800 circuit power section hum help!

[joesatch]

ok i have tried many things. currently i have both preamp tubes removed and the input to the P.I. from the master disconnected.  reservior cap is grounded to chassis along with the PT CT and power tube grounds.  Heater is artificially grounded to chassis with two 100R resistors (i have tried removing this as a test no difference).  B+1 grounded to chassis along with bias ground, OT ground, presence ground.  With the master connected to the P.I. i get good signal and preamp section works fine but the hum is there.

[AlNewman]

Sounds like you have your thumb on the input cable.

[HotBluePlates]

... currently i have both preamp tubes removed and the input to the P.I. from the master disconnected.  ...

What happens if the Phase Inverter tube is removed?

[joesatch]

noise goes away if the PI tube  is removed. this is 60 cycle hum correct? so it's in the audio path?  PI input is disconnected.

[mresistor]

Sounds like 60hz to me. Check all grounds for good connection.  could be injected into signal via a problem with small bottle tube.  So have you substituted all the tubes?

[joesatch]

i pulled the board. i believe it's conductive. built too many amps and this is a simple circuit. must be the board. i'll put a turret board in

[joesatch]

 

[danhei]

i pulled the board. i believe it's conductive. built too many amps and this is a simple circuit. must be the board. i'll put a turret board in

Why do you believe the board is conductive? That doesn’t seem particularly likely for what appears to be a fiberglass/epoxy PCB.

[joesatch]

entire bottom of the board has a ground plane around all holes

[pdf64]

entire bottom of the board has a ground plane around all holes

Are you using it as a shield, by only making a single connection between the chassis and ground plane, or are you using it as a conductor for 0V common, with 2 or more connections to it?
Whatever, the likelihood of a good question board substrate becoming conductive seems low, much lower than other possible causes of hum.

[joesatch]

spent too many hours troubleshooting the hum. i ripped the board out will build a turret board over the weekend and be done with it