Amp tech has given it a complete going over - all is as it should be apparently.
Going to give it a new set of valves as it's 5 years old - then I'll have some spares at least.
Thanks for suggestions.
(Newb first post)
My Nomad 45 has developed an annoying (but not loud) mains hum on Channels 2 & 3.
Pre-amp valves have been checked/swapped - and it's still there.
Any help gratefully recieved.