Vintage Apricot another success but exploding caps

[roadrash]

Just aquired vintage Apricot PC (1982). It must have been in a damp muddy place cos it had mud inside and hundreds of spider skeletons and webs. I stripped cleaned and then laid it out on the table for its first test. It has a very similar Astec PSU like another Osborne I am also working on. I turned it on for like 2 seconds at a time just to check it wasn't going to go bang and no it didn't and was quiet with fan spinning. So hooked it up to the motherboard and disk drives and tried again turning it on for gradually longer periods until it eventually completely booted into like and it was all working OK. Then I kept trying and watching the filter caps and right enough in the end they blew first the larger 0.1uf then the 0.01uf which completely exploded. Replaced them all now and its working great. Surprising considering how old it is and the filthy muddy environment it was sitting in for who knows how many years. Shows the old stuff was definitely built to last. Here are a few pics

[PeteS in CA]

Re: Vintage Apricot another success but exploding caps

IIRC, Apricot was a UK-based company that produced Apple II+ or IIe clones and were driven out of business by patent violation lawsuits.

Interesting that the markings on the switch transistor weren't wire-brushed off.

I know that Rifa PME271 safety agency approved capacitors are not held in high regard by some here on BadCaps (I'm not one of them, FWIW), but that microcomputer has seen a bit od abuse. I'm guessing those X-caps took quite a few surges and spikes, and finally were so damaged that they self-immolated.

Back in the late 70s and early 80s, Rifa was the first producer of safety agency approved capacitors to catch on in the US and Asia, and for a time were pretty much ubiquitous.

Edit: I should add that I think at least some of those output capacitors might be higher quality 85C general purpose parts. I believe those light blue capacitors are Nichicon 85C parts, and UCC/NCC's SM (?) series 85C general purpose caps were also sometimes used as output capacitors (including by Astec). I'd keep an eye on those.

[roadrash]

Re: Vintage Apricot another success but exploding caps

I should add that I think at least some of those output capacitors might be higher quality 85C general purpose parts. I believe those light blue capacitors are Nichicon 85C parts, and UCC/NCC's SM (?) series 85C general purpose caps were also sometimes used as output capacitors (including by Astec). I'd keep an eye on those.

Thanks for that info on those blue Caps. Will they pop like a tantallum type or how will I know if they are failing?
I was ready and wary of those Rifa filter caps when I powered it up but just wanted to see if this thing was going to work before making a shopping list of parts i will replace. I would have changed them first and foremost knowing there poor reliability. I'm just pleased its all working and now I can get on with the full restoration.

[Agent24]

Re: Vintage Apricot another success but exploding caps

I turned it on for like 2 seconds at a time just to check it wasn't going to go bang

That's actually a good way to make an SMPS go bang! SMPS do not like getting turned on and off quickly.

Besides, if it's got a primary side fault, 2 seconds is more than enough time for it to blow.

A 'dim bulb tester' or other current limiting device would be a much better idea.

[PeteS in CA]

Re: Vintage Apricot another success but exploding caps

Thanks for that info on those blue Caps. Will they pop like a tantallum type or how will I know if they are failing?

I was ready and wary of those Rifa filter caps when I powered it up but just wanted to see if this thing was going to work before making a shopping list of parts i will replace. I would have changed them first and foremost knowing there poor reliability. I'm just pleased its all working and now I can get on with the full restoration.

Most likely they would be dried out and the ripple way out of spec. I'd go so far as to suggest replacing them out of hand, using Rubycon YXB or Nichicon PS series parts. Those are very mature series and barely qualify as low impedance. But they're 105C parts and probably not too much better than the original parts (I don't think they'd cause loop stability problems.

The 5V O/P caps are ~35 years old too, so replacing them might be reasonable. I'd try to find datasheets for the series used, just to be sure, but the YXB and PS series are probably decent matches.

Rifa makes good stuff. A Roederstein, Wima, or Siemens part of that era probably would not have fared any better.

[Wester547]

Re: Vintage Apricot another success but exploding caps

Most likely they would be dried out and the ripple way out of spec. I'd go so far as to suggest replacing them out of hand, using Rubycon YXB or Nichicon PS series parts. Those are very mature series and barely qualify as low impedance. But they're 105C parts and probably not too much better than the original parts (I don't think they'd cause loop stability problems.

The 5V O/P caps are ~35 years old too, so replacing them might be reasonable. I'd try to find datasheets for the series used, just to be sure, but the YXB and PS series are probably decent matches.

The attached discontinuation notice mentions that YXB was discontinued nearly 17 years ago. Unless they did what Nichicon did with the PA series - discontinue the ancient series and launch a new, RoHS series decades later? I'd say Rubycon YXF, Nichicon PM, PJ, and PS are good choices, as may be Chemi-con LXV or LXY.

[PeteS in CA]

Re: Vintage Apricot another success but exploding caps

The attached discontinuation notice mentions that YXB was discontinued nearly 17 years ago. Unless they did what Nichicon did with the PA series - discontinue the ancient series and launch a new, RoHS series decades later? I'd say Rubycon YXF, Nichicon PM, PJ, and PS are good choices, as may be Chemi-con LXV or LXY.

Mea goofa! I meant the YXF series. Re the other series: I'd do PS or PM first; PJ and LXV are similar and next; then LXY, which is close to the current (non-aqueous) LXZ series.

What Nichicon did with the PA series is odd, but I think they just reached PZ and returned to the start of the alphabet. Just like the better known Ford Model A was Ford's second Model A (the first being much older).

BTW, the new PA series has impedances almost as low as the HE series.