I should be able to get back to it in a couple of hours. Only just got
around to building a Dexion support frame so I can toss these sorts of amps
around with gay abandon, and not risk the bottles.

The valve set that are in here are all 2009 , he took out the new ones and
replaced these used ones. They look brand new except for simple dragon's
teeth marks, ie not repeatedly moved around.
The Russian markings are quite visible and there is no sign of overheating
of the bases , still light brown , and the pcb around looks as new.
But the first thing I will do is check for o/p bias drift, then heating the
pcb with hot air and a 2Gohm megger and then remove V1 and see if hum
returns then replace and monitor DCs around V1 on heating ,

No mention of that Marshall Forum page about hum but it could be these pcb
problems around V1 the immediate problem