The operation manual dates to October '79. It's already driven by a microcontroller, a MOSTEK MK3870 with 64 bytes of scratch RAM, 64 bytes of executable RAM and up to 4k of mask ROM.
The keen eyed among you will have already spotted another problem. Two segments on the LCD are out, along with two status indicators.
The LCD is a piece of glass with contacts deposited on it in a very thin layer. A rubbery piece with conductive inlays provides contact with the PCB. Held together by a plastic contraption. I gonna need a conductive pen to fix his.
Back together it goes for now. I'll postpone the calibration until I put one of the voltage references in a nice enclosure and got its accuracy verified. For the LCD I'll get a conductive pen and try that. Shouldn't be too hard to adapt LED 7 segments either. There is no way I could find a replacement for this LCD. It's definitively custom due to the indicators.
If I can fix the LCD display, it might be worth just throwing it on ebay and putting those 100 bucks towards a 5 1/2 or 6 1/2 digit meter. I really should upgrade