strange HP-97A

[BobVA]

(08-06-2016 06:50 PM)Katie Wasserman Wrote:  ...It's possible that the service manual schematic is wrong and it has the labels for segment B and segment F reversed. If so, then this is exactly the 4 bits needed to decode the decimal digit and with a bit of logic one could not only simulate the pressing of the keys but also read the number on the display all through the 14 pin connector....

Good theory! It made me look at the pictures HPC posted again. The last wire on the right (brown) is connected to a trace that *might* go to XA2P1 pin 16 (SB), which would provide the "B" segment line.

HP Collector, if you have occasion to open it up again, or a picture from a slightly different angle, could you check to see if there's a connection to pin 16?

Fun puzzle!

Bob