Re: 5.25 card into IIGS

[Roger Johnstone <news2006@roger.geek.nz>]

In <1150795845.520962.52220@r2g2000cwb.googlegroups.com> mdj wrote:
> 
> Michael J. Mahon wrote:
> 
>> FWIW, I've never seen a decoupling capacitor on a card fail, unless
>> it was because its leads shorted or broke.  Undoubtedly it can happen,
>> but it is a very unusual event.
> 
> Seems like it's almost impossible, given that they're connected across
> the rails anyway. You'd need a fairly nasty current spike to pop one 
> of those.

It does happen though. I know, because my IIGS bears the scar to prove 
it. This is a repost of the story I told a few years ago:

A tiny surface mount chip capacitor on the _underside_ of the 
motherboard shorted and burnt up. 
It started with a tiny stream of smoke coming from the top of my IIgs, I 
immediately turned it off and opened it up. Close examination of the 
board 
and the cards revealed no obvious source of the smoke, so I left the 
cards 
out and turned it back on, with the top off of course. Immediately I 
could 
see, through one of the holes the motherboard has in front of each slot, 
a 
disturbingly bright orange glow reflecting off the shiny metal base pan! 
The 
capacitor was a bypass from the +5V rail to ground, it had shorted and 
the 
power supply was doing its best to clear the short by burning a hole 
through 
my motherboard! 

Fortunately no major damage was done, once I dug out the remains of the 
capacitor and some of the charred board everything worked fine. It's 
missing 
a bypass capacitor on slot 4 but since nothing's in that slot it doesn't 
cause a problem.

-- 
* Roger Johnstone, Invercargill, New Zealand -> http://roger.geek.nz
* PS/2 Mouse Adapter for vintage Apple II or Mac
* SCART RGB cable for Apple IIGS