That's a big help - thanks!
So, from the "7K" resistor I conclude that it is carrying about 33mA, and the "182" says the 5965s are carrying about 10mA. These are reasonable numbers, and validate my use of PSUD2.
Output stage:
My calculations predict 453v at the plate of a 2A3 carrying 60mA. This is 53 volts higher than the manual, because the PGP8.1 produces more voltage than the deYoung which was in the original Afterglow. The target for a 2A3 is the value in the spec sheet, 250v plate to cathode at 60mA, leaving 203v across the cathode resistor. Now the driver DC current of 10mA goes through the 2A3, leaving 50mA for the cathode resistor. The revised value should be 4060 ohms. The closest 5% value is 3900, and you probably want a 25 watt or greater rating. The bypass cap of 220uF should have a 350v rating, rather than the 200v originally specified.
Driver stage:
We now have 153v at the plate of the driver, not the 100v of the original. From the 5965 data sheet, we can see that a single triode with 3v bias and 150v plate to cathode will carry 5mA, so two in parallel will match the 10mA provided by the current source. That is easily done with a 300-ohm cathode resistor replacing the 182-ohm original. And at the peak AC driving voltage of 45v, the bias margin is still 1.3v - not Buddha's ideal of 2.0v minimum, but my measurements some years ago found that a 1.0v minimum is probably good enough. So you can retain the 5965s as in the original design.
However, your current 5965s are nearly dead - in your current amp, they should be at 100v on the plate, but you are measuring 168.3/219.6v. Replace them! (Your 2A3s might also be tired; we'll be able to tell from the voltages after you have made these changes.)
The Plan
Well, what I would do anyhow :^)
* replace each 100uF power supply cap with two 220uF/350v in series and matching resistors as already suggested
* Replace the 7K resistance with 3900 ohms 20+ watts
* replace the cathode bypass with another 220uF/350v cap (for two amps, that's 10 caps total - enough to get a tiny discount!)
* Replace the driver 182 ohm resistor with a 300-ohm resistor (1/4 watt or greater)
* Get a fresh pair of 5965 driver tubes
Of course, this is a prediction - so check all voltages again after this is done; we might need to adjust a few values ... :^) Theory is wonderfully powerful, but it's still not reality!
Once it is working, I would strongly suggest that you monitor the driver plate voltage (the 2A3 grid, pin 3, is a good place to check). It should be close to 150v. When it goes over 175v, it's time to replace the driver tube. Note that a new tube may have a high voltage at first, and drift down, taking as much as 100 hours of operation to get to a stable value. Once stable, an annual check is probably good enough.
