Do you need all transistors need Mica Insulator?

[Jam]

I got some Sanken 2SC3264 transistor and a 2sc3834 to install and when I removed them I didn't see any mica? Do I need them? Thanks for any input

[Enzo]

Hi Jam

That is kinda like asking if I need to wear a coat when I go outside. it all depends, is it winter or summer? AM I in FLorida or Canada?


What are they going into? It would be very unusual to not need an insulator, but there are amps that don't.


Look very closely, what looks like just a smudge of white heat grease can still hide a mica washer. And make sure they are not stuck to the old parts.

The mica insulates the metal backside of the transistor from the metal heatsink, which is usually grounded. There are some transistors with completely insulated backsides, and those do not need insulators.

[The Dude]

There are also cases where the heatsink is not at ground potential. Simply soldered into the board "floating" with no electrical connection other than the transistor tab- another case where insulators are not used.

[Jam]

Im very dumb I scraped the grease and found them. The only one not to have one was the thermal switch do they need one? Thanks

[The Dude]

If it didn't have one, it probably doesn't need one. If your in doubt, check for continuity between whatever part of the device might touch the heatsink and the legs or electrical connections to the device. If there's no internal connection in the device, you don't need an insulator.