> From: gopalsulleniii
>
> I have a chroma Polaris in pretty good condition. I just
> replaced the front panels with new ones that I purchased from
> Paul. Now I am able to use the lower function button and
> several of the other buttons that did not work at all before.
> I still have one problem, however. The upper function button
> does not appear to be working correctly and I am needing some
> help troubleshooting the cause.
>
> I do not seem to be able to get the unit to go into the
> diagnostics mode. I can press the upper function button and
> it will not stay lit. If I tap it repeatedly very quickly
> occasionally I can get it to light and stay lit. However,
> when I try to initiate the diagnostic mode the keyboard will
> freeze up.
>
> I have tested some of the lower function buttons and
> combinations and and able to get the adjustments mode to work
> where I can modify voices. That is really satisfying.

So when you hold your finger on UPPER FUNCTION, does its LED light up until
your take your finger off? Or does it flash? Or does it do nothing usually?
Do all the other switches work normally? Does the instrument auto-tune
successfully, and sound normal?

Since you just did the membrane switch replacement, that's where I'd start
to look. Sometimes, the silver ink traces on the tails are a little off
center, and they don't line up very well with the contacts in the
connectors. It might be a good idea to carefully pull them out of the
connectors and plug them in again, rechecking the alignment. Since your
problem is with a right panel switch, and its connectors are on the long
edge of the board, you shouldn't have to remove the left panel board.

Also, connectors are the #1 source of problems, so unplugging and reseating
other connectors, like the big ribbon to the panel, and the power supply
connectors, is worth doing.

There could be more than one problem, too. When you say that pressing UPPER
FUNCTION doesn't work but tapping it sometimes does, that makes me think
that some noise is interfering with one or more switch lines, perhaps an
unstable power supply voltage. And when you say the keyboard freezes when
you go into diagnostic mode, that makes me think the EPROMs might be
dropping bits, which can only be fixed by reprogramming them.

--

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