Computing > Vintage Computing

Repair/Restoration of Vintage Computer devices with Tantalum Capacitors

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CkRtech:
I pitch this thread as a philosophy question regarding old computer components. I have in recent years started restoring and building old computers as a hobby - mostly working with what I have had in my possession for a couple of decades. I am looking at a new restoration project within the next few months with components that stretch into a period (<= 1994) of using of candy-dipped tantalum caps on expansion cards and motherboards. This is where my vintage computing hobby gazes at a potential pit stop with my electronics hobby.

These caps have potentially not seen power for 25+ years. I have seen one user experience an IBM 5150 have one tantalum on its motherboard "go popcorn" - leaving a noticeable mark around the area where it used to reside.

I would prefer to avoid situations like those, but my question to you guys is - how proactive should one really be? In the case of acquiring an IBM 5150 that hasn't been powered up in goodness knows how many years, I am convinced that those caps should just be replaced proactively. But what about something newer (1993)?

I have attached an example of a early-mid nineties video card containing some of the caps. It represents a component of a computer I should reacquire from a relative soon. In addition, I believe the motherboard also might have a few. We're looking at 486 era, here. I last had it powered up in 2010 - and nothing happened at that point. Still - it certainly won't be the last bit of hardware I acquire like this, and for sure won't be the oldest.

helius:
Tantalum capacitors are "self healing", meaning that they regrow the barrier layer if there is a crack in it. The problem is that this healing process releases oxygen and heat, which in large amounts can allow combustion. It only happens if there are cracks in the dielectric, and those are not normally present simply because the assembly is old: age does not contribute to tantalum failures.
The short of it is that if you wouldn't replace all the tantalums on a brand new card, there is no reason to do so on an old one.

woodchips:
Good grief! Age doesn't contribute to tatalum failures! So what does? Come 20+ years and popping tants is almost a musical score.

Must say my direct experience does not reflect that statement, but what else could it be?

helius:
It is entirely possible that the operating voltage drifts high on boards where parts have aged. For example, if there is a trimmer pot on the power supply that controls the output level, and it has gotten dry and dusty. This can kill tantalums when the electric field strength is high enough to begin the "self healing" process in locations it has not yet happened.

eugenenine:
looks like VLB.

I have an Amiga 2000 on my bench I'm trying to revive.

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