Sinclair ZX80 / ZX81 / Z88 Forums

Wasn't sure where to post this but since there are a lot of smart folk here into their tinkering, I thought I'd post it here.

Just taking apart a gamepad for a Sharp X1, which has the usual arrangement of button pressing down some conductive padding which bridges two contacts on the PCB. The pad didn't feel much like metal, so for no apparent reason (since I knew it was conductive, it HAD to be conductive) I prodded it with a multimeter - noticing that the pointy ends of my probes left a little dent in the material.

Any idea what it might be? It feels almost rubbery but I can't say for certain without trying to tear them from the bigger rubber things they're embedded in.

It's just carbon paint on the rubber nodule. You can buy it on eBay, or wherever.
Normally used in most remote controls, the paint wears thin after use stopping the button working (how many remote controls have you had were you really need to press the buttons hard because they no longer conduct very well).

To repair, either paint with carbon paint, rub over with a soft pencil (works ish, but I don't know how permanent that would be) or do what I do and cut out a small piece of tin foil and use double-sided tape to stick it over the carbon area

Regards.

Grant

I'm not sure whether its conductive carbon 'paint' , I think they used a thin amount of carbon impregnated rubber as I've seen many remote control 'pads' over the years and the carbon hasn't 'come off' or worn off in any kind of way but the surface has gone 'shiny' as if the rubber is starting to perish in some way.. and if you cut through the pad you can see the 'black' area extends a little way into the rubber... but yes, you can buy conductive carbon paint, or even conductive 'glue' which is what I've got and might also be suitable for repairing/making these pads.

Thanks guys - I really appreciate the info. It might come in extremely handy for me in the future.

The joycard (weird name) works fine but I couldn't resist taking it apart. I wonder if the approach taken here is more or less reliable than the use of microswitches etc.