I took a chance and bought a Tabor 6020 parts unit with an "unknown problem".
Before powering it up, I replaced all electrolytics because one was bulging.
With power on, voltages checked good, and it booted as it should (almost, read on...)
However, with a signal applied at the input(s), error flashes, "No Ref".
It has the factory installed TCXO board.
TCXO tests good at 10Mhz.
At the ref-board to main-board junction, pin 6 should read 100Mhz.
I'm getting a sine about 115Mhz @ 150mV P-to-P.
For some reason the ref-board is not being recognized by the rest of the system.
During boot, it only says "6020" , and it should read "6020-1".