Troubleshooting help needed - Fender DRRI

[longislandrod]

I have a Fender '65 deluxe reverb reissue that's developed a 60 cycle hum. I'm wondering if anybody has experienced this and can lead me in the right direction to repair it.

Symptoms. Hum is ALWAYS present at a low volume with nothing plugged into the amp. It is also present when the guitar is plugged into the amp, in either channel normal or vibrato. The hum get louder when I turn up the reverb volume without the reverb foot switch plugged in. With the reverb switch plugged in and the reverb turned off the hum does not get louder when turning up the reverb volume. It also squeals for a brief moment when turning on the stand by (may not be related).

I have already swapped out all tubes with new ones - no change. I have also disconnected the reverb tank, also no change.

Any clues to help me troubleshoot and fix this? I have a schematic and service manual.

Thanks.

[Wayne]

Not familiar with the circuit, but just shooting from the hip - cables to/from the reverb tank?

W