Keyboard repair help

[pandy71]

Originally Posted by Screechstar

As a reference, when I measure resistance I get about 150ohm across the carbon pads that work for me. Even after a paper-rub, that one I removed is up at around 700ohms, so may need a more intrusive fix is needed for that, like conductive paint, pencil rub or something.

Paper rub probably not help to much, if thorough IPA cleaning not helping this then perhaps you can find some cheap PC keyboard as conductive rubber part donators. PC keyboards should share same design with Amiga.

This video may be helpful too [ Show youtube player ]

[Jope]

I've revived a totally dead C128 keyboard with only a blank piece of A4 paper and some compressed air. Done several other intermittent Mitsumi boards too, but the one with absolutely zero keys registering before the treatment was an amazing transformation.

I always use it first before making a mess with graphite or remote control paint.

[Matt_H]

Update:
The numpad "2" key is now working. Rubbing the carbon pads on the membrane and the key plungers did nothing, but I slathered the membrane pads (and patched the possible membrane circuit break that Snoopy1234 identified) with CaliKote.

Slathering the pads for the "-" key did not fix it, but I didn't do a very good job of it. Gave it another/more complete coat and identified a possible membrane break on that circuit and patched it as well. We'll see what happens when it dries...

[Matt_H]

Update 2:
My “repair” on the numpad “-“ key ended up causing additional damage and now that whole row is dead. This is beyond my ability to fix so I’ve ordered a new membrane. It’ll take more than a month to arrive from Europe. Thank goodness they’re available, though.

In hindsight (and for anyone else fixing a membrane in the future), there was probably nothing wrong with the carbon pads. I think it was simply two separate breaks in the membrane circuit. I believe I fixed both of them, but my sloppy work on slathering the carbon pads for the “-“ key ended up bridging/breaking other connections. Ugh.

I almost had this. Kicking myself for not leaving well enough alone. If I hadn’t done the carbon pads everything would probably be working now.

[Signman]

Been there my friend.