At 04:00 PM 7/19/99 -0500, you wrote:
>OK, let's walk through this. First you had "one visibly fried
>resistor R610". I wouldn't think that could even happen, but
>I suppose if R620 opened and the yoke kicked back through
>it that R610 could get damaged, along with Q603.
>
>You then replaced "several dead components: R620, R610,
>Q603, Q605". Well, there is Q603 and R620, and I can
>believe the other two.
>
>Once fixed "R618 and R613 were killed with extreme prejudice".
>Hmmm, acts like the heatsink (or any lead) of Q606 is shorted to
>ground? Or Q607. Or a solder short on ANY of the replaced
>parts.
I tested both Q606 and Q607 out of circuit, but didn't look
for a short. As far as a solder short might go, <is it
getting hot in here or is it just me?> while trying to see
why the board caught fire on me, I happened to flip the
board over and see a little sliver of solder at one corner
of the solder-side of the board (I don't think it was there
when I fried the resistors, but anything is possible).
When I barely touched the sliver, it fell on the ground,
I may even have just breathed on it.
>Another possibility is that either D606 or D607 opened.
>This would crank all the currents up and cause just what
>you have.
I will check all of the diodes tonight including D606 and
D607 and I will check the 2 transistors w/ the heat sinks
for grounding issues. I'll let you know how it goes
tomorrow. Thanks a *lot* for looking at this for me!
Jon
Received on Mon Jul 19 16:59:25 1999
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