Got these as a couple of basket cases a few years ago.
Got them running & Pwr supplies are at right.
Made new Hi-Z input speech amp/Modulator.
Pre-Amp is copy of Harvey Wells TBS-50 circuit.
A squint view of the bottom of the speech amp chassis.
Used Ckt from Harvey Wells TBS-50.
This is how it looked when I started, it was a real mess. It looked like they just stopped mid stream and closed it up.
One day, long long ago, someone swapped out the 1625s and replaced them, and all the tube sockets, with 807s. Why would one do that???