Hi Malcolm,
Wow! Cool fireworks!
I've only encountered 3 shorted tantalum's (on vintage computers) to date. 1 on an 8" drive, 1 on the Mother board of the IBM 5150 and 1 on the keyboard for that 5150. I've seen others in my years of repairing (contemporary) stuff, but it's not all that common. The age difference between the oldest I've seen short and the newest must be 15+ years.
I'm no expert in this field, but my experience tells me it's not age related. More like a manufacturing defect, randomly occurring, however, I will guess age and heat will likely contribute to it's failure. I suspect heat over time to be the major factor in triggering a randomly defective capacitor.
I don't believe the other 17 capacitors are likely to blow up just because this one did.
But then there's Murphy's law, so I will restate my last sentence to "...other 16 capacitors..."
Cheers, Josh
From:
mal...@avitech.com.auTo:
n8vem...@googlegroups.comSubject: [N8VEM-S100:5163] Tantalum capacitor replacement?
Date: Mon, 8 Sep 2014 12:16:08 +1000
A couple of questions about tantalum capacitors in S-100 systems…
I have a 12-slot CCS chassis that I’m working on.
When I powered it up a tantalum capacitor on the backplane disintegrated quite spectacularly. It was across the -16V rail. It took out the -16V PCB trace, triggered the circuit breaker on the chassis back panel, and blew a 2.5A fuse on the 240V side of the stepdown transformer that I’m using. So it must have been a decent internal short! The two halves of the capacitor were later found on the opposite side of the room.
Would it be wise to replace the other 17 tantalum capacitors with new ones, to minimise the risk of similar failures – or are tantalum failures not largely age related?
Or perhaps I should just remove them? I’ve seen other backplanes with no capacitors – so perhaps these aren’t really all that important?
(The tantalums are across the 3 power rails – so groups of 3 capacitors at every second S-100 connector).
Malcolm.
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