[Heathkit] SB-1000

[Charles W BWW Burkhardt]

Gentlemen- A problem ( I think ) with my Heath SB-1000 amp. Some time ago
the group helped me repair a bad grid circuit-including a resister on the
metering board, the bias zener and even the meter. I've been limping
along with the unit (don't really use it much), but would like to get it
in good working order. This unit has a single 3-500Z tube and is supposed
to require over 50 watts of drive to reach full output. When I use the
thing I have to keep the drive cranked way down. If I try for more than
about 300 watts the main fuses blow. This is into a dummy load, or a yagi
with low SWR. Grid and plate current seem to be where they should be but
the plates on the tube become bright red on CW which doesn't seem normal.
I'm wondering if I'm fooling myself and the tube really needs to be
replaced. Any ideas? Thanks, Charlie, K0GPF