On Monday, March 6, 2017 at 4:56:49 PM UTC-5, 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.

I haven't had one fail in use, but have had a bunch fail when the device is replaced for other reasons. Often they'll be so acclimated to their heatsink they're virtually bonded, and they tear when removal is attempted. In a pinch I've used mica washers and a tiny schmear of 3M compound. I also have tons of older plasma SMPS that used them, so I have donors. They're also available from most supply houses.