Scott,
Thanks for getting back to me. The resistors that make up the voltage divider are R8A (1k) and R9A (100k). They are located under the output jack, so you’ll have to remove that to access them. Look in the troubleshooting guide to see how to properly remove the jack.
If the pedal that you put after the volume pedal to reduce the volume level was set to unity gain, you might be able to measure the resistance of its volume knob to get an idea of what the voltage divider resistance values should be. Otherwise, you can make note of the signal level change by using an oscilloscope.
With tube amps, the preamp tubes don’t usually offer much tonal change between loud and soft volume levels…this is because they are able to handle a lot of head room giving a relatively clean tone. The real tone (increased odd harmonic distortion) comes from pushing the power tubes hard…but the volume level from the speakers usually gets really loud before they really start sounding good. This is why “power brakes” are used…to attenuate the already distorted tone from the loud power tubes. In your application, you were just attenuating the hot preamp signal, which has too much voltage headroom to break up nicely, while leaving the signal getting to the power tubes relatively low. Since from a tonal perspective, it doesn’t matter if the preamp is turned up or not, I suggest leaving it relatively quiet, so the signal hitting the volume pedal is lower. This way, it won’t bleed through as much when in heal down position.
I hope that makes sense.
-Brach