BF Bandmaster Vibrato 'motorboating'(?)

[pdf64]

Are you sure that the HT caps are good?
The particular grounding scheme used can make a difference; it's a good idea on such an old amp to re-establish all fastener based 0V - chassis connections, eg pots, jacks.

[lowell]

I did make sure the HT caps were good. I replaced the main B+ caps as well as they were original. As I just simul posted with you, the wires to the socket had a HUGE effect on the noise.