Thanks for the questions, here's more info and I've attached a pic.
Tubes:
4 JJ EL34; 1 Sovtek 5AR4; 1 JJ ECC82; 2 SED-EF86 Winged C
As a note, I have replaced the JJ with Ruby EL34's and the hum is louder.
When I first built it, I had to replace the 10 ohm resistor that went from the EL34 socket to ground on the right channel, since it was dead - no burning or physical damage.
I've examined all ground connections and can't see any cold solder joints or other issues.