Restoring a VT50 (VT52 actually) .

Mattis Lind mattislind at
Sat Dec 23 02:08:35 CST 2017

I have started to work on a getting VT50 terminal back to life. When
digging into it I recognze quite immediately that someone had done a brain
transplant on it. It has VT52 boards in it!

Was this a usual procedure?

The VT50 to VT52 shift looks like a failure of DEC at the time. So close in
time. But different board sets inside. They could have designed a board
with RAM upgrade possibility and just a new microprogram? Looks strange to
me. When the VT52 got on the market I guess it was hard to sell any VT50s
or was there a substantial price difference?

Anyhow, the VT52 boards are dead. They generate the proper sync signals but
there are no keyclick generated when pressing keys on the keyboard. Which
is quite normal since the sync is generated by a chain of counters while
the keyboard is controlled by the microprogram. The terminal uses 4 pieces
of 256 by 4 bipolar PROMs for a total of 512 bytes of microprogram.

Has anyone dumped the contents of these so I could verify them?

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