1974 Super Reverb C.S.A Thermal Protector

[bobloblaws]

Mains draw? Use an AC current meter - an ammeter - in series with the mains power. One could use a metered outlet on the bench. Any well equipped shop should have a switchable outlet with a current meter, usually associated with a variac. But one could be easily made with a current meter and some temporary wiring. Most hand meters have AC Current scales these days. Clip such a meter in place of the fuse in the amp fuse holder.

Right, I've noticed "The Guitologist" having a meter on his variac, in fact I found this video where he shows what meter to get and how to set it up etc.

https://www.youtube.com/watch?v=2mrlha-uzro

I think I will order one, I already have the variac. In the meantime hooking up my multimeter via the fuse holder sounds like the most practical method.

[bobloblaws]

Is your heater voltage holding up?

I don't know what you might expect to see in the event of an actual PT issue, but in any event, it is holding steady at 6.5V.

It's not uncommon for transformers to run on the warm side. That said, have you checked bias? Maybe you're idle current is high? What is the amp's total current draw at idle?

So as I said, the bias is running fairly low, about 20mA per tube. The current draw in standby mode is about 0.480A. In play mode at idle total current draw is about 0.750A.

So I think we can safely assume that either the rectifier failing took the thermal protector with it, or that they failed more or less coincidentally. Everything seems to be running normally with the replacement rectifier. (That is, assuming those current draw readings are normal. Given that the fuse is 2A I'm making that assumption.)