Well, that’s good news.
I should mention that there is a lot of inertia behind the idea that replacing the selenium diodes is mandatory. Although I do not generally disagree, I’m not sure how urgent it is if the 12AX7 filament voltage is in-spec per the original PAS-3X manual. If it is in-spec, the filaments should still be checked with some regularity, but this is not a guarantee you’ll catch it in time if the selenium stack fails.
In order to accurately determine if the filament voltage for the 12AX7s is in-spec or not, you need to be able to establish the reference AC line voltage with a variac, so that you measure 117 VAC across the power transformer's primary winding with your meter (don’t rely on the scale on the variac itself). But, it just might be possible that later versions of the PAS might have power transformers that were wound for 120 VAC, so a little experimentation might be called for. Offhand, I think a good way to establish a reference AC line voltage is to set the variac so that you measure 335 VAC at pin 1 and also at pin 6 of the 12X4 (although this is for the B+, it might be the best way to know that the proper AC line reference is established). You could also look for 10.5 VAC between pins 3 and 4 of the 12X4, though this might not be the most reliable method if there is an issue with the filament circuit or even with the pilot light.
Wouldn’t it be easier to simply replace the selenium stack without having to go through this rigmarole? Replacing the selenium stack is a little more complicated in the PAS compared with, say, a Stereo 70. When you replace the selenium diodes in a PAS, the 12AX7 filament voltage might run up too high because the replacement diodes will most likely have a lower voltage drop than even new selenium diodes would. If the filament voltage goes too high, it could affect the sound quality in ways you might possibly not like and tube life could be shortened, too. What you would have to do is to experiment with installing one or two small value resistors in series with the filaments to get the voltage right, which can be a tedious process.
So, replacing the selenium stack in a PAS is not that simple. If you decide to delve into it, I suggest starting with a 5 ohm resistor in each leg of the voltage doubler and see where you stand, again, always referenced to the voltage table in the Dynaco manual. A 2W power rating could be okay for the resistors, but measure the voltage it is dropping and calculate the power dissipation to make sure.
If the selenium stack is presently failing, then it is something that should probably be attended-to ASAP.