How to tell if the Valves need changing in a 2nd hand amp

Funkfingers

adampeter said:

Marshall jubilee 2525c

If the Mini combo is anything like the original issue 1x12, one of the valves will be a pig to access.

Maynehead

Just to mention, you have two completely different manufacturer power valves in there, with different internal structures, which is unusual for a matched pair, but I guess possible.

Again, that’s not what’s causing your issues, but it’s an interesting observation.

Moloch

Update: Tech has been round to collect it. Had me give it a couple of bangs on the top to see what would happen. First brought all the volume back to Green channel. Second brought it all back to Green and Blue. Red was, as ever, fine. So, looks like a loose connector or dry solder joint and the tech says he's confident than repair will be covered by the intial £40 fee. So, a lot better that it could have been!

Cheers for the input, lads.