I am working on my sons amp which blew up with a loud bang. What
I have found so far is one tube with a grid to cathode short
when filament voltage is applied. I can see that this would short
the bias out but I don't think it would cause the bang heard
when it failed. At the time of the failure there was the smell
of resistor overheating but I haven't found it.
Could the shorted tube be the result of a parasitic osc and
not the cause of the failure? If so I guess that would explain
the loud bang. The plate chokes seem to be OK. There are two
of them in series and the physically smaller of the two has
seen heat but I don't think it has failed. I believe I'll
pull the parasitic suppressers and check the resistors also.
If any one has some ideas I'm open to suggestions.
Thanks and 73