On 06/03/2017 21:56, Gareth Magennis wrote:
This is a bit weird.

I have an audio power amplifier that uses what looks like strips of pink
silicone sheet between the output transistors and the heatsink.
But these strips have degenerated and are kind of squidgy, a bit like
when Speaker surrounds fall apart.
Not come across this before.

They have got so bad that an arc occurred through one strip, beneath one
of the transistors, which has burnt a small hole in the heatsink,
blowing the amp and the SMPS, which I repaired.


So what kind of material could this pad be made of? Surely silicone
wouldn't do this?



This is the amp, you wouldn't expect this kind of problem on something
like this.

http://www.dbaudio.com/en/systems/de...amplifier.html



Cheers,


Gareth.

Stay with mica slivers, been around for geological time, no plasticer to
leach out. The only time I've come across failure of a mica insulator
was when some swarf got under it at manufacture, that would do for all
other insulators as well.
Trouble with mica is it is dirt cheap and not patentable.