oh my ...even if you did find the right caps I would seriously consider not plugging anything important into this.

It looks like pure chinesium with a sprinkling of backyard electrical engineering, the top right back of the board is a mess, top left looks suspect too .. board could use some ultrasonic cleaning.

Everybody Chyang Fun tonight...

Suggestion: The 3 larger ones (12mm?) -> 2200µF, 16V the 2 smaller ones (10mm?) -> 1000µF, 16V

And some good cleaning is recommended.

🤣 maybe i should just give up on this Chyang Fun engineering masterpiece 😀 case is rusty too. it just the AT power supplies don't come by easily so i thought maybe i should fix it and learn something along the way too.

when i got the PC and plugged it in, first there was two bangs, followed by sparks from the HDD end 12V molex connector and then there was smoke from molex and the PSU itself and then burning smell from the PSU before going quite (seriously all these happened) so this PSU is not just any old power supply it is a diva demanding attention and care 🤣

jokes aside I will not plug this into anything until I am 100% sure of it

so I guess i should order x3 2200µF, 16V the x2 1000µF, 16V from Chyang Fun website if i can find it on Google! i like the caps to be OEM original hehe

behshad wrote on 2024-04-20, 09:58:

LOL maybe i should just give up on this Chyang Fun engineering masterpiece :) case is rusty too. it just the AT power supplie […]
Show full quote

🤣 maybe i should just give up on this Chyang Fun engineering masterpiece 😀 case is rusty too. it just the AT power supplies don't come by easily so i thought maybe i should fix it and learn something along the way too.

when i got the PC and plugged it in, first there was two bangs, followed by sparks from the HDD end 12V molex connector and then there was smoke from molex and the PSU itself and then burning smell from the PSU before going quite (seriously all these happened) so this PSU is not just any old power supply it is a diva demanding attention and care 🤣

jokes aside I will not plug this into anything until I am 100% sure of it

so I guess i should order x3 2200µF, 16V the x2 1000µF, 16V from Chyang Fun website if i can find it on Google! i like the caps to be OEM original

Some guys just want to watch the world burn 🤣.

I think it would be easier to get an adapter that allows an ATX PSU to be used as an AT one, you wont have -5v but unless you are working with really early sound cards I doubt itll be an issue.

https://www.ebay.com/itm/155425481556 Something like this for instance which comes with either an ATX switch or an AT switch, I use these with a cheap 300 watt ATX PSU that has molex, they work just fine. I find it to be safer going this path with valuable older hardware others here like their period correct AT power supplies so to each their own.

https://github.com/necroware/voltage-blaster you can then use one of these to get -5v if you need it, these two items combined are likely to be cheaper than fixing that PSU. (Pretty sure you can find these on Evilbay if you dont want to make it)

*I have no affiliation with the seller above

behshad wrote on 2024-04-20, 09:14:

is there any chance that I could know (or guess) the value of the caps so replacements can be ordered?

Give me a day or two and I should be able to trace it out from the pictures you provided.
Good thing you didn't remove the small caps by the TL494 controller too - those would have been a nightmare to figure out just from pictures.

Trashbytes wrote on 2024-04-20, 09:31:

It looks like pure chinesium with a sprinkling of backyard electrical engineering, the top right back of the board is a mess, top left looks suspect too .. board could use some ultrasonic cleaning.

Not sure how you came up with that conclusion... but if you don't have experience with power supplies, then I can understand.

If anything, the PSU shown here is actually built pretty well for an AT PSU. The primary switching BJTs are in TO-3P case (probably 2SC2526), which is clue #1 the manufacturer wasn't cutting corners. These can be pushed up to 350 Watts in some designs. Main transformer is nice and large too. And on the secondary heatsink, there's another T0-3P part (likely the 5V rectifier), which again means the manufacturer wasn't cutting corners. And the -5V rail is derived from the -12V rail via 7905 regulator, which is nice to see.

Only thing I will nick on is that the primary side EMI/RFI filter appears to be using regular metal film (PP/PE?) caps instead of proper X2-safety -rated caps. Likewise, the "Y2" caps appear to be standard 1kV ceramics. But that's not a huge issue at all.

All in all, the PSU should be able to do the rated power on its label based on the parts I see inside.

behshad wrote on 2024-04-20, 09:58:

when i got the PC and plugged it in, first there was two bangs, followed by sparks from the HDD end 12V molex connector and then there was smoke from molex and the PSU itself and then burning smell from the PSU before going quite (seriously all these happened) so this PSU is not just any old power supply it is a diva demanding attention and care 🤣

If that's truly the case, then the PSU might be in for more than just new caps.
Can't say anything more from the pictures provided, but if the fuse is blown, it will definitely be in for an overhaul.
The good news is that parts for these PSUs are readily available and they are not too hard to troubleshoot if you have *some* experience with using a multimeter to measure/check parts. Of course, whether or not that's worth doing is a totally different argument.

Trashbytes wrote on 2024-04-20, 10:10:

I think it would be easier to get an adapter that allows an ATX PSU to be used as an AT one, you wont have -5v but unless you are working with really early sound cards I doubt itll be an issue.

+1
That's usually (if not always) the easiest solution if AT PSUs are not readily available in one's location.
Back when I lived in the USA though, there were plenty of AT PSUs readily available on eBay.
On that note, always look for Astec AT PSUs - they are built like tanks and always used good quality Japanese caps. So the chances of these being bad or dying in a shower of sparks are slim to none. I had an Astec XT PSU built in the mid 80's. Figured it would die as soon as I powered it up, given that I picked it up for free from a person on Craigslist and that it had sat unused for at least 20 years (and 10 more in storage with me.) Contrary to my expectations, the PSU worked absolutely fine on the first go. I tested it with a proper load and it was still fine.

Trashbytes wrote on 2024-04-20, 10:10:

I use these with a cheap 300 watt ATX PSU that has molex, they work just fine. I find it to be safer going this path with valuable older hardware others here like their period correct AT power supplies so to each their own.

Be careful with the cheap / gutless wonder 200/300/400/xxx Watts PSUs that weight less than a baloon... especially the newer ones, which are often old designs "hacked up" for newer hardware by over-winding the transformer / O/P inductor on the 12V rail to keep it in spec under load. Such PSUs do very very poorly with a heavy(er) 5V load from an old system.

momaka wrote on 2024-04-20, 13:29:

Give me a day or two and I should be able to trace it out from the pictures you provided. Good thing you didn't remove the small […]
Show full quote

behshad wrote on 2024-04-20, 09:14:

is there any chance that I could know (or guess) the value of the caps so replacements can be ordered?

Give me a day or two and I should be able to trace it out from the pictures you provided.
Good thing you didn't remove the small caps by the TL494 controller too - those would have been a nightmare to figure out just from pictures.

Trashbytes wrote on 2024-04-20, 09:31:

It looks like pure chinesium with a sprinkling of backyard electrical engineering, the top right back of the board is a mess, top left looks suspect too .. board could use some ultrasonic cleaning.

Not sure how you came up with that conclusion... but if you don't have experience with power supplies, then I can understand.

If anything, the PSU shown here is actually built pretty well for an AT PSU. The primary switching BJTs are in TO-3P case (probably 2SC2526), which is clue #1 the manufacturer wasn't cutting corners. These can be pushed up to 350 Watts in some designs. Main transformer is nice and large too. And on the secondary heatsink, there's another T0-3P part (likely the 5V rectifier), which again means the manufacturer wasn't cutting corners. And the -5V rail is derived from the -12V rail via 7905 regulator, which is nice to see.

Only thing I will nick on is that the primary side EMI/RFI filter appears to be using regular metal film (PP/PE?) caps instead of proper X2-safety -rated caps. Likewise, the "Y2" caps appear to be standard 1kV ceramics. But that's not a huge issue at all.

All in all, the PSU should be able to do the rated power on its label based on the parts I see inside.

behshad wrote on 2024-04-20, 09:58:

when i got the PC and plugged it in, first there was two bangs, followed by sparks from the HDD end 12V molex connector and then there was smoke from molex and the PSU itself and then burning smell from the PSU before going quite (seriously all these happened) so this PSU is not just any old power supply it is a diva demanding attention and care 🤣

If that's truly the case, then the PSU might be in for more than just new caps.
Can't say anything more from the pictures provided, but if the fuse is blown, it will definitely be in for an overhaul.
The good news is that parts for these PSUs are readily available and they are not too hard to troubleshoot if you have *some* experience with using a multimeter to measure/check parts. Of course, whether or not that's worth doing is a totally different argument.

Trashbytes wrote on 2024-04-20, 10:10:

I think it would be easier to get an adapter that allows an ATX PSU to be used as an AT one, you wont have -5v but unless you are working with really early sound cards I doubt itll be an issue.

+1
That's usually (if not always) the easiest solution if AT PSUs are not readily available in one's location.
Back when I lived in the USA though, there were plenty of AT PSUs readily available on eBay.
On that note, always look for Astec AT PSUs - they are built like tanks and always used good quality Japanese caps. So the chances of these being bad or dying in a shower of sparks are slim to none. I had an Astec XT PSU built in the mid 80's. Figured it would die as soon as I powered it up, given that I picked it up for free from a person on Craigslist and that it had sat unused for at least 20 years (and 10 more in storage with me.) Contrary to my expectations, the PSU worked absolutely fine on the first go. I tested it with a proper load and it was still fine.

Trashbytes wrote on 2024-04-20, 10:10:

I use these with a cheap 300 watt ATX PSU that has molex, they work just fine. I find it to be safer going this path with valuable older hardware others here like their period correct AT power supplies so to each their own.

Be careful with the cheap / gutless wonder 200/300/400/xxx Watts PSUs that weight less than a baloon... especially the newer ones, which are often old designs "hacked up" for newer hardware by over-winding the transformer / O/P inductor on the 12V rail to keep it in spec under load. Such PSUs do very very poorly with a heavy(er) 5V load from an old system.

Cheap as in good quality ones from a reputable fab except gigabyte, I usually run Seasonic or one of their known off brands they use for their cheaper models, Corsair also make good cheaper models. I always avoid the chinesium ones which claim 600 watts but weigh less than a sheet of paper, I still have nightmares of SHAW PSUs from back in the day that made such claims and then promptly took your entire system with them the moment you loaded them up.

Super Flower is also another one I use they make very solid units. (EVGA uses Super Flower units so you could grab either and not go wrong here)

I concur with momaka on this one - the unit looks solid enough, and that's coming from someone who has recapped two AT units so far.
The first one I have is slightly thinner on the sinks than behshad's unit. No biggie as it was rated for @ 200W if I recall correctly.
The other one however, is a DEER branded unit that in no way known in this universe it will attain more than @ 150-180W without self immolating.

As for behshad's unit... looking at the label I think I've seen that particular style before, and chances are they just rebranded a Seventeam PSU.

PcBytes wrote on 2024-04-20, 14:00:

I concur with momaka on this one - the unit looks solid enough, and that's coming from someone who has recapped two AT units so […]
Show full quote

I concur with momaka on this one - the unit looks solid enough, and that's coming from someone who has recapped two AT units so far.
The first one I have is slightly thinner on the sinks than behshad's unit. No biggie as it was rated for @ 200W if I recall correctly.
The other one however, is a DEER branded unit that in no way known in this universe it will attain more than @ 150-180W without self immolating.

As for behshad's unit... looking at the label I think I've seen that particular style before, and chances are they just rebranded a Seventeam PSU.

I based my assumption on the overall appearance of the unit .. it reminds me of the many cheap shaw units I have opened in the past for post mortem investigations after they died in much the same way as OPs did.

OK, I had a few minutes to look at this, so here you go:

For both the 10V 2200 uF caps and the 16V 2200 uF cap, feel free to use 3300 uF if that's easier to find, especially if you can't find proper low ESR caps near you. In tha case, over-sizing the capacitance will give the new caps a higher ripple current rating, so they should last longer if they are GP caps. As for the PSU, it shouldn't care too much about the higher capacity (if anything, it helps it smooth out transients on the output.)

The 25V 1000 uF cap is for the -12V rail. A 470 uF cap would probably do the job too... but what the heck.

At best a 16v cap would suffice for the -12v rail. I've seen 16v caps for -12v in quite a lot of units, from as low as Deers to as high as Seasonic.

PcBytes wrote on 2024-04-20, 14:30:

At best a 16v cap would suffice for the -12v rail. I've seen 16v caps for -12v in quite a lot of units, from as low as Deers to as high as Seasonic.

Absolutely right.
For some reason while I was putting annotations on the above image, my brain froze for a second and I thought the -5V reg was a -12V reg... thus going with a 25V cap, as that's what most PSU manufacturers do that use a 7912 regulator for the -12V rail. But yes a 16v cap will do fine.

Trashbytes wrote on 2024-04-20, 14:10:

I based my assumption on the overall appearance of the unit .. it reminds me of the many cheap shaw units I have opened in the past for post mortem investigations after they died in much the same way as OPs did.

Well, you're not wrong to make that assumption, as most cheap gutless PSUs are clones of this old (half-bridge) AT design, but just with a 5VSB circuit added. The problem is not actually that they are clones of this design, but that they do with cheaper / smaller / inadequate parts while also greatly over-rating the stated values on their label. The result is a less-capable PSU that's asked to do even more, as there are (were) quite a few people unaware of these tactics.

Trashbytes wrote on 2024-04-20, 13:56:

Cheap as in good quality ones from a reputable fab except gigabyte, I usually run Seasonic or one of their known off brands they use for their cheaper models, Corsair also make good cheaper models.

Ah OK, I suppose we had different understanding of what cheap is. 😁
To me, cheap is "comes with the case" when the case is already a bottom-priced bargain 🤣

Corsair doesn't make their own PSUs, but rather uses various OEMs. Still, they've always used decent OEMs at the very least (the older CX units for example, are Channel Well Technology, IIRC.)
Gigabyte is the same... though they've used many different OEMs - sometimes not very good ones.

Trashbytes wrote on 2024-04-20, 13:56:

I always avoid the chinesium ones which claim 600 watts but weigh less than a sheet of paper, I still have nightmares of SHAW PSUs from back in the day that made such claims and then promptly took your entire system with them the moment you loaded them up.

I can relate. For me it was a very stripped down Solytech unit from their L&C line (basically bottom-of-the-barel units). With it, constant PC crashes under system load were the norm. However, I never realized that many of the crashes and "software" problems I had were actually hardware problems caused by the PSU... not until it randomly decided to short-out and smoke up on the floppy connector one day. Then I changed the PSU and all of the problems with that PC vanished for good. Interestingly enough, when the incident happened, the floppy connector was plugged into a floppy drive, but there was nothing wrong with the floppy drive itself. Regardless, that PSU was never plugged into a PC again.

Agree with momaka, this unit, if fitted with good quality capacitors, is very decent. Great even, considering that 230W is more than enough for your typical AT build.

More importantly, given how it’s built it can achieve the specified ratings which is what actually matters, so I’m not sure why some are so quick to dismiss units like this one.

Trashbytes wrote on 2024-04-20, 09:31:

oh my ...even if you did find the right caps I would seriously consider not plugging anything important into this.

This viewpoint really irritates me. Like the last Tony359 video [Let's fix this 𝗗𝗘𝗔𝗗 ATX power supply!] https://www.youtube.com/watch?v=n86eU5rsJds with that stupid (paraphrasing here): 'I was happily using this supply up to the moment it died, but now that Its fixed I wont touch it anymore!!1'. The F? :]
Everyone was using those supplies back in the day and computers werent blowing up nor houses burning down. It was good enough for ~150W up to socket5/7 of the era. Computers went from 150W to >=200W draw around 1998-99 but cheapest PSUs didnt keep up. People running beefy Athlon/Duron/P3 with first real GPUs, with multiple HDDs, CD burners, additional Fans etc all on noname "250W" PSU was when troubles started.

It's just one of the 1.943.254.243.434 TL494 based power supplies.
Put a blue led on it and will become future proof ...

Listen to Momaka e PcBytes ... they know their stuff.

rasz_pl wrote on 2024-04-20, 20:23:

Trashbytes wrote on 2024-04-20, 09:31:

oh my ...even if you did find the right caps I would seriously consider not plugging anything important into this.

This viewpoint really irritates me. Like the last Tony359 video [Let's fix this 𝗗𝗘𝗔𝗗 ATX power supply!] https://www.youtube.com/watch?v=n86eU5rsJds with that stupid (paraphrasing here): 'I was happily using this supply up to the moment it died, but now that Its fixed I wont touch it anymore!!1'. The F? :]
Everyone was using those supplies back in the day and computers werent blowing up nor houses burning down. It was good enough for ~150W up to socket5/7 of the era. Computers went from 150W to >=200W draw around 1998-99 but cheapest PSUs didnt keep up. People running beefy Athlon/Duron/P3 with first real GPUs, with multiple HDDs, CD burners, additional Fans etc all on noname "250W" PSU was when troubles started.

Notice I never said to not use it but rather keep it away from important "hard to replace" hardware, just because you replaced some caps doesn't means its "GOOD" to go, I've made that mistake in the past and been burned before, even after putting it through extra testing and it checking out as ok.

Also why use a known defective but repaired PSU when you have more reliable options, I understand his view point perfectly, though I would relegate the PSU he repaired to test bench duty till it had proven itself to be reliable and nothing further was going to die within. Old PSUs should be treated as suspect till proven otherwise even repaired ones, its cheaper to replace them that it is to replace rare hardware.

Trashbytes wrote on 2024-04-21, 01:01:

Also why use a known defective but repaired PSU when you have more reliable options

Do we have "more reliable options" when it comes to 5V 20A AT supplies? How would modern supply be more reliable when old one lasted >20 years before needing a service?
Is there something special about power supplies? From where Im standing its either repaired or its not. I wouldnt even consider this or the one from Tony359 video as broken broken, Electrolytic capacitors are consumables, and after all those years its more of a tune up job, like replacing spark plugs.
How about cars, would you advocate for replacing car after first defect and repair? 😀 Now you might say PSU is more critical, whats more critical than car brakes? Its like saying mmm that Golf Mk3/Passat B5 is nice and all, but it has been serviced before, dont drive it! 😉
Another example are motherboards from 2000-2010 period, most in need of new caps. It would be insane telling someone to never use such motherboard after cap job because its "unreliable" and could fry expensive rare CPU. 😀

Trashbytes wrote on 2024-04-21, 01:01:

Old PSUs should be treated as suspect till proven otherwise even repaired ones, its cheaper to replace them that it is to replace rare hardware.

I dont remember ever hearing about bad supply frying computer innards until we got beyond year 2000 into power hungry configs. Before that nobody even looked at PSU as something critical or important, it was just a stock part like floppy drive and all pretty much worked equally well. Supply in this thread looks like something straight from 286/386 clone.

AYE ! Agree with you rasz_pl ! Makes good sense.
My only concern on this PSU is a few missing caps on secondary side..in top picture..wondering why...
added: Did I miss their were already removed ?

rasz_pl wrote on 2024-04-21, 01:48:

Do we have "more reliable options" when it comes to 5V 20A AT supplies? How would modern supply be more reliable when old one la […]
Show full quote

Trashbytes wrote on 2024-04-21, 01:01:

Also why use a known defective but repaired PSU when you have more reliable options

Do we have "more reliable options" when it comes to 5V 20A AT supplies? How would modern supply be more reliable when old one lasted >20 years before needing a service?
Is there something special about power supplies? From where Im standing its either repaired or its not. I wouldnt even consider this or the one from Tony359 video as broken broken, Electrolytic capacitors are consumables, and after all those years its more of a tune up job, like replacing spark plugs.
How about cars, would you advocate for replacing car after first defect and repair? 😀 Now you might say PSU is more critical, whats more critical than car brakes? Its like saying mmm that Golf Mk3/Passat B5 is nice and all, but it has been serviced before, dont drive it! 😉
Another example are motherboards from 2000-2010 period, most in need of new caps. It would be insane telling someone to never use such motherboard after cap job because its "unreliable" and could fry expensive rare CPU. 😀

Trashbytes wrote on 2024-04-21, 01:01:

Old PSUs should be treated as suspect till proven otherwise even repaired ones, its cheaper to replace them that it is to replace rare hardware.

I dont remember ever hearing about bad supply frying computer innards until we got beyond year 2000 into power hungry configs. Before that nobody even looked at PSU as something critical or important, it was just a stock part like floppy drive and all pretty much worked equally well. Supply in this thread looks like something straight from 286/386 clone.

You do you my friend, I respectfully disagree with you and will leave it right there.

thank you @momaka for drawing out the caps. super helpful : ) I will order a few caps tonight.

as enthusiasts, we all know that there might be other options rather than repairing an old AT PSU, but the same could be said about nearly any other components in a 90's white-box pc. For me, cleaning and fixing these vintage components and then putting them all back exactly as the PC was decades ago is the most satisfying and nostalgic part of doing the whole vintage hobby thing 😀