@elliottbnewcombjr Yes I meant to say KT150, that's what I have.
I have rebiased all the tubes.The hum is present with the preamp off. I used the DB meter from my phone and tracked the loudest reading and it is coming from the back of the amp. I have also changed the power cable, and I just tried plugging it into a different socket. I checked the speaker cables. I have used all this equipment setup with different amps and they are dead silent.