One of the dect phones stopped responding to keypresses, even when pressing really hard. This is a know problem with rubber keypads, it also occurs in remote controls etc.
A keypad swapped from another phone worked fine, so it was the ‘rubber mat’ and not the board. I tried repairing the rubber mat by “painting” new conductive material1 onto the rubber pads. This made the keypad functional again for a few weeks but quickly failed as the graphite rubbed of from the pads and was left on the circuit board. Not good.
A tip online was to glue aluminium tape to the pads on the rubber key mat, but it just would not stick.
So, I threaded a thin copper2 wire through the pads. This won’t fall off. And the phone’s keypad is now functional again.
Because I have not seen this method online before, I’m posting a few pictures here. I hope this might help someone fix a similar problem.
Above picture shows how one hair of coper (from a multi stranded wire3) is threaded through one of the rubber / silicone keys.
The ends are then twisted together a few turns, cut short, and laid flat across the other direction (the direction the wire did not cross). See below picture.
Close-up of the result above.
And overview of the whole keypad after it is done. Preferably the wire goes in such direction that it crosses the meanders on the board. Also in the picture the insulation from the wire (red) and a few leftover copper strands.
Be careful not to rip the needle through the rubber pad, this happend on my first few tries. I then threaded the wire in another direction and it still worked.
Also, as a bonus here are a few pictures I took earlier of this phone4 ‘s internals:
Footnotes
- Graphite from a aquarel graphite pencil: “Karisma graphite aquarelle” “England berol Karismacolor soft”. It is quite conductive, but easily rubs off, so is not suitable for keypad repairs. ↩︎
- I worry a little about oxidation, but had no gold or silver wire at hand. Perhaps filigree wire would work? ↩︎
- Do not use enamelled or lacquered wire, as that is insulated, it won’t work. ↩︎
- It is a
Gigaset A220 ↩︎
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