On Thu, 25 Feb 2016 23:48:16 -0800, jurb6006 wrote:

Are the chopper transistors getting hot ?

The main chopper is a TO-3 cased BJT with a closely-finned heatsink
bolted to the top of it. By the time the resistor starts to emit a
scorching smell, the chopper hasn't even had the chance to get barely
warm.

Did you actually check the resistance of that resistor that is getting
hot ?

Yes, it's exactly 20 ohms as specified. But please don't ask me to do any
other checks for the next few days as I'm staying over 300 miles away at
present.