I replaced some of the 12ax7, & got a new set of EH6973 tubes. This greatly improved overall stability, reduced a lot of the microphonics. Prior to this I could tap about anywhere on the chassis or any tubes which telegraphed thru the amp. While the squealing is somewhat minimized there is still a lot of hiss type noise when I turn up the reverb past 1 or 2. I checked the resistance on the reverb pan & it looks like it is within operating range, cleaned the RCA jacks.
Still scrounging the net for the schematic. Univox.org has nothing like this although they feature pics of this amp.
I can tell this is going to be worth the effort since it already starting to sound really rich, thick & creamy. I would love to get the reverb & tremolo working without hissing & squealing. I probably need to replace the old carbon comp resistors since they are over 50 yrs old & known noisy culprits.