On Mon, 6 Mar 2017 21:56:45 -0000, "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.


Back in the 70s they used Mica insulators, and coated them with silicone
grease to transfer heat. Unless the installer cracked them during
installation, they probably last forever.

I suppose they now came up with some cheap crap substance to save a
buck. If I ran across this, I'd change all of them with the old mica
types before more stuff burns up.