I have restored an old Cherry G81-3000LAD keyboard and all keys work again. Except one, the left ALT key. When I measure both PINs directly at the IC (Motorola ZC86956P keyboard controller) and press the key, the circuit is closed via the two foils. On the upper foil (left niner contact) several keys are connected to the ALT key. On the lower one the ALT key seems to be completely separate (leads to the outer left of 19 pins). Does anyone know this phenomenon? Is it likely that a single IC contact is defective?
I have tested another Cherry keyboard on the same computer with keycheck.exe and there the left ALT key lights up when you press it. With this keyboard the menus in "Edit" (DOS) can also be called. Nothing happens with the G81-3000. The right ALT-GR-key works!
Thanks!
