Virgin? Bizarre choice of words. Recapping won't hurt especially if you use high quality Japanese caps.

altair 8800 cira like 1975? caps that old probably vapourised to some degree, I'd recap any directly on the power rails or any big filter caps, any rifa caps and leave the rest alone

dominusprog wrote on 2024-09-24, 12:21:

Virgin? Bizarre choice of words.

Meh, I just woke up.

dominusprog wrote on 2024-09-24, 12:21:

Recapping won't hurt especially if you use high quality Japanese caps.

There is a small risk since the wires on this machine were notoriously prone to breakage and are almost 50 years old now. However I was more concerned with collector/historical value. If I do recap, I was planning on using KEMET's PHA223JLP4320ME4, sourced from digikey. Based on specs, I these caps should last another 40 years.

BloodyCactus wrote on 2024-09-24, 13:41:

altair 8800 cira like 1975? caps that old probably vapourised to some degree, I'd recap any directly on the power rails or any big filter caps, any rifa caps and leave the rest alone

Yep 😄. The OG personal computer. Rev 0 too! Normally I'd just recap anything over 20 years old without a second thought, but this bad boy is rare and actually has historical significance. You don't want to know how much it cost.

I have found capacitors from the 70s and earlier to be fairly reliable. It wasn't until the 90s that the quality of electrolytic capacitors started to drop. If anything it was the exotic low leakage capacitors that were more likely to fail.

Most likely if there are any capacitors that exhibit electrical leakage can be safely reformed.

akimmet wrote on 2024-09-24, 23:01:

Most likely if there are any capacitors that exhibit electrical leakage can be safely reformed.

Reforming capacitors had never occurred to me. I'll look into that. Thanks. I'll break out my LCR meter and start testing the parts.

I got burned quite a bit by the capacitor plague back in the early 2000s, so since then I've always had the mindset of when in doubt, replace. That experience also gave me the habit of WAY over specing parts for their rated lifetime. If I need to to last for 10 years, choose parts that will last for 40 years at my expected load and temp.

Overkill wrote on 2024-09-24, 13:54:

dominusprog wrote on 2024-09-24, 12:21:

Virgin? Bizarre choice of words.

Meh, I just woke up.

Pristine might have been the word you were looking for.

Though something that hadn't been tampered with by a big, bad soldering iron might still be considered a virgin, too.

akimmet wrote on 2024-09-24, 23:01:

I have found capacitors from the 70s and earlier to be fairly reliable.

Caps don't last forever, but I was going to say something like this, as well.

I do have an Yaesu FT-101 HF radio and a Robot Model 400 SSTV converter from the 1970s that work without maintenance.
And a couple of RTTY decoders from about same time, too.