CPC6128 Keyboard Issues

[Jurassicc]

Hi, I turned the CPC6128 on today, first time in several months and I have an issue with the keyboard.
When I press "C" the monitor displays "4" & "C" as if I was pressing both keys one after the other. When I press F2 I get left cursor movement and "2" displayed.
Likewise if I press "4" I again get 4 & C displayed and when I press left cursor I get left cursor movement and F2 (2) being displayed.
I've taken the apart the membrane and cleaned it. I've inspected for any possible shorts between layers and cannot see anything obvious.
Is this new membrane territory or something up with the PCB.

[eto]

Sounds like a short between data bit 0 and 6 of the keyboard-matrix which goes directly to the soundchip. If there is no short while the CPC is off (still try key-presses), it could also be that it's the sound chip itself. 

[Bryce]

Clean the membrane first, it may just be pads stuck together.

Bryce.