This is on an Ampeg VT-60 amp. Here is the schematic:
https://ampeg.com/support/files/Sche...SCHEMATICS.pdf
It was the main AC fuse F1, a 2.5 Amp Slow-Blow fuse, that was blown open.
Then I noticed the single 12" 8 Ohm speaker, was incorrectly hooked
up to the 16 Ohm output. Was this possibly the cause of the blown
fuse?
Some people on the internet, feel that with tube guitar amps, the
impedance of the speaker is not as critical as it is with solid-state
amps, and that the main danger is to have a no-load condition (an open).