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