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Subject: Re: Left membrane panel woes

From: "minimelisma" <coburn@...>
Date: 2013-08-15

Thanks, Paul. I finally found some free time and was able to resolve the panel issue. I'm happy to report that the problem was just a remnant of the old tail clogging the connector, as you said. Didn't need to break out the multimeter for that! I knew it wasn't your panels, but some stupid mistake on my part that was to blame.

On the other hand, I'm still having trouble resolving two other unrelated issues: The mod/pitch levers still aren't responding and the linear potentiometer sent me (the same as pictured on their site) to replace the "assignable control" slider doesn't seem to match the old component. It's not as wide, and the pinout doesn't match up. Strange. The only thing I can think to do is rebuild the old one using the internals from the new one. I'll let you guys know if that works out, but I'm still clueless about the mod/pitch issue. Seems like they should be functioning, as they even still have their... springiness about them.

Also, my unit still has what I believe are the original D-cell batteries? Matsushita brand? Remarkably, they're still working, and show no signs of corrosion, but I just know that they should be replaced at this point.


--- In, "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@...