Capehart 325 restoration

[robert1]

Originally Posted by bandersen

The 6W4 tested OK but I replaced with a NOS 6AX4 anyway. Replaced the fuse too. That got HV back until I tweak the drive control when I got a flash and the fuse blew again. Still not sure exactly where the flash came from. Might have been the fuse itself.

Before it died I managed to test the HV and it was only 6.5 kV - should be closer to 11 kV. Something sure isn't right in that circuit.

since i don't have a diagram to look at for that chassis, i could only ask a couple of things. is the horizontal drive control a adjustable coil?, or a variable capacitor? or a pot? if it is a coil type, usually, those have a capacitor across it. it might be leaky. the coil itself, may have shorted windings.

have you checked the current on the cathode of the 6BG6?

i still suspect that red disk capacitor underneath the damper tube socket.
it appears to me that something is drawing too much current in the output stage. it might be that the flyback xfmr may a a few shorted turns or any of the above mentioned things, it also could be caused by a problem in a different circuit protected by that fuse.