Tube failure -- what would happen in worst case?

Did you replace the tube, Bill? Check fuses? Bad cord or problem with wireless xmitter? Rectifier problems? I don't know a lot about this stuff but,I'd check the common failure parts before taking it to the tech shop. Might be an easy fix you can do yourself. Also, it will save you some cash and embarrassment (believe me, I know about embarrassment)!!!!

I noted in another thread that I've been using and abusing various tube guitar amps since the 60's and, since 1968 anyway, no tube has blown up.

Self biasing or not, the problem comes when a cathode to anode short happens in a power tube. The least damage is blowing a fuse in the amp. But for me, the cathode resistor gets fried immedately and needs replacement. This also happened on a current source tube (CARY Rocket 88) and I had to replace that resistor too - I knew it was bad and asked mfr for the value, but they gave me the wrong resistor and I had to send it in ($60 bucks each way).

So it is a pain. But the moral is this NEVER EVER leave your house with tube equipment powered on.

Cathode to anode shorts are very very rare, and the sort of thing that should blow a fuse without damaging anything else. If not, the manufacturer has not thought things through.

I leave tube equipment on all the time. However, its tube equipment that I know is designed to not get in trouble if a tube fails. No blown cathode resistors, maybe a blown fuse. But in truth I have yet to have that happen despite using such amplifiers for over 35 years.

That's not to say that all amps are safe like that. The Fourier amplifiers mentioned earlier were prone to spectacular failures as were certain ARCs (when they were sold a bad batch of Cornell Dublier filter caps back in the 1980s).

I friend had flames coming out of the top of his power amp do to a tube failure. I'd be more worried about the house burning down than damage to a component.