OK, so I bought a trashed Dynaco St-70 from this guy on craigslist and rebuilt it from the ground up. I have added new tube sockets, can cap, bias supply, tubes, choke, power transformer (Tomiko toroid), new output trannies (Tomiko), and a new board I got off the bay (China) that uses the 6GH8 tubes. With no input hooked up there is only a slight hum, but as soon as I hook up an input, there is a very very loud hum that is so loud that I quickly power off the amp out of fear of something bad happening. I have already tried two different new can caps, 3 new rectifier tubes, and checked and double checked all solder connections and made sure everything is wired correctly.With no input connected, if I as much as run my hand next to the input I get a loud hum. I am at my at the end of my rope with this thing and would really love to listen to it!
Ok so it really is only the right channel that hums, also with both input tubes removed, the amp is dead quiet. I am going to replace all the resistors on the board just in case and maybe the coupling caps.