9 Sep
2006
9 Sep
'06
11:07 p.m.
----- Original Message -----
From: "Ethan Dicks" <ethan.dicks at gmail.com>
To: "General Discussion: On-Topic and Off-Topic Posts"
<cctalk at classiccmp.org>
Sent: Sunday, September 10, 2006 12:48 AM
Subject: Re: Broken Mac Accelerator
capacitor.
On 9/10/06, Tony Duell <ard at
p850ug1.demon.co.uk> wrote:
> >
> > So what I want to know is how the thing functioned at all without the
=
> > cap (burnt carbon acted as a capacitor in
some way)? and what caused
it =
>
> That cap[acitor was probably a tantalum electrolytic (this being the
type
normally known
for exploding in this manner) and was probably a supply
decoupuling capacitor.
> > to stop working.
>
> Now that I don't know, but it may have nothing to do with that
Perhaps there was some PCB damage under the exploded cap? We had
a tantalum cap (16uF?) blow on a COMBOARD that was installed in a
crowded BA-11... it looked like someone shot the board with a .22. The
boards on either side were damaged as well, but not perforated.
Since the OP described blackening, perhaps it might be worth a few
minutes to gently remove the residue (95% Isopropyl (1,2-propanol?)) and
a soft toothbrush should get most of the crud off - then check the traces
and see if there's any visible damage.
Even if that's not where the problem is, a gentle cleaning should hurt
anything.
-ethan
I cleaned the burnt material off and all I see is the fiberglass weave
texture (the pads the cap were on are long gone). The cap was in the general
area of the processor (back side of the card) and it looks like atleast one
leg of the oscillator that controlled the circuit went to it. While there
are a bunch of tracks around the area I don't think any were directly
underneath the area that is damaged or it never would have worked at all.
The before shot is here:
http://home.neo.rr.com/unknownk/images/blown_cap.bmp
