WARNING: Tube/Valve amplifiers use potentially LETHAL HIGH VOLTAGES.
Building, troubleshooting and testing of these amplifiers should only be
performed by someone who is thoroughly familiar with
the safety precautions around high voltages.
I looked and could not find the schematic, at one time they used to post them to their site which has changed a lot since the last time I looked and is really hard to look at. (all those flashing things )
Email them directly, the owner's manuals of older products all had the schematics in them. (I bought a few, and I also had them oem products for me back at the turn of the century. ) They might be willing to provide one for your personal use.