SF Twin Reverb power transformer: how hot is too hot?

[Chris D]

Hi all. Too late to be any use but, just out of interest, these are some measurements from a working 1976 SFTR. It’s a 100watt export model with master volume and pull switch. That’s a CBS 100watts by the way, or 85watts rms at 5% distortion in the real world.
Caps are new, tubes are a newish matched set of TAD 6L6GC and bias is 15watts per tube. Power transformer is a Schumacher 022 764 and you really wouldn’t want to keep your hand on it for more than a few seconds except for a bet.

[22uf]

Apologies for the necro but this thread was very helpful when troubleshooting my 73 100w master non push pull with a Schumacher PT.
It operates at a 55c and I was very worried but based on the above post it seems to be a thing for these old lumps ..
Just wanted to add that I had thermocoupled mine and monitored it over the course of a few hrs at more or less bedroom volume.
55c peaking at 62c. Too hot to touch.

All voltages and bias are quite normal and every tube is brand new and tested OK.

The chassis looks like its been baking for decades.. and it likely has.

Evidently no cause for alarm. 48 years of working .. looks like its going to keep on working..

Hopefully this is useful for Google/posterity.