Egnater Rebel 20- velcro noises

[Cups]

Hello friends
Have an Egnater Rebel 20 on the table doing the weird velcro power tube noise, but only after 40 minutes or so.
measurements:
385vdc on all plates (has a pair of el84 and 6v6)
375vdc on all screens
-35vdc on grids of 6v6
-16vdc on grids of el84
(this one is weird) 3.3vac on heaters

Had the common 470R resistors on all screens. Had the amp upside down and had to push up and take apart the ouput jack pcb to do the measurements and the chassis was hot to the touch. It would start with the velcro noise and then I'd take measurements and it seemed to settle down.

I have to take out the power tube pcb to read traces because most of them are underneath. This is not a serviceman's type of layout.

Thanks for any advice.