the switch and slider both function, so I continue to suspect it's just the LED.

Thanks much for the new panels. Installation was not a problem at all, and went slightly faster than I thought it would. Looks and works great, and a nice gentle push makes all the switches work. The instructions were excellent.

The sockets that the membrane tails feed into are not as tight on mine as I suspect that they used to be, so I'm resorting to putting some gaff tape on the back of the membrane leads to thicken them up a little assuring contact in those sockets.

Otherwise things are ok. I ordered a replacement LED this morning, so I'll solder that in next week.

--- In chromapolaris@yahoogroups.com, "Paul D. DeRocco" <pderocco@...> wrote:
>
> > From: Paul Kavicky
> >
> > My Chroma Polaris II has an issue where the sweep red light
> > doesn't work. All other membrane panel switches and lights
> > function properly. It used to work and due to a long period
> > of touring away from the synth I cannot say when it stopped working.
> >
> > I have just completed the membrane panel update and that has
> > went well. It didn't cure the issue with the sweep light not
> > coming on. Perhaps someone could point me towards which
> > things in the polaris I should be looking at specifically or
> > is having a light go out a likely possibility? if there is
> > some particular connector I should be looking at, or wire, or
> > whatnot. I'd just like to be pointed in the right direction
> > so that I could possibly troubleshoot this some more while
> > the synth is still apart.
>
> Are you saying that the function works, but the LED stays off? It's most
> likely just a bad LED, although you can check this with a multimeter by
> measuring the voltage across it when it is supposed to be on. If the LED is
> open, the voltage will be a typical TTL logic 1 output voltage of at least
> 3.5V. If the shift register is bad, it will be less than the on voltage of
> the LED, which is about 1.5V. I believe the LEDs we used predated the
> high-efficiency LEDs that are available now, so try to find a crappy old
> low-efficiency one, or the replacement will look a lot brighter.
>
> There was also an issue with the shift registers that drive the LEDs
> sometimes being mis-clocked by ground noise, which was solved in many
> production units by soldering a capacitor around 0.1uF between the digital
> ground on Z6 pin 7 and the nearby LED ground bus. If that mod has already
> been done, it will be clearly visible on the circuit side of the board way
> over on the left end of the panel. If it has not been done, tacking a
> capacitor in there may help.
>
> If the function doesn't work either, recheck the alignment between the tails
> on that side of the panel and the connector. But it's hard to imagine
> misalignment only affecting one switch, instead of a whole matrix row or
> column.
>
> Any feedback on the membrane replacement process? Were the directions clear?
> Anything I should change?
>
> --
>
> Ciao, Paul D. DeRocco
> Paul mailto:pderocco@...
>