ATX Power Supply PSU Repair - DO THIS FIRST!

[@hullinstruments]

I’ve got at least 200 computer power supplies ranging from cheap ATX supplies like this, to the top of the line modern ATX supplies, server supplies ranging from 20 year old never used models… All the way up to UNBELIEVABLE power output with some of them weighing well over 100 pounds and being the size of a standard tower computer. All hot-swappable of course, you can see something like it on the “diode gone wild“ KZbin channel if you type in “server power supply”, he has two great videos where he goes over the design on the inside and kind of looks them over. He is such an incredible teacher when it comes to electronics. he had some massive server units that someone donated and I I have dozens of supplies like that, I don’t know why I’ve just heard them over the years when I see them cheap or free I grab them. Sometimes they’ve been swapped out but they still work, only swapped because they reach their expected life cycle in hours Wish you were somewhere in the United States I could send you a whole pallet of those bad boys. I don’t know why I’ve saved so many, but they do come in handy every now and then when you need parts or a very good quality supply for something in particular. Must be well over a ton of them. the incredible build quality with most of them and designing Quality is just insane. Most of the service supplies are super high-quality Delta and Hewlett-Packard branded stuff Those super high-end server power supplies from five, 10, and even 20 years ago… They’re just stunning on the inside. And capable of putting out absolutely insane levels of power.. I don’t remember the specs of all of them but not uncommon at all for them to put out dozens of amps on certain voltages, sometimes hundreds of amps, many of them ranging between 2.5 kW to 5 kW output. Just incredibly designed. I highly suggest checking out Diagon wilds to server power supply videos. They’re just really need to see the insides of, and if you check around locally you will definitely be able to find some because these big businesses and server rooms swap these things out regularly they don’t wait until they fail they swap them out after a certain amount of time.

[@steve6375]

I was a PC System Builder/Designer in the UK for many years. When picking an ATX PSU for a system, I obviously had to work out the maximum loads on each of the ATX output rails (depending on what might be fitted to each skew of a new PC mainboard). But it is more complicated than that. Some mainboards+CPUs+peripherals use very little current on certain voltage rails. It depends of what type of drive is fitted (2.5", 3.5", SSD, none, etc.) and what rails the mainboard uses (some would get 3.3V or lower voltages from the 5V rail, some from the 3.3V rail). Also some PSUs failed to regulate properly if there was not enough load on the 12V rail, some failed if not enough draw on the 5V rail, and some failed to regulate only if there was sufficient current draw on both 5V and 12V or 12V+3V or 12V+3V, etc. I always had to ask each PSU manufacturer for the minimum current specification for each rail (or combinations). Also, a power supply often could not supply enough power on one rail even though the total Watts output was far less than it's rating (because the Wattage rating assumes a certain 'mix' of current on each rail). Some PSUs even relied on the bulk capacitance in a mainboard for smoothing/regulation. I many cases we had to ask for slight tweaks to be made to a specific model of PSU so it would support a range of PCs skews and then we only took that specific bespoke variant from the manufacturer. I am still amazed that, even today, 95% of ATX PSU manufacturers do not specify minimum loads (even in their data sheets). Instead they prefer to put a note on certain PSU ranges that say 'not suitable for xxx types of system/CPU' when they find out it doesn't work properly for one of the reasons above!

[@dictator7586]

Thank you for giving another generation this amount of high quality knowledge we will use your videos to make earth a better place in future

[@LearnElectronicsRepair]

You are welcome, and everything that stays out of the landfill is a small victory for the environment.

[@jamesdecross1035]

This is really helpful. I need to go through this to get some older AT (not ATX) PSUs going again.

[@paulansette6145]

How is the light bulb safety wired?

[@godfree2canada]

coincidence I'm troubleshooting the same PS, it has a drooping 12 & 5 V rails, 5 will drop to 4.4, its seems to have will drop to have slow cycle that adjusts values

[@ratbag359]

I to have come across many power supplies with lables that state values that could never be supplied constantly by the components inside.

[@wilsard]

thanks for the tip on the monitoring wire. great info. no way those tiny diode rectifiers could take 400 watts either. i've never seen a 4 pin molex on a sata drive either. i guess it was really early and power supplies didn't commonly have sata power yet. i've still got old hard drives like the ones you used, that i've had since new. i use them for data and OS backups. all linux.

[@berndp3426]

Those slowly-failing lowESR caps are a silent dreaded snake over time. Which strikes suddenly at some point.

[@ondrejbursa9969]

I also have a HDD from 2008 that has SATA and molex, and it was quite useful when I added another disk to the PC and there wasn't any more SATA powers, so I used that molex :-)

[@LearnElectronicsRepair]

Yeah I guess it is just one of those oddities, like LGA775 motherboards with both AGP and PCIe. Nice to see you made good use of it, keep hold of it too, unusual retro PC hardware prices are only headed in one direction ,and it's ^^^^^^^^^

[@johnprescott6614]

Psu No 3 (the 80+ one) looks interesting but I can't remember if you have fixed it (I could check but the last psu marathon has fried my brain). Seriously now, thanks for all your amazing videos. It does take time for me to go through everything but it is well worth it.

[@LearnElectronicsRepair]

Ho John, Number 3 is fixed kzbin.info/www/bejne/bH-ymKWdlpqrZpY The remaining ones are No 2 - 300W - 12V high, 5V low No 5 - 250W - 5V & 3.3V unstable No 6 - 400W - Dead No 7 - ???W - 5V Standby Unstable No 8 - 300W - powers on and straight back off again No 9 - 350W - No Output No 10 - 400W - 5V Unstable No 13 - 450W - ??? Mystery Fault ??? No 15 - 450W -5V Standby Unstable Plus there are a few still In progress waiting parts It is possible some of the above just need to be run under load (see I also learn while doing this) - I will go back and recheck them to find the genuine faulty ones and update the list I've also been learning while working through this lot

[@johnprescott6614]

@@LearnElectronicsRepair No 8, No 7 (or 15) and No 6, whichever you fancy doing, for the variety of symptoms they have.

[@ondrejbursa9969]

What do you think about power supply that doesn't turn on, but the standby cycles on an off every half of second. I can see some bulged capacitors, so I will replace them, but do you think that will solve the problem or there will be something else?

[@LearnElectronicsRepair]

Well basically you just have to replace the bulged capacitors first and then see what happens. Also check for small capacitors near the 5V Standby transformer Check out this video if you didn't already watch it - this could possibly help you a lot kzbin.info/www/bejne/eZ3Ti5qBe9CNkKc

[@jonchapman6821]

9:17 that’s normal, it’s just an early (transitional) SATA drive as you said.

[@bitsnbobs1969]

love your videos i started buying faulty power supplys sell on due price incress in uk just wondering how you distarge large cappasitors

[@LearnElectronicsRepair]

Use a power resistor - I have shown this on some of my videos - I used something like a 2.2K 5W resistor which I was holding with a pair of pliers. Good luck with your scrap power supplies - I hope you fix some of them :D

[@bitsnbobs1969]

@@LearnElectronicsRepair thank you i went to scrap metal yard got 5w resistor out microwave solderd 2 wires to legs and works very well no more electric shocks lol

[@LearnElectronicsRepair]

@@bitsnbobs1969 Excellent. Do you know the ohms value of the resistor? Stay safe :D

[@notavailableforeveryone]

I have this ATX PSU which had blown capacitors. They were Fuhjyyu and after checking the translation, I am suspecting someone must had picked that name for fun. Funny trivia aside, got the capacitors replaced with new ones, PSU works fine when on, but is a very interesting one. As soon as you plug it in both fans and their LEDs come on. After inspection, they are powered from a Fan PCB which seems to have 3 inputs, 5VSTB, GND and 12V. 12V is only 12V when fully on (on PSU tester), otherwise it's 3.6V. The fans are 12VDC 3.6W. It's not exactly great setup because it draws 10W doing nothing and spinning fans. So I just wanted to ask if it makes sense to either unplug that PCB from 5VSTB altogether or hook it with the 5V output rail so the fans come on with the PSU? Thank you.

[@LearnElectronicsRepair]

Hi KS OK so if the fans consume 3.6W (each) and are 12V fans then Watts = volts x amps so 3.6W = 12V x amps so current = 0.3A = 300mA If there are 3 fans then in this PSU then yes that is about 10W (10.8W by my guess-timation) but that does not seem like a lot for high airflow fans - if this PSU has three of them With that amount of cooling required then I assume this PSU is a high powered one If the fans would even work on a 3.6V supply, the resistance of the load should stay the same (unless they use some fancy internal boost converter on the fan PCB to increase the voltage back to 12V or some other clever trickery) so if R stays the same then we have R = V/I = 12 volt /0.3 amps = 40 ohms If V is reduced to 3.6V then I = V/R = 3.6V/40ohms = 0.09A = 90mA So wattage at 3.6V (and presumably a slowly rotating fan) W=VxI = 3.6Vx0.09A = 0.32W per fan = 0.96W total IMHO if that was the way the designer made the PSU I would leave it how it is - in a PC, plus or minus 10 watts is neither here nor there really. I did say I wouldn't do maths on this channel but that doesn't mean I can't do it :D Well at least on a Friday evening after a couple or three beers :D :D BTW also find I can speak a lot more Spanish after a few beers as well. Mas Cerveza Mas Habla Espanol. I was hopeless with foreign language (French as it happens) at school. Then when I was 19 I went on my first holiday abroad with some friends (strangely enough Spanish Costa Brava) and there I met a delightful young French girl name Veronique, who was also on holiday and spoke almost no English. In two weeks she taught me LOADS. She I even taught me to speak a few words in French as well!!! LOL (this is a true story) BTW What does Fuhjyyu translate too?

[@notavailableforeveryone]

@@LearnElectronicsRepair Thank you for the response. I must have been tired or something when thinking about making changes to that PSU, turns out if you leave it switched off it for 3 minutes without unplugging, it will turn the fans off completely. So it is a feature of the power supply, probably to help it cool down. I would never know if I didn't find auction for same PSU on ebay - it has that 3 minute interval listed in bullet points. Lucky me. I have never seen anything like it, but you always learn something new. I got this PSU - it is Global Win SAF520, from someone who said it was broken and it burned his GPU, but I think it must have been bad GPU. Before I replaced bulged and leaked caps, PSU would power up so it was never really broken. Now it is almost fully fixed. I am saying "almost", because when you leave it plugged after switching off, it starts making noises like "coil whine" or "capacitor discharging". It's not immediately after 3 mins and need to wait little bit longer. On the other hand when you totally unplug it, discharge is very fast. I put my retro rig on it yesterday and it works ok and is stable. All the other caps are flat, so I doubt replacing them makes any sense at the moment. Video here: kzbin.info/www/bejne/sHOUeIppfrV7sKM - i left it on standby after power off, you can hear the noise until i turn the switch off. If you have any idea what could that be, that'd be awesome. The PSU is 52A rated on 5V, so it's precious for my Athlon XP build. Update - just turned the retro PC on - it took few seconds after button press to actually come on (i had to press it twice or three times) and for first few minutes PSU gives some screeching noises. I am thinking screeching might be because other caps are dry but it's not visible and maybe NTC resistor needs replacing because it doesn't come on immediately, maybe it needs more time to heat up? Video with the screeching noises - kzbin.info/www/bejne/aJiVf4B-Z9agjck. For a fact - it is not the hard drive. I would think it's the large caps, but I replaced them with Nichicon as you can see. Urban dictionary has a translation for Fuhjyyu - www.urbandictionary.com/define.php?term=Fuhjyyu so you can have a laugh.

[@notavailableforeveryone]

There is a better video of the noise which I think is coming from the PSU. kzbin.info/www/bejne/o4XaepmngZuEi7c - I suspect it could be these large Nichicon capacitors that I fitted. They are new and they looked legit. On the other hand they are from aliexpress and could be counterfeit or just old. Cannot imagine anything else making that noise. And it is not the hard drive although it sounds like one. The noise goes away after 30seconds or so and I will need to investigate it further.

[@jasondoesthings919]

The work you do and the level of your knowledge is incredible. I have been sharing you channel everywhere I can. Thank you for sharing your wealth of knowledge.

[@LearnElectronicsRepair]

Thanks for sharing. Awesome.