On 24/10/2019 15:00, Brian Gaff wrote:
What type is it. Type one two sheets of flexible pcb with a rubber or hard
button on top. Normally can be fixed by silver loaded paint if you can get
the layers apart without doing more damage.
2 blister ones where the top of the blister is conductive inside and shorts
connections underneath. Very hard to fix successfully since you can't get in
to them
3 The remote control type, bumpy pcb underneath, where the contact points
are higher and the bottom of the button coated in a conductive material.
These tend to dry out and turn to powder and this fills the gaps and either
shorts some keys out or stops what is left of the conductive button from
making a contact. In this case, disassemble Clean the pcb using an
ultrasonic cleaner bath to get the gunge out, and then see if you can get it
to work. In the end though the conductive material goes and you end up
having to glue ally foil to the buttons, which is both fiddly and can
eventually fall off.
I feel sure these makers could come up with a better solution than any of
these myself, even if its just a bit of springy phosphor bronze below the
keys, but I guess these other things are almost off the shelf solutions for
simple keypad designs.

I'm sure others will have their pet methods, but in the end a new assembly
might be better for something so crucial as an alarm where key repeats might
lock you out.
Brian

I've assumed, from the feel, that it's the sort where a conductive area
on the bottom of the button bridges tracks on a PCB. I won't be able to
dismantle it for a few weeks but until then I might try changing the
codes to avoid the worn-out digits.