problems with original wad 300b

[julianr]

Hi
I made one of these for a friend and it has worked great for 10 or years, only things done have been to change the 300bs a couple of times and change the 5687. Anyway it looks as if one of the 300bs have gone - the cathode resistors on one side are measuring 67 Ohms instead of 1.2K rest are ok, the amp got very hot and the gz37 glowed cherry red - he put it off immediately.
With all the valves in except the 300bs voltages are good, and the amp does not draw too much current. When I put in the 300bs and start up with a variac as the heaters kick in the current shoots up and some of the 300bs get very hot - presumably the one that doesn't is the blown one.
Is it possible that anything else is wrong. I have got it home now so can test it more fully.

thanks Julian