Thanks for all the responses.
Elevick, "blow" may be a poor choice of words -- more like "fail" or "short." Definitely normal; the manual even reads:
"If an output tube shorts, this circuit will turn off the amplifiers main power supply by tripping the front panel circuit breaker, and light a red LED to indicate the defective tube(s). If this occurs, simply replace the indicated tube(s), reset the fault indication circuit (turning off any lit red leds), check the plate fuse, and rebias the amplifier."
Both amps were just serviced at c-j.
B.