[Coco] CoCo 64K (26-3126) Keyboard Issues Follow-up

[Arthur Flexser]

It does sound like a spill is the most likely explanation, given the
further information you describe.  With the keyboard unplugged, you could
try to verify with a meter that some lines are shorted to others, which
would at least definitely pin the problem down to the keyboard itself.

At least some models of keyboard are held together with a whole bunch of
tiny screws that must be removed.  Tedious but straightforward.

Art

On Sun, Dec 10, 2017 at 12:58 PM, Christopher <piperfox74 at gmail.com> wrote:

> Folks,
>
> Thanks for the replies.
>
> A quick follow-up:
>
> 1) No joysticks are plugged in.
> 2) I disconnected the keyboard ribbon cable, checked continuity across each
> conductor, seems fine. Unplugged and replugged in the keyboard several
> times in case there's oxidation. No effect.
> 3) It doesn't look like the keyboard's ever seen a spill. It's immaculate.
> Admittedly, I haven't taken it apart. I'd consider doing that if I had some
> instructions.
> 4) The PIA in this unit is a 6822. I had a spare 6821 and swapped it in.
> Saw a similar issue. (I've read the 6821 isn't necessarily a direct swap
> for the 6822?)
> 5) For the most part, the issues seem to occur across keys mapped to pins
> 9, 10 and 11 on the matrix, e.g. pressing 1 or 2 gives "12" on screen,
> pressing Break clears the screen and inserts a line feed, etc. I'd say the
> issues definitely seem localized to keys mapped across pins 6 through 11.
>
> I don't have another PIA to test with, so it looks like I may be out of
> luck on this unit. If it turns out this is not a quick fix or is otherwise
> out of my skillset or available parts, I'd be willing to part with it for
> the cost of shipping if anyone is interested.
>
> Thanks,
>
> Christopher
>
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