Fender 700 Roc pro reverb Humming noise

[Jam]

when I turn up the reverb up it gets a loud hum and when I unplug the the reverb tank it dont hum no more I dont where to start to look? Thanks

[Jam]

Hums when I turn up reverb

Is this a ground issue?

[Jazz P Bass]

Roc Pro 1000 reverb Circuit

Any chance the input & output cables are reversed at the reverb tank?
As to a ground issue, neither cable attaches directly to ground.
Unplug one cable at a time & see what that does to the hum.
I have attached the reverb circuit schematic.

[Enzo]

Look inside the reverb pan, is one of the wires broken off at the OUTPUT jack? or does the OUTPUT end measure open on an ohm meter?