How long caps last 27 years?

[vintageibm]

Hello, I have a power supply that is 27 years old from 1984. I was wondering if it would be worth while to go in and re cap the entire power supply to protect the computer system and power supply, I see notes online that when the caps go it takes a lot of other parts with them. The system and power supply work fine. Would I be asking for trouble or would it be good maintenance? Thanks for any input. It's an 83 watt SMPS in an old IBM 5150pc.

[goodpsusearch]

Re: How long caps last 27 years?

It depends on many things, hours of daily use, temperature of the caps, how much ripple they get etc.

[vintageibm]

Re: How long caps last 27 years?

The system only see's 2 hours of use every two months, just to keep the caps "healthy" The caps in the PS are rated for 105C don't know there temp but they must stay cool big PSU case and a fan right on top of them. Don't know the ripple or how to test it?

It depends on many things, hours of daily use, temperature of the caps, how much ripple they get etc.

[Trinite]

Re: How long caps last 27 years?

I have an old TV stereo decoder board here that looks like it was manufactured week 36, 1973 and all the electrolytics are still good. All the caps are either Nichicon or Chemicon.

[TheLaw]

Re: How long caps last 27 years?

Depends on the brand, temperatures they were exposed to, voltage that was being run through it, and the running time.

But, yes it is possible. I have some really old electronics that still work and they are REALLY old.

But it is for a computer which is going to be more sensitive than say a DC motor. I'd say measure all the capacitances with a multimeter and check if any of them are WAY off from their printed spec. Remember: Electrolytics have a huge tolerance margin, so the capacitance would have to be maybe 40-50% off the printed spec to make it worth while.

If alot of them are off, you might want to consider doing the whole board. If only a few, maybe just replace those 3-4. If there is a PFC cap, you should definitley replace that. If not, the main big filter cap should probably be replaced regardless.

Correct me if I am wrong, but just what I have observed.

[Krankshaft]

Re: How long caps last 27 years?

Active PFC in a computer PSU from 1984 not a chance.

They used line voltage power switches on those monster PSUs.

As for old cap life I have aluminum can lytics in my early 1980 Tektronix scope still in perfect condition going on 31 years. But I could see when I bought it the scope had only seen light use.

I also have a 1948 Kodak 16mm projector with aluminum can sealed lytics still in working condition when I bought it. I recapped it preventatively. I was digging in there to replace selenium rectifiers anyway.

Life all depends on hours of use, temperature, ripple, and on old equipment seal design. If the bottom seal remains intact and the electrolyte doesn't evaporate out even a cap not in use can have an long life.

On modern equipment you can only control the first 2 factors to maximize cap life.

[vintageibm]

Re: How long caps last 27 years?

All caps appear to be Marcon and Nichicon. The two large caps are 220Uf 200v.

I have no ideal on there past use, this PSU (in the photo) has seen tons of use, the one I am asking about is a low use system. Don't think it saw much use at all.

[vintageibm]

Re: How long caps last 27 years?

I went ahead and toke this one all the way apart, I toke my DVM, set on 2000K. The two big caps started at 0 and the numbers started going up pretty quick... On the group of 5 caps over by the heat sinks all of those started at and stayed at 0 got to 5 at the most. My knowledge is very very limited in the subject. But from what I have seen online the two big caps are good because that means they are charging and one or all 5 caps are bad because it's at 0 like a wire? This was done on the board nothing removed. The one cap at the bottom edge of the board next the little transformer did the same thing started charging, so I assume that's a good one?

[Th3_uN1Qu3]

Re: How long caps last 27 years?

You need an ESR meter to test the capacitors. If the caps were shorted the system would not work at all, so that isn't the case here.