"Sander deWaal" wrote in message
...
"Robert Morein" said:


What about the old CDR tubular foil caps I used? How good are they?


Dunno, I'm not familiar with them.


Please do replace the remaining old capacitors, apparently they are
prone to shorting.


Apparently. The next time one shorts, I'll do the rest.


Please do it soon.
Scott already told what can happen when a cap shorts.
A supply rail going down via a foil cap may damage your amp, and take
several other components with it.

The reason I'm not doing it is:
1. When I took the amp apart, I discovered a similar failure, but in an area
that was not clearly a rail bypass, that had gone unnoticed, for a total of
two.
2. This means that I would have to do every foil cap on the board. There are
quite afew. The amp works great.

One thing that might have provoked it is the use of a Parasound SCAMP
(signal controlled amplifier power). It senses the presence of audio, and
turns the power to the amp on and off. This one was glitching quite a bit,
rapidly turning the amp on/off at random intervals, due to noise from
computer switching supplies. I have since moved the audio to a separate
dedicated line. I speculate that the rapid cycling might have caused
inductive spikes from the collapse of the power transformer field. Or, the
life cycle on/off count may have been considerably exceeded.

This amp succeeded in incinerating two caps, and afew neighbors, with no
collateral damage where it hurts, ie., a transistor. Rather than rework the
board, I'll take my chances.