HP27: lowest keyboard horizontal row not working

[teenix]

(05-28-2019 11:32 AM)isanchez Wrote:  Hi everybody,


I swapped the HP27 keyboard in with the HP25 calculator and still the lowest line of keys did not work at all, so it seems clear it is a problem with the keyboard.

Do you have any idea what could be this malfunction caused by? The continuity is checked in al (vertical)l lines, but the horizontal line sounds weird for me.


Thanks in advance,

Kind regards

Ignacio

It sounds like the keyboard [row 7] is faulty. The pin for this row is on the lower keyboard connector, not sure if it is last on left side, or right side.

With the keyboard removed, you should be able to put an ohm meter on this pin and any column pin and see a short when the corresponding column key is pressed.

If this works, then it is possible that multiple repairs/cleanings have caused a problem with the connector on the bottom of the board or the matching CPU board connector.

If testing fails, closer examination of the key circuit board may be required.

cheers

Tony