HP-97 keyboard problem

[Paul Berger (Canada)]

No if it is column that is out it's not a bad cathode driver, they drive the rows, the columns are driven by the PIK chip and if it is truly bad the only place to get another is from another topcat, the same applies for the cathode driver it is also a custom chip but in the case of a failed cathode driver there are alternatives to get them to work, but would involve modification. I have not verified this however my guess is that when a key is pressed, it pulls down the column line under it when the cathode driver for the row is active.

For your missing column check carefully between the KBA pin on the PIK (looks like pin 24) and the first key contact you will need to trace from the P1 connector to the pad on the keyboard the actual wiring likely does not look like a nice grid. Check right from the actual pin on the chip as it could be a cold solder joint. If the connections are good I am afraid it is likely a PIK chip. Do all of the voltages inside look good? Its a long shot but if one is marginal they can do some weird things.