Old PC PSU making noise etc

[roadrash]

A vintage 1980's PC power supply has started making a hissing and whining/squealing noise and the PC is now giving random errors like memory and video etc. Ive tried the PSU with just the Motherboard plugged in and its quiet but soon as I increase the load adding controller interface cards and drives etc, the noise starts. I think there is something about to fail but cannot see anything like a bulging cap or anything. Does anyone know whats the most likely suspect component? Here is a link to a video i took.

[stj]

re-cap it

[roadrash]

Thanks STJ, i was going to do that but just wondered if there was anything else that could make that noise. Will i need to replace those 2 large cans as well.

[stj]

coil noise is often caused by the psu running at the wrong frequency or being overloaded.
small caps can effect the pwm circuit.

*and warn people that your video is 150M in size

[roadrash]

Thanks Stj, thats what i thought i had heard before that a whining noise was a coil or something. Thats interesting i signifies there is somethings not right. Ok will get all those caps changed. Thanks you thats a great help .

[PeteS in CA]

When you do the re-cap, be aware that using the latest and greatest low impedance electrolytics could cause stability problems. I would suggest Nichicon PJ or PS series if either is available, and as second choices, PM or PW series.

[roadrash]

I took all the electrolytic caps out of my PSU today and what a hard job it wad getting the 2 big 200v ones out as they were glued in good and proper. Well just out of interest i tried each one on my component tester and this are the results.. not sure what is a bad ESR etc so do any look like they are bad?

PSU Caps tested
==============

16v 3300 x2 off (C27+29)
(1) Measures: 307.4 uf
Vloss: 1.8
ESR: 0.06 ohm
(2) Measures: 3020uf
Vloss:1.6
ESR: 0.08 ohm

16v 47uf (C35)
Measures: 46.87
Voss: 2.1
ESR: 1.0ohm

200wv 680uf x2off
(1) measures: 602.5uf
Vloss: 0.6
ESR: 0.8
(2) Measures: 606.2UF
Vloss: 0.9
ESR: 0.8

16v 330uf x3 off (C21 + C24 + 30)
(1) Measures 281.9uf
Vloss: 2.1
ESR: 0.20ohm
(2) Measures: 792.6uf
Vloss: 1.9
ESR: 0.23ohms
(3) measured 282.6uf
Vloss: 1.9
ESR: 0.22ohm

16v 1000uf (C31)
Measures: 850.8uf
Vloss:1.9
ESR: .12 ohms

[stj]

the 330uf cap that read as 782 is leaky as fuck.
i'm surprised the tester didnt catch that.

[roadrash]

the 330uf cap that read as 782 is leaky as fuck.
i'm surprised the tester didnt catch that.

Thanks, unfortunately that was a typo it should have read 292uf. I only copied and pasted so dont know how that happened.
is there any others not showing particularly good so i can know there was a problem with a cap or two and should i still replace them all.

[roadrash]

When you do the re-cap, be aware that using the latest and greatest low impedance electrolytics could cause stability problems. I would suggest Nichicon PJ or PS series if either is available, and as second choices, PM or PW series.

having difficulty finding capacitors of the series like you recommenced,. The two Big 200v 680uf nichicon caps in this PSU are marked PS(M) which google states "PS(M) is a series of polarized aluminum electrolytic capacitors with a P for polarized, S for a series designation, and (M) for a tolerance rating of ±20%., These are general-purpose capacitors designed for a wide range of applications" is this correct because I too think they should be long life type. if I can find some. Id there a special marking or prefix number that identifies this series of caps.

[roadrash]

I can see now Nichicon Caps beginning UP? denotes P series thanks and EL? is snap in type. Still hard to find a Nichicon Cap like you recommend. Does it matter that I use a snap in mounting type or how critical is the size? If for say I can find a P series cap but its a leaded type and a bit smaller than the original size would this matter? Also what is an acceptable impedance range?

[momaka]

You can leave the big 200V caps alone, as in, not buy new ones. The old ones measure fine and won't give you issues. On non-APFC PSUs, those large HV caps almost never fail. So save yourself the money and hassle with trying to replace those. From your list of the caps that you posted above, the one 3300 uF (C27) cap that measures 307.4 uF is definitely bad... unless that was a typo as well?? Is that all of the caps in the PSU? I suspect there should be lots more small ones... and usually these are the ones to fail "silently" (ironic, given the PSU's symptoms, isn't it ) without bulging or leaking. So it might be worthwhile to check all of the small caps, especially ones near heatsinks or other large/hot power components. While at it, check the solder joints in the PSU too. Also, how are the motherboard caps? Any suspicious brands to beware of on there? Just asking, because I don't like to jump to the conclusion that the PSU is causing the issues here... at least not without confirming that the issues do go away with another PSU.

[stj]

is this psu AT or XT?

[roadrash]

You can leave the big 200V caps alone, as in, not buy new ones. The old ones measure fine and won't give you issues. On non-APFC PSUs, those large HV caps almost never fail. So save yourself the money and hassle with trying to replace those. From your list of the caps that you posted above, the one 3300 uF (C27) cap that measures 307.4 uF is definitely bad... unless that was a typo as well?? Is that all of the caps in the PSU? I suspect there should be lots more small ones... and usually these are the ones to fail "silently" (ironic, given the PSU's symptoms, isn't it ) without bulging or leaking. So it might be worthwhile to check all of the small caps, especially ones near heatsinks or other large/hot power components. While at it, check the solder joints in the PSU too. Also, how are the motherboard caps? Any suspicious brands to beware of on there? Just asking, because I don't like to jump to the conclusion that the PSU is causing the issues here... at least not without confirming that the issues do go away with another PSU.

Thank you very much for taking the time to help with that info. Ok I will put the 3 big caps back in. There are no other smaller caps except tantalum type ones. I read on my history notes when i first got this and turned it on it blew up a tantalum cap which after it was replaced the computer worked. These new faults that have started are frustrating because there are no visible signs of any bad caps. The main computer PCB just has little bead type caps. Here is a photo of the computers PCB. I have has this working ok when i first started using it and then it started giving memory and graphics errors and at the same time I heard the PSU making the whining noise so just put it all down to a PSU problem making the computer unstable.

[roadrash]

is this psu AT or XT?

Its a AT PSU

[stj]

i just use panasonic FR in those

[Agent24]

If you already had one blown tantalum, you may have others not far behind. A partially shorted one could cause overloading. Might pay to replace the lot when they're that old.