Quote:
Originally Posted by MT70B
old_tv-nut, Your are correct the schematic is very blurry. R60 which is connected to B+ is 60K and R58 which is connected to the plate is 10K. The balance control is a 1 meg pot and coupled between the R60 and R58 resistors by a 100K cap. Since the balance control is DC blocked it only affects the signal and not the plate bias. This along with the fact that C77 (a 10K cap) couples the signal directly from the plate on to the next stage is what is perplexing.
Mike
|
OK, so the effect of the balance control is to parallel a resistance between 1 meg and zero across 60k, so the parallel value goes between zero and about 56 k, and the total plate load goes from 10k to 66k. This will change the gain of the amplifier stage, but calculating how much it will change also requires knowing the triode plate resistance and the impedance of the following network.
Can you measure the resistance from one end of the balance control to ground when in stereo mode to verify that the wiper contact is not open?