ATX PSU 5V STANDBY OK, OUTPUT VOLTAGES LOW

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ATX PSU 5V STANDBY OK, OUTPUT VOLTAGES LOW - FIXED! LER

Рет қаралды 10,282

Күн бұрын

Learn Electronics Repair #109
ATX PSU - 5V Standby OK, Output Voltages Low
This is the third and final part of this repair and I'm happy to say it is now fixed
So what was causing the problem and what can we learn from this?
Want to find out? You just gotta press PLAY
Parts 1 & 2 of this repair are here: You really need to watch part 2 at least before watching this one.
PART 1: • ATX PSU 5V STANDBY OK ...
PART 2: • ATX PSU All Output Vol...
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Пікірлер: 31

@InfoDav 3 жыл бұрын

Yes, I'm a software engineer, and you are totally right. Sometimes I can struggle all day to find the solution to a bug, I go to sleep and I wake up with the solution. It's funny how the brain works.

@ratbag359 3 жыл бұрын

I learnt the hard way I was trying to power a system with heavy loads on the 12v rail and I knew the psu worked fine on the older system. Back then I was not aware of how they regulated the 3 rails off one switching transformer and the key is they don't In this case the supply relies on a load on the 3.3 I have no idea why they did not include a base load on the 3.3 rail many manufactures always ensure the minium load is present on all rails even though it is wasted energy and some like to put the load resistor against the output caps. This is where the newer supply's have a advantage one 12v rail and buck converters for all other rails. 3.3 sata is often not used by many devices most use local regulation for any voltage other than 12v and 5v. It's just like the -12 -5 volt rails they are only a gesture now days as modern rs232 transceivers make their own + - rails If the atx connector has a sense wire in this case 3.3 some supplies have it on the 5v rail are a sign that they have a preference for load on that rail.

@LearnElectronicsRepair 3 жыл бұрын

Hi Josh Knowledge is good but you proved experience is king. As I mentioned in the video this is a Compaq PSU, so I figured that the designers knew exactly what equipment it was intended to be used in and did not put any resistive load on the 3.3V for that reason. Like you, I also learned the hard way on this one - and I feel that sharing the experience is a very good way to help others. This is why I publish videos that don't always turn out the way I would wish. Welcome to the channel, I hope you stick around and throw in your two penny worth (now that's an old English expression!) when needed. Cheers mate!

@ratbag359 3 жыл бұрын

@@LearnElectronicsRepair i forgot to add this supply regulates both 3.3 and 12 v rails but with to little load on the 3.3 output it does as you decribed.

@rgry 2 күн бұрын

Thank you for all your repair video. Great knowledge from your many years of experience. I wonder if you would comment on a problem I have with at PSU. The voltage is correct until I put a little load on it, then it get very unstable and lower voltage. Could you give som hint or points to another video of yours that handles that problem?

@peddersoldchap 2 жыл бұрын

Hello Richard. Thank you for putting the links to the other parts of this repair in the description. Tchau!

@jamesdecross1035 3 ай бұрын

Really interesting. I'm currently analysing a problem that may not exist, too. I have an ancient AT-style power supply from a Compaq. I can't get the 5vdc rail to go high.

@intrax2tv 2 жыл бұрын

I fixed my bestec atx-250 12z from a compaq machine today and your video's were really helpfull. So thank you very much! 12v rail was collapsing. Caps were ok, but I suspected one optocoupler, so took it out and measured, seemed fine and put it back. Than the psu started working again. I can't seem to find a pwm chip in this one. Strange! Thanks again...

@amirvafa7344 Күн бұрын

Thank u u r a great engineer I have a problem with an atx which its green wire ps on voltage is 4volt but the ic supply 5volt ref correctly psu starts but only 12volt rail has low voltage 11volt .and also drops to 10volt under load condition. I didn't find what was the problem with th gren wire

@jonka1 2 жыл бұрын

It just shows how easy it can be to get lost down a hole looking harder and harder for nothing. Kudos to you for being so up-front about learning. Are you now going to make a fixed load to add on to power supplies on all 3 rails in line with the connection to your tester? That way you eliminate that situation.

@daz41262010 Жыл бұрын

great explanation and yeah I also wake up through the night with not just answers to repairs but answers to solvable parts of some games (adventures) or RPG games :)

@shokdj1 7 ай бұрын

Yeah I code and often wake up with a eureka moment not just with coding but other things as well all great and nerdy lol

@andymouse 2 жыл бұрын

Very valuable indeed, great tutorial! and yes I have found on to many times to count occasions that walking away from a problem is the quickest way to solve it, just change of scenery a meal or whatever and bingo !....cheers.

@Adrian_Finn 3 жыл бұрын

Thank you for these vids and josh as well, I feel like I have learned some valuable stuff here, Brilliant.

@LearnElectronicsRepair 3 жыл бұрын

@ Adrian Thank you so much. Josh, if you find yourself in Gran Canaria sometime let's have a beer or three :-)

@grahambambrook313 Жыл бұрын

Many a 'genius' has said the same, Faraday and Edison included. It seems to be related to an Alfa wave state in the brain when fully relaxed, which could be why I seldom get it!!! 🤣

@dennismatro593 2 жыл бұрын

11.7 volts?? instead of 12volts output? why? is that the normal voltage of 12 volts?

@BreakTheRules2011 3 жыл бұрын

Cracking job 😁

@darshanags Ай бұрын

Did you do a fox video for #8 PSU on the hall of shame list? I couldn’t find the video.

@davidhollfelder9940 Жыл бұрын

Oh yea! Spontaneous delayed recall/moment is my go to 😮

@gasparreis303 3 ай бұрын

I bought a Nox Urano II 630w atx power supply, but it never turns off, with the fan always running without being connected to any motherboard, I checked with the ohmmeter that the green PowerOn wire is in a short circuit with the black wires? How can I solve this problem ?

@cajuncoinhunter Жыл бұрын

The KIA 431 I have is testing Black lead on Cathode , red lead on Anode 570 mV Red lead on Reference 751 mV on my DMM , but when I put it on my component tester like your LCR T4 it shows defective or unknown part.... Is that normal readings on the Tester or is my DMM showing a good part ?? I'm not familiar with the 431 , Didn't have those in 2 way radio in the 80's and 90 s ... Thanks Mon Ami .....

@InfoDav 3 жыл бұрын

Still was very insightful.

@LearnElectronicsRepair 3 жыл бұрын

Yes, and a little frustrating LOL

@KB1UIF 2 жыл бұрын

Hi Rich, the video was great, thank you, I've learned something about these computer power supplies that I wasn't aware of, as in loading all of the output rails !! Would it be possible to increase your Audio on your future videos? I often need to crank it up for your Videos. Then when an ad comes on I get blasted out of my chair !! Thanks again.

@estartermanual Жыл бұрын

thanks for your contribution. Then the problem was "no load" on 3,3v... I have one ATX PSU that without load shows correct voltages but at 0.2A load in 12V rail, the voltage goes down until PSU restarts. And another one from an ancient Pentium 4 that basically have low voltages on start, at minimum load voltages crash down already. Any ideas?

@alimoradi2323 3 жыл бұрын

Good video

@LearnElectronicsRepair 3 жыл бұрын

Glad you enjoyed

@Iceking007 Жыл бұрын

But on low voltage you don't want it on, turning the led on turns the PWM off. So a low voltage isn't a bad thing, just the PWM should be turned on fully. Or am I missing something?!

@Iceking007 Жыл бұрын

I don't understand how the 3.3V keeps the other voltage low. If the 12V is low the PWM should be on, the Iso-Led should be off. This doesn't help me at all.

@amirvafa7344 Күн бұрын