500W ATX PSU 5V Standby OK but does not turn on - A more complex repair. LER

Learn Electronics Repair #088
500W ATX PSU has 5V Standby but does not power on
This is a more in-depth video into ATX PSU repair. The first thing to note is that this one has a different design to the others I have looked at on this channel.
The fault is more complex and requires a closer look at, and understanding of, the circuit. I make no apologies for the the length of this video but if you watch it through you will definitely learn more about power supply repair. So if you are serious about learning then you know what you need to do :-)
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Thank you
Richard

[@UpInSmoke54]

Take out your favorite alcoholic beverages and take a sip every time he says "YEA"! You'll be drunk in no time! 😂 Like your videos! 👍

[@jc1971]

Ye?! ❤

[@originaldanman]

Very in depth and overwhelming for a newbie like me. However I was very disappointed having watched the whole video and it still wasn't fixed though not a complete waste of time because I like doing this sort of thing, and you have to spend some time feeling like your spinning your wheels if you're ever going to learn anything. However, for the amount of time I spent watching this I could have made enough money to buy several power supplies, not including the time I've spent been fooling around with it trying to fix it. This video reminds me of all my failed attempts to try and fix one of these things since I have no instructional experience other than youtube.

[@blackterminal]

Im tired of throwing out power supplies. I wish more equipment was legally forced to be modular inside. I try my best to fix things though. Sometimes i can. I keep trying. Thanks for the video.

[@Lyndalewinder]

Such good instructional videos - you have a flair for this Richard!

[@johnprescott6614]

I was going to vote for this psu but forgot in the end.Really interesting video, thank you.

[@LearnElectronicsRepair]

Yeah it was a really interesting one. After I replaced those two capacitors the 8.7V rail went up to 23V - so I was correct in my guess that the 8.7V was too low to make the circuit work Feel free to vote for any of the other ones

[@garypoplin4599]

3:10 - The second time you powered on there was some audible interference in the sound of your video and (3:26) the fourth time a buzzing came through.

[@Dutch_off_grid_homesteading]

Heya, yes love those in dept vlog I'm learning so much from them it's just grazy how much thank you

[@skysurfhf]

Where is part 2 ? I Can't find ...

[@pablogiordano93]

kzbin.info/www/bejne/rXnZZGato8mBiqM

[@daz41262010]

love the fault searching for video :) awesome to watch :)

[@cysrandomthoughts1087]

Thank you for sharing your knowledge in these coool videos 👍

[@PSIHUNTER00]

Das Interview war gefühlt noch mühsamer als mit Frau Milborn. "Vor zehn Jahren haben sie im Park eine Ente schief angeschaut, meinen Sie das das ein Bundespräsident machen sollte und würden sie diese Ente heute füttern?" Aber super durchgekämpft! :D

[@jonathanrose456]

Provided the socket is double pole, I’d have left it connected for the safety ground.

[@michaelsimpson6603]

Great atx repair videos, would have particular interest in the FSP brand faults.

[@Backcountry_Bodger]

Hiya Dicky, again great video, 👍🏻 just wondering if you did manage to do the next repair on this particular PSU or was it a bust in the end and couldn't be fixed?

[@Bully000001]

Excellent videos as always. I have learnt a lot in a short time. Thanks. I am looking at a Atx power supply taken from an audio mixing desk. The outputs are not by cable but by pins. There are 48 pins in 3 rows of 16. The output pins push into 48 sockets on the mixing desk. I have 2 units one working and one not. The only outputs I can identify on the working supply are 2 5.4v supply rails and a number of earths. The working unit will not turn on out of the mixing desk and I am struggling to find out how it turns on. The Pwm chip is a tl3843p which does not have a start up pin. The chip is turned off by overvoltage at the current sense pin or the comp pin. Any ideas as to how I might turn it on?.

[@andreasmoll_0924]

"Whisper words of wisdom..say it to me...say it to me.."

[@Xorat]

Thank you for the video looking forward to part 2!

[@LearnElectronicsRepair]

You're welcome - it's a long one, but there is plenty to learn here. All the parts are ordered so it will just be a few weeks to wait until they arrive.

[@Keepitreal260]

Where can I find components would need? I have a transformer out of a gas range power supply. It is missing a peg, another isn’t soldered on, while a third looks like the solder is breaking.

[@davidhollfelder9940]

Did you try grounding the pin 4 of the optoisolator (maybe thru a resistor) see if PSU turns on? You’re brave and gutsy to try a fix these old SMPSs. I tried several years ago .. the chain reaction failure just went poof, all over again. Now, defective ones go e-waste, no debate! Hmm, W2F is this transistor?

[@wegi9621]

6:00 guessing is forward 2T with 2 clamp diodes. And high key is driving by single ended transformer as floating source.

[@jonathanrose456]

Is there value in repairing power supplies?

[@jturner7798]

Have you messed with any APU supplies for pc like ePower EP-450cd? I have a few of them and they work as intended, I have been fiddling with one in an attempt to bypass the need for an ATX supply to turn it on.

[@edwardotoole6736]

Great work, keep it up, you are a great inspiration to young electronic enthusiasts.

[@nesssilvano2226]

Good day from Philippines what is substitute of 500 w pc per supply regulator I doubt about it is transistor or scr

[@spaceted3977]

I've got a capacitor discharger, which looks like a small battery welder !!! I'm very wary of Capacitors !!!!!

[@eamonhannon1103]

When you a PSU that has a good +5Vsb but it shuts down after the green wire is shorted to the black wire , and the outputs start to turn on but then shut down ,then can we say there is a problem with one or more of the outputs and the supervisor circuit is shutting down the PSU OR there is some feedback regulation problem ? In this case can I disable the supervisor circuit without adverse consequences to force the PSU to turn on so I can trouble shoot the problem ? . I have a PSU that shuts down sometimes on power up . I tried connecting 6K8 sequentially the 3.3V and +5V outputs but this does not help . Can I force the PSU to turn on by disabling the voltage monitor circuit ? Any advice welcome

[@RyanUptonInnovator]

A great video.

[@mohammadrazmi9467]

where is the solution?i couldn't find it

[@jamesmackie6641]

What would you suggest the best way to buy components if your fixing ATX power supplies and 1500 watt and a 4000 watt inverters

[@samsami1130]

Thanks dear for this amazing video as always, btw .. you shorts the main capacitors with any 5 watt ceramic or cement resistor with 100ohm, i do it always, it saves your time... cheers 🍻...

[@mik13ST]

Would it make sense to bypass or temporarily remove the PFC for testing purposes in this case?

[@justinc9991]

Looking for part 2 but can’t find it?!?

[@chinnarao326]

Resp Sir! Very Excellent Class Sir. Sir Conon MF244dw Printer Power Supply DC Section 0.1Ohms 2Resistors was burned Sir and New Power FET K4005 was Replaced Sir and 2 Resistor Replaced with 1Ohms, 10 Ohms, 22 Ohms Resistors but again and again Burned Sir. and Series Lamp was a very Lettle Glowing Sir and Resistors Burned Sir. Where the Problem Sir. Very Hardly Searching Sir but not Solved Sir. Please Advise Sir. waiting for Ur Message Sir. --- Chinna Rao, Paderu, Visakhapatnam Dist, Andhra Pradesh.

[@pablogiordano93]

Hello mate, great videos I have watched a few, and I cant help myself from watching them from start to finish! I hope you can guide me a little, I have a 700 watt psu and the circuit is extremly similar to the one on this video. It also is giving 5 volt on standby and when I short the green and black wires the fan twitches for about a second (if conected to a motherboard, it also makes the cpu fan twitch for a second) also testing with a multimeter it gives voltaje on the yellow/red wires for 1 second but goes back to zero and wont give voltaje until I short the green wire again. Could you guide me into where you think the fault is? Thanks a lot. Also ps on is only reading 2.7 volts.

[@andrefff]

check all capacitors

[@sveniv1754]

Hello from Germany! I´ve got a Corsair HX750i which shows me a failing +12v Voltage on my ATX tester. Do you think it is repairable at all? I already got a new PSU but I liked my HX750i very much so I do not want to give up. I am absolutely not an electrical guy when it comes to electronic devices. Maybe I could ship it to you for making another KZbin Video and you could try to save my little baby? Kindest greetings from Germany - Sven

[@KaisUK]

where can i buy that 3.3kohm capacitor discharge he used.

[@orange_tweleve]

Pretty much any electronic hobby store. But I wonder how they would look at you if you ask for a single 3.3k ohm resister 😅

[@djbell9939]

Could u send me the schematic of your light bulb setup

[@tenminutetokyo2643]

The bodge wires were a trace/pad repair.

[@juliusvalentinas]

Is there part 2 video for this repair?

[@LearnElectronicsRepair]

I put this on one side and didn't get round to going back to it. The parts arrived ages ago, and I still have it so I'll try to do it this coming week

[@juliusvalentinas]

@@LearnElectronicsRepair Thank you for reply. looking forward to the repair. I have similar problem with one PSU

[@Iassonas65]

Is there a part 2 of this repair?

[@LearnElectronicsRepair]

I think I got distracted from this one. It's been lying on one side for a while - the parts are here. I'll try to get round to making part 2 this coming week

[@Iassonas65]

@@LearnElectronicsRepair I look for ward to it 👍

[@wegi9621]

A bulb 75W 230V AC is enought to fast discharge main cappacitor 200-450uF charged to 390V DC? Or bulb will be burn?

[@LearnElectronicsRepair]

Personally I would use a power resistor - around 2.2 K or so

[@wegi9621]

@@LearnElectronicsRepair just look at this discharge methods - incredible :] kzbin.info/www/bejne/bmPRaJWpYtydos0

[@peddersoldchap]

What's the wattage of the resistor used to discharge the main capacitor?

[@netten2057]

i use a 27ohms ceramic resistor , he used a 3.3k

[@davidut55]

Part 2 kzbin.info/www/bejne/rXnZZGato8mBiqM

[@Kepsizadam]

When will the solution video of this problem come?

[@LearnElectronicsRepair]

Tomorrow

[@notavailableforeveryone]

Could you use an RCD instead of a lightbulb?

[@LearnElectronicsRepair]

As a safety device yes, but the light bulb will protect devices in the PSU against further damage and also give a visual indication of what is going on

[@Iceking007]

Where is part 2???

[@mik13ST]

How does the single capacitor PSU work? I understood the half bridge design used in others but not this one. Given the schematic you draw around 30:40, the current still cannot flow through the primary winding because the one transistor is always closed (assuming the square wave drive signal is inverted for the other transistor). What am I missing? Why are there two transistors?

[@davidhollfelder9940]

Hmm, this video has low audio level .. we have to turn it up. When the ads come on, we get blasted!

[@blackterminal]

He would say. "OK yeah. Yeah. I'll note it yeah".

[@artineogda]

For discharge capacitor i use multimeter set to LoZ

[@Cendof]

Hi, thank you for these great videos! I watched almost all but still having problems with a Compaq PSU PDP-100 series, Part NO.: 386461-001, Spare NO.: 387672-001. It is a really strange one, with quite different 24 pinout, +5 V AUX and +3.3 V AUX present, but nothing can start it. Do you have maybe any suggestions? I did search google, but no proper solution.

[@Kepsizadam]

Is this device repaired now? I still do not understand? Where was the fault?

[@LearnElectronicsRepair]

Hi - it was waiting parts for a long time from Ali Express but they are all here now so I will make part 2 very soon and link it from this video

[@Kepsizadam]

@@LearnElectronicsRepair Thank you very much, I'm looking forward to the next videos from you. Greetings from Turkey.

[@marywrong7041]

Camera is in the wrong location. Suggestion is to move the camera away from you instead of straight down, or wear a head camera.

[@LearnElectronicsRepair]

@Mary Wrong This video is 7 months old - I have moved things around a bit since then - check out some of my more recent videos and see if you think they are better

[@thabed007]

EDIT: *WARNING* after being enlightened by the video's author i want to warn you that this will work only if the psu is in good condition! But even then. even if it was a brand new psu, ALWAYS make sure to check the caps with a multimeter afterward to make sure it worked, it only takes a second and could save your life, THE HIGH VOLTAGES COULD BE LETHAL!!! There's one thing that i'm surprised not that much peoples seems to know! there's an easy way to discharge those big caps quite quickly, simply ground the power on wire(green) for a few seconds after it's been unplugged from the ac(so long as there's nothing wrong with the power on path i guess)!! When it's still in a pc, you can even just hold the power button for a while! It will also discharge other small caps on the motherboard, and I always do that 2-3 times before opening a case when i need to work inside a pc, it reduce the risk of unwanted discharge/short between wrong pins when plugging/unplugging stuff if something is wrong somewhere! Been recommended to always do that as a teen when i first started to learn how to build/troubleshoot/repair computers by a guy that worked on pcs and other electronics all his life!! He also told me back then that it can also reduce the risks of static electricity, but since that for static it's your body acting kind of like a capacitor, i don't really see how it would work! But if true my only "theory" is that maybe having empty caps would make them able to absorb it if it's on the discharge path.. maybe?? But hey, the more you can augment your chances of things going right when working on something the better, been doing it ever since, and(touching wood) never had a problem of a discharges of any kind(static or otherwise) in the 20 or so years since i started!!! 😉🤓

[@LearnElectronicsRepair]

** IMPORTANT ** Do NOT trust this information ^^^^ to help you!!! Or even save your life! If you have a faulty ATX PSU, it is quite possible for the large capacitors to charge up (when the bridge rectifier is being supplied with AC the capacitors will quite happily charge up to 320V) but you can have a fualty power supply that presents NO LOAD to those capacitors - eg the PSU can not switch on, you have open circuit Mosfets, No 5V STB etc. So how can grounding the ATX 'power on' wire (green) possibly cause it to 'turn on 'and discharge the high voltage capacitors on a faulty power supply like this? The fact it is quite likely that the power supply can't possibly turn on and the current path that would normally discharge the high voltage capacitors is completely open circuit (due to a fault condition) so there is NO DISCHARGE CURRENT PATH! Honestly, I don't criticize anyone's opinion here (everyone is welcome to their own view on this channel and I do not delete comments even if I disagree with them) but what you are suggesting here is DOWN RIGHT DANGEROUS and I have to call you out for it. TO EVERYONE DO NOT TRUST YOUR LIFE TO WHAT THIS GUY IS TELLING YOU. IT IS WRONG. To sBeDs - please read carefully what I say for your own safety Copy Paste in case it was deleted as YT does sometimes outside of my control posted 1 hour ago ----------------- there's one thing that i'm surprised not that much peoples seems to know! there's an easy way to discharge those big caps quite quickly, simply ground the power on wire(green) for a few seconds after it's been unplugged from the ac(so long as there's nothing wrong with the power on path i guess)!! When it's still in a pc, you can even just hold the power button for a while! It will also discharge other small caps on the motherboard, and I always do that 2-3 times before opening a case when i need to work inside a pc, it reduce the risk of unwanted discharge/short between wrong pins when plugging/unplugging stuff if something is wrong somewhere! Been recommended to always do that as a teen when i first started to learn how to build/troubleshoot/repair computers by a guy that worked on pcs and other electronics all his life!! He also told me back then that it can also reduce the risks of static electricity, but since that for static it's your body acting kind of like a capacitor, i don't really see how it would work! But if true my only "theory" is that maybe having empty caps would make them able to absorb it if it's on the discharge path.. maybe?? But hey, the more you can augment your chances of things going right when working on something the better, been doing it ever since, and(touching wood) never had a problem of a discharges of any kind(static or otherwise) in the 20 or so years since i started!!! 😉🤓

[@thabed007]

@@LearnElectronicsRepair yeah i know not to trust this a 100%, when opening one i always put my multimeter on them to check and even keep it there while i ground the power on pin to to make sure i see the voltage drop if there's any!! Don't worry about me, i won't even touch the smallest caps without checking them first, i'm not interested in dying, and even just a small zap is almost "insulting" to me!! XD But thanks a lot for your reply and knowledge, Quite frankly i never opened a defective psu intending to try and repair it, i just used to have a box full off old obsolete one that i took apart back when i started to dabble in electronics to salvage everything on them!! XD I'll edit my previous comment not to precise that this will work if the psu is in good condition. Thanks again!! 😅

[@Kepsizadam]

lesson 2 problem fixed videos wait me :)

[@psnvprasad9654]

This much over length please reduce

[@LearnElectronicsRepair]

I have no control over how long it takes me to fix stuff! If you think you can do repairs to a set time frame then good luck to you. Eventually I think you will find out it does not work that way. Could take 10 minutes could take 4 hours or a couple of days - the whole point is getting there in the end.

[@steliosstamatopoulos-oh9vc]

😂

[@61spindrift]

Not possible I could listen to the way you talk in this video and finish watching it. I see many of your vids come up by youtube algo and I never watch them. Too bad for me I guess because it is exactly what I want to learn. But no way can I listen to them. My loss.

[@LearnElectronicsRepair]

Maybe you don't like the way native English speakers talk?

[@61spindrift]

@@LearnElectronicsRepair I guess I do not. Again, my loss as you obviously know electronics and it is what I am trying to learn.

[@cyborg6294]

@@61spindrift You can activate subtitles

[@61spindrift]

@@cyborg6294 activate subtitles? Will look into how, thanks.

[@61spindrift]

@@cyborg6294 Got it! Thanks and thanks for not posting something rude. I was honest about wanting to learn from an expert and I clearly could not understand his or really any "heavy" British accent. I did manage to figure out "subtitles", something I did not know about. Even at 65 I still learn something new everyday. This KZbin is mostly a younger persons platform and have just recently started to watch, learn and enjoy from it.