Master keyboard - some keys not working

[aeberbach]

I have a new to me Master - the keyboard has a few keys that are not working. So far I am at the "this is not a language" stage because I can't spell "*configure" - the 'o' will not work!

- with the keyboard unplugged I have checked that the keyswitch is normally open but is closed when the key is pressed.
- no damage to traces on the back of the keyboard assembly can be seen.
- have verified that every connection in the keyboard cable is good from the point it is soldered to the back of the keyboard to the sockets that connect to the computer and none are shorted together

Where would you look next - is there a chip responsible for keyboard decoding that could be faulty?

[Ukwebb]

the keyboard decoder is the large chip just behind the keyboard connector but i'd doubt its that
that also makes use of the 6522 just infront of the keyboard connector. ( i have had one of those die)

My bet is that there is another keyswitch giving interferring signals.
try testing every other key first before you get into chip swapping.

or another master keyboard if you have one, or can loan one

[aeberbach]

Thanks! I will check every switch and see that no row/column line connects to another, then try swapping in a 65C22N. Nice that they are still made!