I have a working MKIII amp fitted with a low gain VTA board that is all biased up nicely. I am concerned because the B+ on the VTA board is reading 500V DC and all I have read says that it should be 400-440V DC.
I have since changed the resistor on the quad cap from 6.8K to 10K as I believed this should drop the voltage but it has made no difference. In fact there does not seem to be any voltage drop at any stage of the quad cap. Should I expect a voltage drop and if so could the quad cap be the problem? If not what can be used to drop the B+ to be in range? The transformer vibrates slightly if that is any clue.
Many thanks for any help you may provide.