some pernicious stuff going on and may have been associated with some of the fuzz one heard on the ham and SWL bands.
Hmmm. The reason I was able to lay hands so quickly on a 12CL3 was that I had just been measuring its envelope diameter to assist in chassis layout. When it's all fired up I'll have to poke around carefully to make sure the switch-off transients aren't ringing the mains transformer.