Well, I couldn't find any concrete rules about necro-bumping timeframes (I admit I did not try very hard due to being too sick to really care) and this thread seems to be adequately relevant to my current repair project to bump, so...
I recently found my father's old Compac Portable III languishing upstairs outside of his office inside of its carrying bag. He says he got it right about when they came out, got the expansion unit, expanded the memory, got the 80287 math coprocessor, and got some networking or serial expansion card. Says he bought it for like $8k, which disturbs me because that's a lot even now and he basically just dumped it upstairs. I understand, as it's very obsolete, but at the same time...
Anyway, I plugged it in to see if it would boot up. I could hear it tick a relay repeatedly and it turned on its fan, so I assumed it was a power supply issue. I got the power supply out and tried it again out in the shop directly in front of my father's "smoking desk" so if I got electrocuted to death I wouldn't be in the abandoned upstairs offices. The power supply was able to run the fan and weakly trigger the relay only. I removed all of the electrolytic capacitors (except for the weird axial paper/polyester/whatever cap) from the board after labeling each by their accompanying silkscreen numbers, as I have a Fluke that can do capacitance measurements but I didn't think it can do so accurately with the components in place. Almost all of these aluminum caps tested at slightly over their labeled rated uF values, which my reading suggests does not indicate that they are actually healthy.
I honestly intended to just replace all of the electrolytic caps because I know that they have a somewhat limited lifespan and the electrolyte is not great for PCBs, but I have run into an unexpected problem: apparently these capacitors are not in physical sizes that places like Digikey and Mouser typically carry. The largest ones are so far where I'm getting stuck: there's a 6.3VDC 8200 uF that's 25mm diameter and 55 mm long, and another one that's something like 16V or 20V 1200 uF and 15mmx35mm.
I was wanting to get replacements from Nichicon, Rubycon, or TDK. TDK carries similar to the first one rated for a higher voltage and I think in a bigger can. My father (an electrical engineer) said that getting a cap rated for a higher voltage should be fine, but at the same time he doesn't want to talk about this at all and he doubts me when I say that electrolytic capacitors can fail by losing electrolyte over time due to not being hermetically sealed.
I will get all of the labeled ratings for the electrolytic capacitors, their dimensions, and also post the silkscreen labels for the wire connections (voltage and polarity mostly) as well as the wire colors for future reference or something (maybe tomorrow; I have written it all down and work is slow enough that I can also get out the digital calipers and measure lead spacing). Mostly, if anyone knows of where else I could try looking for these oddball sizes, I would really love constructive input. I would prefer that they be of high quality and not new-old-stock, since capacitors are pretty cheap as long as you're not buying hundreds or thousands of them.
