Pro jnr red plating

bandmaster188

My mates pro blew the internal fuse last night. We changed fuse, fired it up and within a minute of playing the amp sounded terrible. Checked the back and one of the 84’s was glowing brighter than the sun. Is this just a shorted valve or something more sinister?
cheers!

ecc83

Almost certainly just the valve(s). You could have a leaky coupling cap or a short cathode bypass cap but I think such happenings are now lost in the mists of time and Hunts capacitors? Sprague were not good either.

Dave.

ICBM

If it's just one valve, swap the power valves round - when they've cooled down! - and see if the fault moves with the valve or stays with the socket. If it stays with the socket, turn off ASAP or you'll cook that valve too (it's still useful as a spare at the moment) - the fault is most likely a broken connection in the grid path to the valve, which also carries the bias.

bandmaster188

Cheers fellas. I’ll get him to check it out.