12-22-2018, 02:57 PM
I repaired on of these with the same hum. It was the rivets to 77 tube shield base. I drilled them out and used 4-40 screws with star washers and nuts to replace the rivets. No more hum. The 77 tube being a detector and 1st audio tube makes it susceptible to hum. Plus the audio runs full tilt to the 42 as there is no audio volume control.
Tony
“People may not remember how fast you did a job, but they will remember how well you did it”