> From: karmakater
>
> this Polaris is mine, i already changed the panels & this works fine.
> and yea, i can turn on the TUNE LED and get plus-or-minus, so
> i think the slider is fine.
> The volume is always on maximum, i change it now through the
> assignable volume control,
> this works. The master volume didn't work even before i
> changed the panels, i hoped that
> this panel change might fix it.
>
> If the problem is the transistor Q1, is it "easy" to change?
> I got a little experience in soldering.

Yes, it's pretty easy. If you can't find a 2SA1029, any small PNP transistor
should work, like a 2N3906, as long as you figure out which leads are which.
However, since answering you, I realize there are other failures that could
cause the same problem, but they should be easy to check.

First, open the unit up and unplug the three-wire cable that runs from the
output board and plugs into the main board, which has an 8-position
connector at the end. If the volume remains high, then the problem is on the
output board, probably the transistor. If the volume drops to zero, then
there is a problem in the sample-and-hold circuit that drives the master
voltage control line.

This line comes from Z603-8, one of the op-amps in the fifth channel. (The
service manual is available at rhodeschroma.com.) You'd have to remove the
keyboard to get at this, but that's only a few screws. Fortunately, these
parts are socketed, so you could tell if the op-amp is bad by swapping the
part with the analogous part in a different channel, say, Z503. If that
fixes it, you're all done, because that op-amp section isn't used for
anything in the other channels. If not, then it's probably one of the CMOS
switches in the sample-and-hold circuit, which would be either Z601 or Z602.
Again, you could swap those with, say, Z501 and Z502, and if everything
works, you're done. This would mean that only that op-amp in Z603, or that
particular switch channel in Z601 or Z602, had burned out.

Ideally, you would diagnose these things by reading voltages with a meter
while moving the master volume slider. If the above doesn't fix it, then
you'd have to delve deeper and do a real diagnosis. Not every electronic
failure can be solved by swapping a few socketed parts. But you might get
lucky.

--

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