I recently acquired a Collins 310B-1 that I would like to put on the air.
After repairing the AC input circuitry (blown feedthrough cap, etc.) and
replacing the elecrolytics, I found the power output was well below the
rated 15 Watts so I started looking at the signal chain.

What should the level of the baseband signal coming from the 70E-8A PTO?

Measured at the grid of the 6AG7 first buffer multiplier, mine is only 4V
pk-pk. That is not enough to run the multiplier class C because the cathode
resistor develops 12V when the 310B is keyed. On 80 meters, I get 40V pk-pk
out of the buffer multiplier measured at the grid of the 2E26 power amp
giving a multiplier gain of about 10. Since the power amp has a grid bias
of -60V, the drive level isn't sufficient to operate the amp class C either,
and there's no grid current for tuning the buffer stage.

I haven't yet measured the value of the 1.5K cathode resistor of the buffer
multiplier, so I don't know if it has increased in value.

Thanks in advance for your help.
Bob AD3K