Kel34

G'Day

Last night flashed up my kel34, got a hell of a crack sound what is this? power supply caps failing dried out?, sudden short or valves. Still have sound but with a load of noise can't really describe the sound of it.
This amp was rebuilt a couple of months ago, renewed all the components everybody advises on this site apart from the power supply caps so hence my thinking. Just measured up all within spec, any ideas.

Regards
Bruce