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?
