Looks as though the hum was associated with the input socket. This is
designed to be isolated from chassis taking ground from screened lead. As it
was turning round with tight bush nut I assume someone had been in there and
changed the insulating bushes about so ground-looped, now isolated and tight
and no undue hum.

Looked under the pa board and it is 2 seriesed 47uF,450V for HT1 and the
other one with a dropper for another HT.
date 2003 or later.
Mains primary now set for presumably 250V as heater readings are still a bit
high.
So with full mains on there and all 8 12AX7 and only 4 of the 6 off 6L6
reads quiescent 6.6V ac and 470V HT1 from 356V ac, other secondaries or/or
32.8V ac and bu/bu 66V ac.
Incidently not only the neon /sw needed attention but the handle is crap
and jagged sharp metal exposed inside, covered with nylon spiral wrap, then
expanding nylon sleeving and then 2 layers heatshrink all under the covering
now


--
Diverse Devices, Southampton, England
electronic hints and repair briefs , schematics/manuals list on
http://home.graffiti.net/diverse:graffiti.net/