I've had some small hum on both channels that was constantly present. It was not linear with using the volume potentiometer, just a constant 60hz hum that was really distracting. I searched and found lot's of forums talking about ground loops and nothing really actionable on fixing the issue.

I finally fixed the hum today and wantd to share the good news. I replaced the wires to the output RCA jacks by using shielded cable from eyelets 14 and 7 on PC-5 to the right and left outputs, respectively. Also, the RCA jacks were grounded to the chassis and to eyelet 8. I removed the ground from eyelet 8 too.

Now, the hum is gone and sounds wonderful without that distracting hum.

You did, indeed, have a ground loop. That ground wire erroneously twisted around the output signal wiring was groundlooped due to the common ground at the linestage board. There is not supposed to be that twisted white ground wire around the output signal wiring; any hum induced in that undesired ground loop would have radiated directly into the output wiring and that's apparently exactly what was happening in your PAS.

gp49-unless i misread curcio's selector switch instructions-twisted pair left and right to preamp eyelets 7 and 14 respectively -grounds to 8-i have hum -never had it in a pas--along with i used roy mottrams i/o board and the resisitors on the i/o are omitted-with that combination there is no ground at all to the i/o board-incredible hum--with the 10 ohm and 510k in place-still hum -i jumpered from i/o ground to chassis and all was quiet-i see now why--my point is conflicting instructions-i think what joe and roy have in mind works with their total upgrades-but not if you are keeping original style boards-sooo!! put the 510k and 10 ohm in place unwrap the ground wires from 7 and 14 and run ground to eyelet 1 from i/o board--per original dynaco instructions howie