Traynor Bass Mate YBA-2B 120 cycle hum

[Helmholtz]

The 6M resistance looks like a carbonized/conductive socket which might cause arcing at high voltage.

[misterc57]

I did a deep clean of the socket and reading is now open. Reconnected the OT leads and all is working fine. Plates are seeing 407 V which seems high but schematic says 395 V.

[Enzo]

Well 3% high is not something to be concerned over.