Rockola 442 Hum

So far I've recapped my 442s amp but still have a low level hum that seems excessive. It's there from switch on and doesn't appear related to the volume control. I'm wondering if the PSU could be an issue, but it seems on my model the filter caps are in the amp. The only caps in the PSU are lower value ones. Any thoughts on what may be causing this problem? Failing rectifiers or diodes? Any advice on where to go next would be useful.

I do plan to check all my amps resistors but not sure if a resistor could cause the hum? I'd assume "noisy" resistors may well test within tolerance on a multi meter?

I have run into a hum problem on RockOla's that was caused by the "free grounding" ( "earthing" to you ?) wires ( Usually green/white, or green/yellow), being poorly connected, or "dirty" somewhere inside the phonograph. The "common" grounding post area is most suspect--check there, and also, the nut holding all of the wires MUST be brass ! Ron Rich