Just bought this for $35. The keyboard had some sticky keys when I tested it, but thought that they just needed cleaning. Te keyboard is now completely unresponsive. I get the correct start up screen about Basic, memory and lovely blinking cursor. I have taken the keyboard apart, cleaned - still nothing. I have tried shorting the pins on the motherboard that keyboard cable plugs into - nothing.

Any advice?

Thanks,

Martin

Sounds like the VIA or PIA chip (I forget which kind it is) that the keyboard port plugs into is shot.

Have you confirmed that pressing keys on the keyboard is detectable at the keyboard cable?

How do I detect that?

See the schematics here:

http://www.commodore.ca/manuals/pet_sch ... _80col.gif

The keyboard port is driven on pins 1 through 10, and any key press events are returned via pins A-J. What you'll want to do is use a continuity checker between each combination of pins (or a representative sample thereof) to see if pressing keys on the keyboard produces a short (which it should -- it's just a matrix of normally-open switches).

Looking at the schematic, there is the possibility that the 74LS145 (U11) chip might have gone bad too. If so, the PIA might be fine, but the keyboard never produces events because it never sees one of its input pins asserted low.