Thank you Ray (Rawinsonde). It was a pleasure and glad you're back to enjoying them again.
For those interested, these amps have hybrid rectification for the high voltage supply which consists of a single 5AR4 tube and two diodes configured as a "bridge" rectifier. The two diodes were shorted, thus shorting the transformer's HV winding to cause the fuse to blow. The filament supply is exclusively A.C.
Ray had a multimeter, took various measurements, bought replacements from Radioshack, soldered them in, done, except....... now the other channel no longer worked.
Ray performed systematic troubleshooting and found that his other amp was the culprit with a non-functioning rectifier tube - possibly caused when swapping tubes into the shorted amp early on. He had several used 5AR4's on-hand, measured them initially for shorts (one was), then tried the remainder in the amp until one yielded a working amp (two did not).
Well done, Ray!