Keyboard Issue

[Jpl2]

Bought a Ts1000, received DOA. Updated ULA, Power Regulator,,,,got it to gray screen. Updated Z80A, happiness K Prompt. Tested existing keyboard. Dead. Replaced with new one. 1st and last 2 columns dead. Tried another Keyboard, now only 1st and last dead. Searched thru the forum, found issues with dead rows but not dead columns….any advice appreciated? Keyboard in now is brand new membrane, both leads look solid. Thank you in advance.

[desiv]

One thing that could be happening is that if the original keyboard connection was really brittle, it might have left some pieces of itself behind in the connector.
If you can, try to make sure it is as cleaned out as possible. (They do also sell replacements for those, if the connectors themselves need to be replaced)
Also, you can test them with a multimeter on the pins for the connector and a diagram:
https://postlmg.cc/BjPdw4wr

(Not always physically easy to hold the probes and hit the key at the same time.)
But that will let you know if the press is making it from the keyboard to the solder connection points for the connector.

I know I pulled mine out recently, and the first time I put it back together, there were some keys not working. Had to unplug it and plug it all back in again.

Good luck...

[1024MAK]

You can also use a thin solid copper wire (e.g. an off-cut from a fixed telephone or Ethernet cable) with the insulation stripped back by say 6mm at each end to simulate a keyboard key and see if the ZX81/TS1000 responds. Touch one end in a contact in KB1 and the other end to a contact in KB2. Repeat for each combination (there’s only 40 ).

@desiv - ahh, you found my diagram from WoSf (link).

Mark

[Jpl2]

Thank you both for the suggestions, I didn’t think about that there may be a chunk of old membrane caught in there. I have some replacement keyboard connectors coming in for another bad board that the connector was cracked so that will be my last shot if above doesn’t work.