Checking that transistors are isolated from ground

[pjpoes]

When you mount a transistor to a heatsink and use an isolater, like a Silpad. How can you be sure its isolating correctly. my amplifier is drawing too much current on the positive rail, and I have this suspicion that is the problem. However I can't figure out how to trace it out. Thanks.

[teemuk]

The bare metal surface that dissipates the heat is in the same potential as collector so simply measure resistance from collector to ground.

[pjpoes]

What part of the transistor is the collector, would that be the Gate? If you could give it to me in terms of Gate, Source, and Drain, that would help.

[teemuk]

Ok, I didn't realize you were talking about field effect transistors..

Gate corresponds to bipolar transistor's base
Drain corresponds to collector
Source corresponds to emitter

[AndrewT]

Hi,
as far as I know the middle pin of SIL transistors is connected to the mounting flange.
This applies to BJTs, Vertical FETs and Lateral FETs.

Regulators are different.

Look up your data sheet, the information is detailed there.

[pjpoes]

Thanks Andrew, I looked up the datasheet and didn't see where it said that. None the less, you are right, and I figured it out eventually. I found the problem, some left over heat sink compound that was mis-placed. It's currently playing music, so all is well. Again, thanks to everyone though.

[AndrewT]

I found the problem, some left over heat sink compound

Hi,
that was not your problem.
What else did you correct/change/do when you cleaned off the excess compound?

I looked up the datasheet and didn't see where it said that

have a look at the pic of the device.
The legs/pins will be coded. A note will detail which code belongs to which pin type (G D S).