Rhodes Chroma Polaris

> From: minimelisma
>
> In my original diagnosis, the membrane buttons on the left
> panel of my Chroma Polaris were non-responsive to touch, so I
> ordered and carefully installed Paul's replacement panels
> according to the instructions at rhodeschroma.com. This
> needed to be done, no question about it, but the left panel
> buttons still do not work. Disappointing! I suspect the PCB
> that controls this half may have a failed component, but
> due.to the scarcity of replacement boards, I will have to
> isolate and repair this issue. The mod/pitch levers are also
> not functioning, but that may be beside the point right now. Not sure?
>
> Before I go through the whole board probing for voltages with
> a multimeter, does anybody know more about this issue? Maybe
> which components could be the likely culprit?

--- In chromapolaris@yahoogroups.com, "Paul D. DeRocco" <pderocco@...> wrote:
>
> > From: minimelisma
> >
> > In my original diagnosis, the membrane buttons on the left
> > panel of my Chroma Polaris were non-responsive to touch, so I
> > ordered and carefully installed Paul's replacement panels
> > according to the instructions at rhodeschroma.com. This
> > needed to be done, no question about it, but the left panel
> > buttons still do not work. Disappointing! I suspect the PCB
> > that controls this half may have a failed component, but
> > due.to the scarcity of replacement boards, I will have to
> > isolate and repair this issue. The mod/pitch levers are also
> > not functioning, but that may be beside the point right now. Not sure?
> >
> > Before I go through the whole board probing for voltages with
> > a multimeter, does anybody know more about this issue? Maybe
> > which components could be the likely culprit?
>
> Do none of the left panel switches work? Do all of the right panel switches
> work? If this isn't the case, it would be helpful to have an EXACT list of
> which switches don't work.
>
> --
>
> Ciao, Paul D. DeRocco
> Paul mailto:pderocco@...
>

> 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.

--- 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@...
>

> From: minimelisma
>
> 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 Syntaur.com 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.

 

> From: minimelisma
>
> 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.

In one way I'm glad I was right about there being some junk in the
connector, but in another way I'm not, because it means I've got to
explain to future customers that the job of replacing the panels might be
a little more difficult in some cases. In the spare Polaris that I just
set up for testing membrane panels, I had one connector that had a
fragment of the old tail in it that I simply couldn't get out, and I had
to replace the connector, which is an easy soldering job for me, but not
for everyone.

> 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 Syntaur.com 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.

I seem to recall that originally we used some larger sliders, more like
the Chroma's, which had brass-colored metal casings and shafts. If you
could measure the spacing of the mounting holes on the PC board, I could
look through my old junk and see if I have anything that would line up
with those holes.

As to the levers not responding, the first thing to do, if you haven't
already done it, is to do the lever cal, as shown on page 6-2 of the
service manual. If that doesn't fix it, then measure the voltage on the
wiper of each pot, and make sure that it is in the neighborhood of 2.5V at
rest. If everything's at zero volts, then you've got a connector problem
somewhere. If it's nonzero, but nowhere near 2.5V, then you may have a
mechanical misadjustment, which you fix by loosening the nut and turning
the body of the pot until you get around 2.5V in the center position.
You'll have to pop out the springs to do this.

> 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.

Might as well put in new ones. The old ones may be approaching the point
where the RAM might start dropping bits, even if it's not showing any
corrosion.

--

Ciao, Paul D. DeRocco
Paul mailto:pderocco@...