I made a few inquiries back in the day and never found anyone who was able to discover any circuit diagrams for tommy's gear.
Here is a thread that speaks more to the issue and what others found:
https://www.audiocircle.com/index.php?topic=180720.0
Here is a repair place suggested by Leo at Orchard Audio who knew Tommy and worked with him briefly:
https://www.circuitrework.com/