[sexton_mallard]

Thank you Techman and PJL. There does indeed seems to be some very unstable caps in this set. On switch on there is a disconcerting cracking/rustling from the speaker even before the the valves warm up. I have already swapped a few caps around the EL84 already. The 50mfd cathode electrolytic was actually getting hot the last time I had the set running when I was measuring HT! The mains electrolytic is developing a hot spot and has a stalagmite of dried electrolyte on the end where there is normally a plug or rivet in the top of the can. The wiring and valve sockets seem to be quite fragile.