[Coco] Weird CoCo 2 keyboard problem -- any ideas?

[Arthur Flexser]

My recollection from having once opened up a CoCo 1 keyboard is that there
are no diodes, just contacts that get made when a key is pressed.

If pressing the shift key was opening a broken trace, I'd expect it to
matter which of the two shift keys you used, and you said it made no
difference.

So, I wouldn't entirely take the ribbon cable out of the running just yet,
though I'm still puzzled as to why the problem with the shift key should
affect just one keyboard column.

Maybe try simulating a keypress by momentarily shorting a row and a column
line in the ribbon cable and see if you get the expected output in all
cases, and in particular whether you can type a question mark while
simulating the shift key being down.  (Admittedly, it seems like this
requires 3 hands.)

Art

On Mon, Apr 1, 2013 at 11:23 AM, John W. Linville <linville at tuxdriver.com>wrote:

> It seems unlikely to me that the cable is the problem, since the
> unshifted keys on that column work fine, and the shifted keys on all
> the other keyboard columns work fine.  The problem would seem to be
> in the keyboard matrix itself, perhaps either a shorted diode or a
> broken trace being opened when the shift key is depressed.
>
> Anyway, with the whole keyboard column effected the problem seems a lot
> less mysterious than originally thought.  Thanks for all the advice.
>
> John
>
> On Sat, Mar 30, 2013 at 02:16:29PM -0400, Arthur Flexser wrote:
> > Before fiddling with all the tiny screws, make sure the problem isn't
> with
> > the ribbon cable!
> >
> > Art
> >
> > On Sat, Mar 30, 2013 at 12:44 PM, John W. Linville
> > <linville at tuxdriver.com>wrote:
> >
> > > On Sat, Mar 30, 2013 at 12:01:46PM -0400, John W. Linville wrote:
> > >
> > > > Swapping-out the keyboard assembly seems like a logical next step...
> > >
> > > The problem follows the keyboard.  I'm not looking forward to all
> > > the tiny screws, but at least it isn't secured w/ melted plastic like
> > > some other CoCo keyboards...
> > >
> > > --
> > > John W. Linville                Someday the world will need a hero,
> and you
> > > linville at tuxdriver.com                  might be all we have.  Be
> ready.
> > >
> > > --
> > > Coco mailing list
> > > Coco at maltedmedia.com
> > > http://five.pairlist.net/mailman/listinfo/coco
> > >
> >
> > --
> > Coco mailing list
> > Coco at maltedmedia.com
> > http://five.pairlist.net/mailman/listinfo/coco
> >
>
> --
> John W. Linville                Someday the world will need a hero, and you
> linville at tuxdriver.com                  might be all we have.  Be ready.
>
> --
> Coco mailing list
> Coco at maltedmedia.com
> http://five.pairlist.net/mailman/listinfo/coco
>