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--- In chromapolaris@yahoogroups.com, "Paul D. DeRocco" <pderocco@...> wrote:
>
> > From: minimelisma
> >
> > That's exactly right. Before, nearly all of the buttons on
> > the right panel worked, but you could tell that some of them
> > were worn out because of poor responsiveness. Absolutely none
> > of the buttons on the left were working before the
> > replacement, so I chalked it up to a broken connection in the
> > plastic ribbon cable. Indeed, upon removal of the panels, the
> > plastic tails did crumble, so I confidently and carefully
> > installed the new panels knowing that they would resolve my
> > issues. Unfortunately, I'm right back where I started, albeit
> > with brilliant new membranes. All of the buttons on the right
> > side work and none of the buttons on the left side work, just
> > as before. It's puzzling. I have LED illumination and control
> > via linear potentiometers on both panels, however, so I've
> > ruled out installation error. Must be component failure on
> > the PCB pertaining strictly to the buttons, I figure.
>
> I don't see anything in the circuit that only pertains to the left membrane
> switch panel, besides the connectors themselves. Make sure the ink lines on
> the membrane switch tails line up with the contacts. Sometimes the tails can
> be cut off-center a little, causing a misalignment which can be fixed by
> trimming the edge of the tail a little. Also, double-check that there are no
> remnants of the old tails clogging up the connectors. The only other thing I
> can imagine is that three of the outputs of Z1 are bad, but that's really
> unlikely, since it's a TTL part, and they're almost indestructible.
>
> If you still can't find anything, it'll take some electronic diagnosis, like
> seeing if you can measure continuity between certain J8A and J8B pins when
> certain switches are pressed (which will probably take three hands). The
> service manual lists the connector pins corresponding to each switch, on the
> last two pages.
>
> --
>
> Ciao, Paul D. DeRocco
> Paul mailto:pderocco@...
>