To Re-Cap or Not

[oldpcguy]

Recently I acquired a Packard Bell 80386 SX system which had a marginal power supply. After close inspection I discovered a number of leaking capacitors (you can read all about it here). I also own a Packard Bell 80486 DX system which is just slightly never than the 80386 system. It's power supply appears to be OK in that it delivers the expected voltages. However, given it is a Packard Bell system and the issues with the 80386 system I decided to inspect the 80486 power supply. I just removed the top cover and cannot see anything which looks to be an issue. I identified one ELNA branded capaitor (these were the ones which failed in the 80386 system) but it looks to be holding out OK.

I know there's a lot of different opinions on recapping something which doesn't appear to need recapping. But I thought I would throw it out there to get opinions. It's not especially difficult or expensive to recap these power supplies but I would prefer not to if there's no need to do so. What does the forum say?

 

[3lectr1c]

If it's ELNA, replace it. They are completely untrustable.
If it's another brand, inspect and then go from there.
Go ahead and post a photo of the PSU board as well, both sides.

 

[Chuck(G)]

Brand matters a lot. NCC and Panasonic caps are pretty good. Chinese ones, particularly the near-forgeries (e.g. Rulycon instead of Rubycon) are the most suspect.
Bottom line on it all is that ever since the ban on PCBs, electrolytics do have a fairly limited service life, regardless of brand. The folks who service my HVAC system routinely replace the start/run capacitors on the unit after 4 years (and can back up what they're doing by giving you the old one and letting you measure it yourself).

 

[Timo W.]

I know there's a lot of different opinions on recapping something which doesn't appear to need recapping.

True, but that rarely refers to PSUs. Since a malfunctioning PSU can kill the system attached to it, recapping (or replacing with a modern one) it is always a good idea.

 

[oldpcguy]

If it's ELNA, replace it. They are completely untrustable.
If it's another brand, inspect and then go from there.
Go ahead and post a photo of the PSU board as well, both sides.

If that's the recommendation then I will likely replace all of them. If I'm in there for one I might as well do them all.

 

[super-sama]

I'm a big proponent of leaving well enough alone if nothing looks suspect, but as with my reply in the other thread mere moments ago, yes, you should replace anything at all whatsoever that says Elna on it.
When I replaced all the capacitors in the custom power supply in the FedEx Powership 2 386SX machine of mine, of which the PSU was made by Teapo in '92, I replaced every single electrolytic, even the 50v 1uF caps that generally shouldn't matter, with ones from the Nichicon PS line. At the time a few years ago they were still active and plentiful, but Digikey/Mouser has them on clearance as Nichicon discontinued them. If you can still get all the correct values, I heavily recommend that particular family as the datasheet specifically says it's for general power supply use. Don't forget that after you do this, most switching supplies of that era are going to have a trim pot to adjust the voltage output and you should set it with a standalone load attached (i.e. hard drive you don't care about) so to have the voltage be mostly dead-on when you put it back into the motherboard.

I'm about to post a thread asking for info on the PSU used in my PS/2 so to get a cap list, but it's a bit on the harder side to remove and open due to IBM using security torx, something I don't readily have available on hand so far as I can tell. Used to, but that's what happens when you move house!

 

[Unknown_K]

If you know a brand is fake and you find it in your system you should replace the part. In general, on power supplies, I just replace the part that goes bad. On motherboards that don't have leaky SMD electrolytics I replace whole sections of capacitors around the heatsink that get over heated. It's easy enough to pop off a suspected cap and connect it to an ESR meter or a parts tester and see if it is in spec or not.

Some devices were designed badly and put too much stress on particular parts that will eventually fail. You don't go around replacing everything for no reason.

 

[oldpcguy]

I'm a big proponent of leaving well enough alone if nothing looks suspect, but as with my reply in the other thread mere moments ago, yes, you should replace anything at all whatsoever that says Elna on it.
When I replaced all the capacitors in the custom power supply in the FedEx Powership 2 386SX machine of mine, of which the PSU was made by Teapo in '92, I replaced every single electrolytic, even the 50v 1uF caps that generally shouldn't matter, with ones from the Nichicon PS line. At the time a few years ago they were still active and plentiful, but Digikey/Mouser has them on clearance as Nichicon discontinued them. If you can still get all the correct values, I heavily recommend that particular family as the datasheet specifically says it's for general power supply use. Don't forget that after you do this, most switching supplies of that era are going to have a trim pot to adjust the voltage output and you should set it with a standalone load attached (i.e. hard drive you don't care about) so to have the voltage be mostly dead-on when you put it back into the motherboard.

I did exactly that with the 80386 power supply. Didn't need to adjust the pot (thankfully as it was glued in place) as the voltages were now in spec.

I'm about to post a thread asking for info on the PSU used in my PS/2 so to get a cap list, but it's a bit on the harder side to remove and open due to IBM using security torx, something I don't readily have available on hand so far as I can tell. Used to, but that's what happens when you move house!

They're no longer "security" torx bits as they're easy to buy just about anywhere. I picked up a set at Home Depot years ago. I did recap a PS/2 Model 70 supply, easy and painless.

 

[oldpcguy]

If you know a brand is fake and you find it in your system you should replace the part. In general, on power supplies, I just replace the part that goes bad. On motherboards that don't have leaky SMD electrolytics I replace whole sections of capacitors around the heatsink that get over heated. It's easy enough to pop off a suspected cap and connect it to an ESR meter or a parts tester and see if it is in spec or not.

Some devices were designed badly and put too much stress on particular parts that will eventually fail. You don't go around replacing everything for no reason.

My thought is if I've already got it apart to replace one capacitor I may as well do them all. It's just a little more time and money.

 

[oldpcguy]

I think I've decided not to recap this power supply, at least not at this time. After disassembling I was unable to find any traces of leakage, even on the Elna capacitor (maybe I should just replace this one, it wouldn't be difficult?). Here are top and bottom side pics along with some additional ones. Please let me know if you see something I am not (brown stuff on the bottom is just flux from the manufacturing process).






Elna capacitor:



Group of capacitors which I cannot easily inspect. Bottom side picture is where those caps are soldered to the PCB:

 

[3lectr1c]

All of those capacitors in that supply of that brown color are ELNA, you can tell by the shape of the safety vents on top. If you ever see that style of safety vents in something, it’s ELNA. No visible signs of leakage is good - that means your recap job will go easier as there will be no mess to clean up.
I completely understand leaving something working alone, but you just can’t trust any ELNA caps nowadays. If you wait, that supply WILL die, and then you’ll have a nasty mess to clean up to boot.

 

[oldpcguy]

All of those capacitors in that supply of that brown color are ELNA, you can tell by the shape of the safety vents on top. If you ever see that style of safety vents in something, it’s ELNA. No visible signs of leakage is good - that means your recap job will go easier as there will be no mess to clean up.
I completely understand leaving something working alone, but you just can’t trust any ELNA caps nowadays. If you wait, that supply WILL die, and then you’ll have a nasty mess to clean up to boot.

Thanks for this information. With it I think I'll go ahead and recap it. Now to find the time.