Super Contributor
timestamp: April 19, 2022, 06:13:42 am
content: I have a dead pm 3262 scope,seems theres no eht,so far i saw an arc on the underside of the eht unit,i dremmeled out the burnt potting from the arc area and resealed it,when i first got the scope,on pwer on the red power led would come on for about a second then go out,if i cycled the power strait after it wouldnt come on but would if left for a few mins,now after resealing the eht unit i get a solid power led and the screen illumination works,also i notice the neon in the focus unit illuminates ,any ideas what to check?,i can only measure 3kv with my test gear,tia Paul.

author: Alex_Baker
author_rank: Frequent Contributor
timestamp: April 19, 2022, 03:37:22 pm
content: I would start by checking all the other power supply voltages. Perhaps one of them died when the HV shorted.

author: m3vuv
author_rank: Super Contributor
timestamp: April 19, 2022, 07:03:43 pm
content: would the eht arcing over to ground kill a power rail?,im in hospital tomorow so will try and power the psu pcb with it removed from the scope,its impossible to probe with it fitted in the scope,will look as soon as i am home from my op.
Dead power supply - help locating small smd datasheets - Page 1
Forum section: electronics / repair

author: LiftedTrace
author_rank: Regular Contributor
timestamp: July 01, 2025, 01:04:04 am
content: Im trying to repair a power supply and i cannot locate what these chips are. (See attached)I dont know how to find things this small with virtually no info on them.Can anyone lend a hand?Thanks.

author: amyk
author_rank: Super Contributor
timestamp: July 01, 2025, 03:00:46 am
content: PUMD9TL431CDBPS2561ICE1PCS01These were dead easy. Just search for the marking and the package type.

author: Harry_22
author_rank: Frequent Contributor
timestamp: July 01, 2025, 02:42:50 pm
content: Hi LiftedTrace!What are you going to do next?

author: fzabkar
author_rank: Super Contributor
timestamp: July 01, 2025, 04:15:01 pm
content: http://markingcodes.com/search/c/2561http://markingcodes.com/search/c/dt9http://markingcodes.com/search/c/t3cshttps://www.google.com/search?imgtype=photo&q=1PCS01&tbs=isch%3A1%2Cisz%3Am&udm=2https://www.google.com/search?imgtype=photo&q=t3cs%20sot23-6&tbs=isch%3A1%2Cisz%3Am&udm=2https://www.aliexpress.com/w/wholesale-dt9.html?initiative_id=

author: LiftedTrace
author_rank: Regular Contributor
timestamp: July 01, 2025, 07:06:15 pm
content: Quote from: Harry_22 on July 01, 2025, 02:42:50 pmI suppose I'm going to make some links for identifying package types so I can start searching like a pro.

author: Harry_22
author_rank: Frequent Contributor
timestamp: July 01, 2025, 09:02:12 pm
content: I guess you should check for the high tension first.ICE1PCS01 is PFC controller that provides around 390 VDC on the biggest capacitor.

author: LiftedTrace
author_rank: Regular Contributor
timestamp: July 06, 2025, 12:31:50 am
content: Im actually not even getting any power to this chip.

author: Harry_22
author_rank: Frequent Contributor
timestamp: July 06, 2025, 03:39:39 pm
content: Detailed PCB photos may help.

author: MathWizard
author_rank: Super Contributor
timestamp: July 07, 2025, 04:44:03 pm
content: Is the PCB from a Toshiba TDP MT200 projector ? Where does the low voltage supply for the controller IC come from, is that voltage there somewhere, or also missing?

author: LiftedTrace
author_rank: Regular Contributor
timestamp: July 28, 2025, 08:27:39 am
content: Sorry for late reply, im not receiving alerts from replys.I actually started a new post about the power supply itself:https://www.eevblog.com/forum/repair/optoma-ep716-projector-no-power/msg5975083/#msg5975083I figured it was a separate issue from trying to locate smd datasheets.Ive pretty much given up on it, so if anyone can lend a hand it would be great.
Dead PSU from a 1996 Power Macintosh - Page 1
Forum section: electronics / repair

author: joelgraff
author_rank: Contributor
timestamp: January 21, 2022, 01:58:36 pm
content: Hello,I've been trying to sort out a dead PSU on a 1996 Power Macintosh. The board is typical for a Mac - there's a side for the logic board (with 5 / 12v power rails) and a side to power the CRT (left and right sides respectively in the marked up image). The CRT is not powering up and I see maybe +2V on one +5v rail for the logic side. I see line voltage to the line filter caps and nothing thereafter.I pulled the line filter caps and tested them - they look perfect. The fuse is not blown. So right now, I'm thinking it's likely on the hot side of the PSU (since both the logic and CRT outputs are dead) and it's probably not a transistor because of the intact fuse.Obviously, I'm not much of a power supply person, so I'm looking for tips or ideas on how to go about diagnosing this a little more efficiently than just pulling diodes and caps to test them...

author: BrokenYugo
author_rank: Super Contributor
timestamp: January 23, 2022, 07:22:45 pm
content: Mains filter caps are usually the last to die, if your problem is a cap it's probably one of the little ones on the hot side involved in some standby or bootstrap supply.

author: Gyro
author_rank: Super Contributor
timestamp: January 23, 2022, 07:49:33 pm
content: That black rectangular Sincera part is a thermistor (puck type held by spring contacts inside the enclosure). It's a possible candidate for going high resistance.Edit: It might be related to the CRT degaussing coil, I can't tell from its position.

author: Labrat101
author_rank: Unknown
timestamp: January 23, 2022, 07:58:25 pm
content: Did you check the PFC coil . They fail or have a broken terminal .

author: Gyro
author_rank: Super Contributor
timestamp: January 23, 2022, 08:00:21 pm
content: Does it have PFC?

author: Labrat101
author_rank: Unknown
timestamp: January 23, 2022, 08:17:48 pm
content: I think its the vertical board that sitting behind the large power caps .I could be wrong . I don't have a schematic of that psu on hand .EDIT .. Some serial No., Model numbers . type . would help track down a schematic .

author: joelgraff
author_rank: Contributor
timestamp: January 24, 2022, 10:10:32 pm
content: It's a Power Macintosh Performa 5260. The PSU board model is PWB-1801.I did find a link to the service manual:https://www.ordinosaures-parc.org/images/PDF/apple/Mac/powermac.perf_5260.5280.pdf
Dead Tektronix TDS3034 (solved) - Page 1
Forum section: electronics / repair

author: John.S
author_rank: Contributor
timestamp: June 08, 2019, 02:49:15 pm
content: Yesterday I grabbed my scope to do some measurement on my Modbus Arduino project.Put in the power cord, push the start button and……. nothing happened.First challenge, how to open this puppy.Well..... YouTube is your friend, after 2 videos that shows absolutly nothing, I found one that explains everything, how can you even design something like thatSo, after removing the housing it is all nice and well reachable.First remove the part with the fan, pre power supply and regulator board with only three screws.Then seperate the pre regulator board.The service manual says that you can power up the pre regulator, and it should give you 15 Volts DC.So I did that, and it gives me absolutely nothing. I was happy with that, it seems to me the easiest part of this scope to repair.Fuse was OK, and little over 400V DC on the main capacitor, so no worries there. Main switching mosfet also looks OK.Also no leaking or bulged capacitors so no obvious culprits on the board.Becouse the amount of components is not that much I started poking around with the ohm meter to check for shorts or open circuits.I was lucky, one of the first things I measured was the 2 resistors in series at the place of R2 (2 x 390kohm in series)One of these 2 was open circuit !!I did not have resistors of this size in my parts box, but decided to put 3 270kohm resistors in series and solder them in for testing.I conncted the power leads back an and put 230Vac on the board and got 15 Vdc on pin 1 and 6 on the connector. So its alive againPut everything back together, and powered the scope op, and luckily it is up and running again.I did order new resistors of the right value and size, when in I will change my bodge resistors for the new ones.So at the end it is a verry simple repair, but becouse there is not so much to vind about these scopes i post it anyway.Mayby it can help other people.GreetingsJohn.

author: Jay_Diddy_B
author_rank: Super Contributor
timestamp: June 08, 2019, 03:20:06 pm
content: Hi,If you want to know more about this power supply, including a partial schematic, look here:Link:https://www.eevblog.com/forum/repair/a-tektronix-tds3014b-with-two-strange-issues/msg991612/#msg991612I have seen this fault before.Regards,Jay_Diddy_B

author: John.S
author_rank: Contributor
timestamp: June 08, 2019, 04:46:42 pm
content: Hi,Thanks for the link.It is now obvious why the supply was completely dead with R2 open circuit.With this fault it is also clear why nothing else is damaged.greetingsJohn.

author: Kibabalu
author_rank: Regular Contributor
timestamp: November 05, 2020, 05:52:32 pm
content: Quote from: John.S on June 08, 2019, 02:49:15 pmThank a lot to you John. I faced the same issue like you on a TDS3034. Due to your post I found the fault very fast: One of the two R2 resistors was broken. Also thanks to Jay_Diddy_B for the background information. You two saved money for me resp. my company.
Dead Tivo - Unknown power supply driver - Page 1
Forum section: electronics / repair

author: LiftedTrace
author_rank: Regular Contributor
timestamp: June 03, 2025, 12:43:43 am
content: I got this dead tivo.Checking memory voltages, i find i am missing 2.5v.Tracked 2.5v back to two power supply coils that share a common chip that i am unable to find a data sheet for. (See attached pic).This may or may not be dead, but i dont know wjere else to go until i can see if this chip is working or not.Any one got an idea what this is and what pins supply it? Its the "B3385" chip.Thanks!.

author: fzabkar
author_rank: Super Contributor
timestamp: June 03, 2025, 02:10:27 am
content: LTC3850https://www.analog.com/media/en/technical-documentation/data-sheets/LTC3850-3850-1.pdf

author: LiftedTrace
author_rank: Regular Contributor
timestamp: June 03, 2025, 02:18:47 am
content: Awesome!Thank you.Seems i got power to it, but nothing coming out.Need to study it a bit and see if something else it wrong or if this chip is dead.Thank you for the link!.

author: LiftedTrace
author_rank: Regular Contributor
timestamp: June 09, 2025, 10:44:54 pm
content: Any tivo gurus out there?The chip that @fzabcar found was the issue i had with my 2.5v and 1.2v power supplies.This thing now seems to boot. For a breif time i get a booting screen on a computer monitor hdmi, but onna tv its always black.Soon as it passes the booting screen its black.Tried changing the format to every option it had with no screen output. Unfortunately i have no composite inputs to try.I can hear the harddrive clicking happily away as if the unit is working fine, just dead video.Im wondering if something in the main chip died and took out the chip i just replaced.Does anyone know if there may be log files or something on the HD i can access and see if there are hardware failures or something, or maybe a way to ssh onto the box through ethernet and view logs?Thanks.

author: fzabkar
author_rank: Super Contributor
timestamp: June 10, 2025, 12:32:36 am
content: Could 2.5V and 1.2V be the Vio and Vcore supplies for the MCU/SoC?

author: LiftedTrace
author_rank: Regular Contributor
timestamp: June 10, 2025, 01:25:47 am
content: Im not really sure what those are.But i know the memory was the 2.5v and i traced the 1.2 to a via under the main cpu chip with the large heat sink.Hdmi traces also goto this large chip with heatsink.
dead yamaha rxv491d please,please,please help  - Page 1
Forum section: electronics / repair

author: craigtasker34
author_rank: Newbie
timestamp: May 24, 2020, 09:58:12 am
content: hi bought yamaha rxv491d off ebay description was no powerupon removing cover found D12 near hdmi port blown (small hole in it) and ic1(hdmi chip) shortedfitted new D12 and hdmi chipchecked voltages i have 5.5v and +3.3m present but have no standby led and key combination on front of receiver of (tone+info+power) gives me nothingon connector cb23 i havepin 1 =+3.3m = 3.305vpin 2 = dgndpin 3 = acpwrdet = 3.276vpin 4 = pry =0vpin 5 = dest = 2.719vreplaced main microcontroller thinking that too had been damaged but still same function/readingsany ideas why pry would be 0v ?any help would be greatly appreciatedregardscraig
Dealing with shattered cell phone glass - Page 1
Forum section: electronics / repair

author: Peabody
author_rank: Super Contributor
timestamp: June 08, 2021, 08:52:49 pm
content: My Moto G6 fell from a good height to concrete below, and the front glass is shattered. I guess the front glass is tempered since it seems to have released *ALL* of its stored energy into a massive spider web that covers the whole screen.I have a new phone coming from Motorola (Lenovo has a 10% veterans discount) but the old one seems to still work perfectly as far as I can tell, so I'd like to repair it if possible, and keep it as a backup, or maybe use it as a wifi tablet.I understand I have two options. I can replace just the front glass for about $13 or I can replace the entire glass, digitizer and LCD screen module for about $26. Of course that's with my labor. From what I've seen online, the big problem with replacing just the glass is getting the old glass unstuck from the digitizer. Apparently the glue they used there was never intended to be unstuck. I dont have a heat gun, just a hair dryer, and there's one video that says a hair dryer isn't enough. So pretty much all the videos on Youtube are about replacing the whole LCD module. But I don't know if there's a visible difference in quality between the original Moto LCD, which still works fine, and the 'generic' replacement.Anyway, I just wondered if anyone here has done this kind of repair and might have some advice about what to do, and what to look out for. So far I've successfully removed the back cover of the phone, using a hair dryer, which wasn't that difficult.I found several videos about using various fillers to repair the broken glass itself - nail polish, epoxy, windshield repair compound, etc., but in all cases the phones still looked like crap afterward. So as far as I can tell that just doesn't work, which is too bad.

author: mr.fabe
author_rank: Regular Contributor
timestamp: June 08, 2021, 11:50:32 pm
content: I would replace the entire display panel assembly (glass, digitizer and LCD screen module). Provided that you purchase the correct replacement panel, you will not notice any difference in the screen display quality. It will be difficult to separate the different layers and you will most likely end up purchasing the whole assembly later. You will need to use a heat gun to aid in loosening the screen adhesive. Using a hair dryer will take forever even if it is able to generate enough heat.

author: Koray
author_rank: Regular Contributor
timestamp: June 09, 2021, 05:59:03 am
content: That glue requires some special chemicals to clean. During the process it is very easy to damage the LCD. Once clean you have to use LOCA UV adhesive to combine the layers and it is best applied in a vacuum chamber to get the bubbles out. You will need plenty of UV, too. For home DIY people, the best option is to use complete/finished LCD/digitiser assemblies.Good luck.K.

author: Peabody
author_rank: Super Contributor
timestamp: June 09, 2021, 02:23:24 pm
content: Thanks for the advice. I will order the complete LCD assembly.
Debugging an ATX power supply. - Page 1
Forum section: electronics / repair

author: westfw
author_rank: Super Contributor
timestamp: August 31, 2020, 11:30:13 pm
content: I have an ATX power supply that has gone "wonky." The computer it powers will run for about 5 minutes when first turned on, and then goes into a loop where it powers down and starts up again, not quite lasting long enough to boot.It seems like it's likely to be a classic "bad capacitor" problem. (replacing the Supply fixed the computer that it was in.)Any hints on how I can narrow that down to WHICH capacitors I should try to replace? Unfortunately, there isn't any obvious bulging or leaking.

author: bob91343
author_rank: Super Contributor
timestamp: September 01, 2020, 12:38:27 am
content: Schematic diagrams are available online.

author: darkstar49
author_rank: Frequent Contributor
timestamp: September 01, 2020, 11:16:30 am
content: facing similar issue with an oscilloscope power supply (other thread...), but if it uns for 5+ minutes first, I'd rather suspect a thermal-related issue.If I got it right, when you let it cool down, you're good for another 5 minutes, correct ??If yes, I'd be really surprised if one of the electrolytics was the problem... keep us posted !!

author: PKTKS
author_rank: Super Contributor
timestamp: September 01, 2020, 02:50:42 pm
content: Most of the time a generic rule of thumb in these cases...- If one capacitor is already presenting problems (dry.. heat.. bad manuf.)=> replace them ALL or just in case ALL from same brand or model- The ALL case is not cheap - the cheapest thing to do is replace ONLY ONE- If ONE CAPACITOR is faulty you may have luck to spot them visuallyOR... by using LCR techniques in which removing them (and discharging)for testing is the best method.I my personal opinion if would remove anything ... I rather replace it.Paul

author: westfw
author_rank: Super Contributor
timestamp: September 02, 2020, 12:28:39 am
content: QuoteYep. Could still be the caps, though. I haven't quite decided that it's worth fiddling with; after all, new computer ATX power supplies are very cheap...

author: Haenk
author_rank: Super Contributor
timestamp: September 02, 2020, 07:05:36 am
content: The ATX supplies are really cheap nowadays, buying a working used one is probably aven cheaper. Even cheaper than the replacement partsAnd don't use it with your computer, when the PSU starts to act up, evil things like voltage spikes might happen. Which are obviously not a good thing for sensitve computer parts.