Sinclair ZX80 / ZX81 / Z88 Forums

Hi Guys,

Desperate to have the ZX81 keyboard to be fully functional. The strip connector was in a very bad shape at the time I picked this unit up and though this was the issue so I bought a fresh new keyboard from SellMyRetro but after installing, cleaning the strip connectors and put some fresh solder onto the original solder joints I still have some keys not working (ie key3, keyG...). Is this a bad ULA symptom or is any test or fix I can try out?

Thanks,
Rick

Can you please list all the keys that don’t work.

Mark

Here it is Mark,

Keys 3,8,E,I,D,K,X,M. Any Shifted function on those keys will not work also.
3,E,D and X are more or less aligned on the keyboard and same for 8,I,K and M.

Repetto74,

Try cleaning a 5 pins strip connector with some very fine emery sandpaper. If not working then buy a new set of connectors.

DesSony

Hi Dessony,

The strip connector is not the problem I think because I cleaned it with contact spray already.

Does your computer show its white "K" and its black square on the white screen? Can you touch an end of a wire on a middle pin of the 5 pins connector and another end of the wire on one pin of your own choice of the 8 pins connector and check the result on the screen?

Maybe you have to evaporate some flux off the 5 pins connector and leave some shiny solder and wash some flux with contact spray or some rubbing alcohol.

DesSony

Yes I do see the 'K' prompt and all keys are working except the one listed on my reply above. Did not try to short the 2 connectors still but will test this as soon as possible. I have also refluxed the solder joint on the back for both connectors.

It is possible that the membrane has a fault - but the first thing to check is to short the 5 way connector with the 8 way using a piece of wire.

Also check that are no pieces of the old membrane inside either connector (sometimes a tiny sliver is left behind). The pins on the connectors can also become damaged or corroded so there can be several reasons.

Hi Rwap,

Bad luck if this new keypad has a defective strip. The reason why I replaced the keypad was the original strip in a very bad shape and broken in some areas resulting in keys not working. Cannot remember if the non working ones are the same as now. I will test both connector with a wire and see the result.