B-52 AT-100

[livewire]

B52 AT100 came in dead. Have repaired output tube circuit, open resistors on board, and also power indicator lamp circuit. 2 open 100 ohm resistors also open, also 10 ohm in close proximity open also. A large wirewound on power supply board came out also. Output tubes replaced, all other tubes are ok. Correct voltages all present now. The amp runs now, clean channel works fine, however, overdrive channel has very little volume. There are no open resistors in the circuit, all components appear to be ok. Anyone have any experience with these? Am I down to connections at this point? Many thanks in advance..

[xtian]

No experience with this B-52. But sounds like an opportunity to trace a signal with a scope from input towards output.

If you don't have the tools, you might at least divide the circuit in half if there is an FX loop.

[The Dude]

Agree with the above. Signal tracing would be best. Sans that, try tube substitution. Check that filaments are lit. Check plate voltages on preamp tubes to be sure you don't have an open plate resistor.

[livewire]

Well, turns out R-9, 10 meg which feeds grid of V1-2 open. burnt open track underneath tube socket.
Thanks for the replies guys, the more opinions the better, I always say..

[Jazz P Bass]

Hmm.

Not doubting you but that 10 meg R9 goes to ground on the Ch 2 signal path, directly after the Ch2 relay contacts.
How does that resistor being 'open' cause the Ch 2 signal to be lower?

B52 AT100.zip