I totally eliminated the hum with a jumper between pin 1 and pin 8 of PC5. I have no idea why that would eliminate the hum but it did. The preamp is dead-quiet now. I'm sure there is some problem in the original wiring by the kit builder that makes this jumper do what it does but I can't find anything that seems wrong other than that twisted pair issue.
The Pas is oem except for Roy's 1st level power supply and new caps/tubes and I want it to function as original with all filters/switches/tone controls. I have ordered a new jack board and volume control for it but for now that will be the extent of the changes.