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- Опубликовано: 15 сен 2024
- Learn Electronics Repair #057
ATX Power Supply - 5V Standby Voltage too Low
In this video we look at an ATX Power Supply that will not start up. We use datasheets to understand how the ATX Power Supply Works, then diagnose the cause of the fault
You can watch part 2 here
• ATX Power Supply 5V St...
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Thank you
Richard
Hello Richard!
I don't mind that your videos are long. It's better they are long and extensive, than short and "show-off-y" (some youtubers want to show that they know the terminology). So thanks once again for letting us, newbees in on understanding the world of electronic repairs.
Måns
Another Great video and believe me, they are never too long, just more to learn, the proper way! Thank you Richard!
58:07 I have the same ESR Meter and I tell you one tip - Those stock wires/leads/probes are wobbling in the sockets (which you can see on the video) and this makes a bad connection. When you push button to do a zero cross calibration (with shorted probes together) it MUST go to zero ohms at the end. If not then calibration will be bad. As I see on the video it wasn't zero ohms. You have to take out the probes from the socket and plug again and provide better short circuit on the probes/clips, and then try it again until you get 0.0000 and after that try to not provoke probes to wobble in the socket until you ger mesure resoult.
so...
What happened on your video is that you finish zero cross calibration at +0.030/0.010 ohm above normal, so the zero point was already shifted in memory. But when you took a capacitor to measure it, you move the probes/leads making wobble in the socket, so they catch better connection compared to the previous one. So you had less loss on the probes BUT the meter last calibration was +0.030/10 above normal so that is WHY you get negative reading on capacitor: minus -0.060. The reading will be fake, and you can wrong assume that capacitor is good because you will see lower value.
Those stock probes/leads, has the metal stripes on the plug which touch the socket inside. Take a tweezers and push back them, to make connection harder - this will eliminate the wobbling issue.
Thanks for the video, I wish more people did PSU repairs.
HI there Tech Cemetary- thanks for the thumbs up, I take that as a real compliment!! I certainly intend to do more PSU repairs. Did you watch my other ATX repair?
ruclips.net/video/f7NmQHH-xUg/видео.html
@@LearnElectronicsRepair I have not, but I'll remember to watch it later when I have a moment.
Good video. Normally all you get is replace blown cap. No investigations or explanations. Well done. I like in depth videos as a hobby guy.
I had a go at mending an ATX where a lot of caps had blown and it was so packed tight I gave up as I had another working one,did replace one cap using a pencil and blue tac,what a pain,thanks for the vid👍
Hey Richard
I have not watched the final video yet. I know that it was not worth fixing the PSU. But as a teaching would it of been best replace all the caps, Since those were all probably similar ageing and BAD.
Your channel popped up in my feed some of the early a videos are interesting and real life. I dont know where the location (i know you live in the Canary Islands) is all i gather is looks like you have a repair shop in the shopping district because occasional some people walk past the window and phone calls.
Keep up the good work
Kev
Do I see some “puffed” caps, some leaking out of the top? .. was wondering when you’d notice.
19:36 - Why the load here? I’ve watched several of your PSU repairs and nothing about a load was discussed (unless I have yet to watch that one). A DickyCAD would be helpful.
Thanks for the video, very intresting
My pleasure!
Thanks , here is part 2 ?
every part has a number near it e.g. c101 for cap just use the number don't need a picture
My guess this is exact the fault my PSU has, at the biginning the PSU fault was developing slowly like a miss to turn on sometimes but not always, sometimes did actually turn on and was working perfectly fine untill at the next day turn on, eventually after some days have pass the PSU definatly no longer turn on, my guess is like a capacitor becoming more and more day by day faulty
Hi Enrico
Also check out this video, if you did not already do so. In this case the 5V Standby was good and once again the problem was caused by capacitors, but not the ones on the output rails (3.3V, 5V, 12V). it is quite likely your power supply could have a problem similar to this one.
ruclips.net/video/byKn0ZR0OK4/видео.html
Thank you for the link, I am going to check carefully all your videos about computer power supply,
@@LearnElectronicsRepair I think the 5V Standby circuit is the reason for my PSU no longer working, or a bad capacitor somewhere belonging to the 5V Standby circuit which is the primary side, mothing to do with the (3.3V, 5V, 12V) output rails. Before becoming completely faulty, the PSU after struggling to turn on but thereafter the PSU was working perfectly fine until the next day when I was trying again to turn on, at some point the PSU was no longer able to turn on even if I was pushing again and again the turn on button
@@tonschk Hi Enrico, on the most recent repair I found that the 5V Standby was OK but the same transformer that generated 5V STB also generated a 24V supply (or was supposed to do) for the PWM controller and the transistors that provided drive to the main switching transistors (5V 12V 3,3V) Have a look if you have a similar circuit yourself - another winding/rectifier/electrolytic on 5VSB transformer.
I checked all the capacitors and replaced them
The vsb fault didnt change !
It gives me a steady 2.9v without ripples!
Hi Tech Eng, yeah I am waiting for the capacitors to arrive as I didn't have suitable replacements in stock.- I will upload another video once I change them regardless of whether it fixes the problem or not.
If you have watched some of my other videos then you will know I do 'reality' on this channel, so sometimes I can't fix things and sometimes I get it wrong and then upload another video explaining how and why I was wrong, and what the real problem was.
So I am not saying 100% changing the capacitors will fix the fault, but I am sure you will agree those old ones had to go before we can get any further! If that still gives low 5V STB then in the next video it will be diagnosed further.
Hi Tec Eng. I'm still waiting for the capacitors for my PSU, and it's not easy to diagnose your problem at a distance, but have a look for a small device that looks like a transistor, somewhere near the opto-isolator, that has the part number TL431 (or some other letters followed by 431). Although it looks like a transistor it isn't, it's a programmable zener didoe. This is the reference voltage that the feedback circuit uses to compare with the output voltage. If the reference voltage is wrong then the output voltage will be wrong. If your PSU has that part then change it and see if it fixes the problem.
The output voltage of the TL431 can be set by two resistors, one of the resistors could also have changed value causing this sort of fault. The datasheet is here, and the formula for calculating/checking the resistor values is on page 25 (if it is configured this way on your psu)
www.ti.com/lit/ds/symlink/tl431.pdf?ts=1623298969093&ref_url=https%253A%252F%252Fwww.google.com%252F
@@LearnElectronicsRepair
The tl431 is inside the chip in my circuit
The chip code is HS8108B
@@techeng3940 I will do my best to help everyone who posts here but as you can appreciate it is almost impossible for me to diagnose the fault on your PSU without having it on my workbench. Have you tried changing the HS8108B chip? I've just uploaded another video with a PSU that also has low 5V Standby but for a completely different reason. Check this one out as well. ruclips.net/video/Clim6i1hmmE/видео.html and it may be relevant to your fault.
Also if you are not already a member I suggest you join the free forum at www.badcaps.net/forum/ they have a section specifically for power supply repair and a lot of knowledgable guys there. You will find me there both asking questions and helping others, though I am more likely to be posting in the motherboards and graphics card section.
Actually @Tec Eng are you sure that HS8108B is even generating the 5VSTB? It seems to be far more sophisticated than it would need to be to do that and also the datasheet says it is for half bridge designs (ones with two transistors driving the primary of the transformer) so from that info I would say this is the PWM controller for the main power rails (3.3V, 5V, 12V) not the 5VSB. Without knowing the model of your PSU I can't say, but possibly it has a discrete transistor oscillator to generate 5VSB like the other video I linked above.
The best idea would be to join badcaps forum as I suggested, start a thread in the 'Troubleshooting Power Supplies' section
www.badcaps.net/forum/forumdisplay.php?f=32
Explain the fault, what you have tried so far and post some clear close up photos of your PSU showing the PCB from a few different angles and also state the make and model. Once you have done that reply back here and I can take a look at the pics and see if I can help you further, though I am sure others will probably do so before I get chance LOL
Man I love watching your videos but you thank you can stop saying yal so much.thank you
An interesting video, but I'm sorry to say, the quality of the recorded video was miserable to watch. It looks like you recorded it on an old Nokia.
Hi Tony
I was very much learning when I first started the channel as I had never done anything like this before. I had some settings wrong in OBS studio and the actual video resolution was bad, even though the files were 1080p.
I realised this after a while and sorted it out, or at least I think I did.
Considering I uploaded 35 videos in the first four weeks, the one you watched would have been about two months into the channels life.
Would you do me a favour check out some of my later videos and let me know if you are still getting very poor quality?
If you are then I need to look into this further. You can select 1080p in RUclips settings for my videos
Thanks
SIMPLE TO REPAIR BUY A NEW ONE CHEAPEST WAY TO REPAIR THEM WORKS ALL THE TIME 😊😊😊