Dan K wrote:
"Arfa Daily" wrote in message
news
"Mark D. Zacharias" wrote in message
. com...
Arfa Daily wrote:
"Mark D. Zacharias" wrote in message
et...
I powered the amp back on and it worked. The only difference
being I was running without a heat sink now.

Perhaps the output transistors weren't insulated from the heat sink?

Mark Z.

That was my first thought also, Mark, but if you go up 4 posts, you
will see that he makes a point of saying that he checked that the
devices were isolated from the heatsink. It's a mystery ... |:-{

Arfa
Could have a damaged insulator...

mz

Could be. Might just be the way we are interpreting " checked ". When I
check that devices are isolated from a heatsink, I prove it with a meter
reading. Perhaps he was just visually inspecting ...

Arfa

Nope, meter reading. Isolated. It wouldn't have worked for a while if they
wasn't isolated, Vee would be shorted to Vcc. Could always be a crack in
the insulator I suppose that only shorts at certain times...They look ok
though

Sometimes you'll get a little 'burr' of sharp metal around the holes in
the heatsink. It reads fine when cold, but when it heats up the burr
expands enough to short through the insulator.

Clean off the sink, and feel for any sharp points.

jak

Dan