Smoke on my power amp

in the specific case of tube amps having output transformers

Fair enough!  (But we were talking SS...)  Also that is more an issue of disconnecting while playing, rather than "turn on with no load" - which are quite different.

Ihcho,
Have the transistors been destroyed? It’s really grainy from the photos;

Since many of them are connected in parallel they all experienced significant current ( if actually shorted at output), but due to device tolerances, in the event of a short, the devices and emitter resistor combinations with lowest resistance will go poof the fastest; the emitter resistors on all output transistors of the compromised channel should be checked as well because even small changes there can really affect the distortion profile of the output stage.

If this were my amp and such a thing happened I would probably end up rebuilding the output board; Pain in the ass yes, but then you have a factory speced unit once again.

Did you examine the speaker connectors for evidence of arcing ? Black carbon, deformed metal etc...

In your city of Saginaw there is an excellent technician at Gratiot electronics- he can fix your amp quickly and fairly priced. 

I  have had Tim at Gratiot fix all my amps when needed-including Cary, Grommes, and Plinius (many years ago) Very capable on high end repairs.   

Thanks masaja415,
I did not know about them.
I contacted them yesterday. They seem to work on high end audio gears. It is pretty close to where I live. I will give a try.
Huge saving for me if they can fix it.