Tracking down a hum.

Thanks for the responses. I swapped tubes out and powered up the system, same result. Looking at the capacitors, they all LOOKED okay (no bulges or anything). Their are no capacitors in the external power supply so it's something under the hood. Either tube heaters or a bad capacitor somewhere. Fortunately this should not be a prohibitively expensive fix. It goes to the shop tomorrow.

@imhififan  I have swapped out tubes, the condition still persists. I connected my headphone amp to the power (briefly) no hum coming through that I could hear. So I think it's in an output capacitor or in the tubes heaters. It isn't the tubes themselves. 
Thanks for the advice.

Post Script to all this.
I took the amp to a shop for repairs. The techs (2 of them both experienced) could not find an issue. Told me everything in the amp is "up to spec". Gave it back to me no charge. Get it home hook it up and the hum is still there. Only now it is constant. I call Rogue. They say try the dip switch in the voltage regulator. I found it and switched it from H to L and now everything is fine. Hum is gone amp runs nice and quiet. If it happens again. I'll send it off to Rogue.
Thanks again to everyone for your input.

Curious about this H/L switch in the regulator. The only one I can see, and the only one in the manual, is the phono board gain.

Mine is a line stage. Look for a small orange and white switch it's upright and small, near the transformer.
I was able to find it without too much trouble