[murphyv310]

Hi Dom
As Steve_P correctly says it could be a damp LOPT, I would put it somewhere really warm and while waiting for it to "cook" go through all the waxies and check those 20% resistors.
I cooked mine for six months on the top of the boiler and Wow what a difference, I did another in the oven and WD 40 and all sorts of other things and it worked fine too.
Good luck with the set, they are crackers when ok, I wont get too involved though with this thread due to work commitments this week.