by mesherm » Wed Oct 01, 2008 1:43 am
From J3 and J4 terminals 4 and 5 should go to 300B pins 1 and 4. terminal 3 for J3 and J4 should be connected to 300B pin 3.
The lead from the output transformer marked 2.5K or whatever OT you are using should go to 300B pin 2. The other OT lead probably marked B+ should be connected naturally to B+.
Check the diodes D1 to D8 to make sure they are oriented the right way.
Also check capacitors c11 to c14 to make sure the polarity is right. Sometimes when you install components on the opposite side of the PCB to flush fit into the chassis you can accidently reverse them. Same with tube sockets and their numbers. I have made that mistake a few times myself.
Measure the voltage across and of the three R15 or R16 resistors to check the self bias voltage on the 300B. You should be getting around 65-70 volts.
Double check that R7 and R8 are both 270k (270,000) ohms.
300Bs would be happier if R9 and R10 were 200K but 475k shouldnt cause the problems you describe.
Check R18 to make sure it is 10K brown-black-orange.
I assume you are using 5 volt filament trannies for the 300Bs, make sure the center tap is not connected if you are going through the GSG PCB since the filament grounding is handled on the PCB.
You must be using a separate 6.3 volt filament supply for the 6AX5 and 6SL7. Have you made sure that the traces are cut on the PCB to separate them from your 5 volt 300B supply?
Also what part of the country are you located?
Mike's N-1 Rule: When looking for N number of components to finish a job, you have a 95% chance of only finding N-1 of them.