Schematics for a Randall RB750

[aortizjr]

Anyone by chance have a schematic for a Randall RB750. The PCB says RB500 so that would probably work as well.

I called Randall/US Music and they don't have one on file for it.

It is a pretty strange problem. Low output and really distorted in the power section only (bypassing the pre by using FX return, swapped tubes). Everything else, include DI, are all fine. Headphone out is distorted too but that just comes off the speaker outputs with a resistor.

So definitely something in the final power stage. Nothing obviously burned or anything. Schematics would really help.

Thanks!

[J M Fahey]

I have somewhere the old RB300 schematic, AFAIK the RB500 is quite similar, but no tubes to be found at all.
I'm referring to the "real" USA Randall.
Then some Oriental company bought the brand and the cosmetics, but makes absolutely unrelated stuff.

As of actual servicing, visuals don't help much, that's why God gave us the Multimeter.
Do you have the proper rail voltages?
DC on speaker output?
Open emitter ballast resistors?
Shorted power transistors?