Tom,
My tube sockets are located a bit further from the original position than yours.
I started chasing the hum right after I fired it up the first time. Biggest culprit was a ground wire that wasn't too well soldered.
Fixing that helped but the hum was still there.
Since I'm using physically large cap's in the tube heater circuit, they had to be mounted of board. I replaced the wiring to these with shieled wire and tied back to a star ground.
Next I started replacing signal path wires, including those to the tube sockets, with shielded cable. All the shields are tied to a single point on the PCB. Again, an improvement, but that @%^%^@ hum was still there. Hum at this point was audible with headphones turned up with no signal.
Then I found the final culprit, V3. The tube itself was the source. I replaced it and the hum was gone. Might have been a poor connection or crud on a clean looking pin. But it is gone.
Put in a new V2 and V3 tonight and all remains good.
Make sure all your heater wire is tightly twisted, double check all your ground connections, and clean the pins on your tubes and/or try replacing them one at a time to see if tha makes any difference. Hum might also be induced from your turntable. Try moving the Cornet and see if a change in orientation has any affect.
Good luck and have patience.
Bobbi
