Warning: This part worked for me, but there may be variations in DEC VT100 terminals or terminals based on the VT100 (like the VT105, which I have). I've attempted to accomodate what differences I may have encountered in research but definitely consult your model's documentation to ensure its compatibility before building one blindly and frying your terminal.
Like others with DEC VT10X terminals, the power supply board in mine wasn't working. I've started off with bbenchoff's here, but had to modify it to make it work with my VT105, which is essentially a stock VT100 with Advanced Video and Waveform Graphics boards.
This version corrects the 12V/GND pin placement on the edge connector (12V GND 12V GND, rather than 12V GND GND GND), and uses an isolated DC-DC converter to generate -23 (well, -24) volts. The VT100 Basic Video board uses the potential between +12V and the -23V to generate the -35V supply for the ER1400 NVRAM. This is mostly possible because of the extremely low (10mA) current maximum of the original -23V line, and the +/- 8% tolerance of the -35V requirement for said IC.
I've also corrected the edge trace pitch, as bbenchoff's, while still functional, is slightly off and some of the pins are close to the edge of the traces.