I have a 65 Bandmaster that I've had for ages, but have never had the vibrato working.
I've checked the footswitch and that seems fine. When I look down one of the input jacks I can see a Valve (tube) pulseing, the speed of which changes coresponding to turning of the "speed" pot. The sound does not change however, I get a clean signal like the "normal" channel.
It had a complete re-valve about 2 years ago.

Any suggestions very much appreciated.

Mike.

p.s I last switched it off on Tuesday. Is it safe to put my hands in there yet??