Rhodes Chroma Polaris

> From: charlespjackson
>
> Recently I began to experience an issue with my Polaris going out
> of tune.  Upon doing some research and reviewing older posts here
> regarding similar problems it appears that the culprit has been
> narrowed down to a faulty Channel (1).  If I manually disable
> this channel then the Polaris functions and stays in tune just fine.
> From what I've gathered so far it seems the problem might be some
> bleeding and/or bad (Sample & Hold) caps?
> I would just like to know if I'm accurately diagnosing the
> problem and if so how intricate/expensive a fix this may be?  Are
> the parts necessary for such a fix available?  Where might I be
> able to locate them?

I think it's usually the 4051 analog switches that leak. They're pretty easy
to find, since they're near the left end of each channel, which are the six
step-and-repeat sections on the right half of the board.

This is a pretty easy thing to diagnose and fix, for anyone with a scope and
good soldering skills. You can tell if a S&H is leaking by looking at the
op-amp outputs (pins 1, 7, 8 and 14 of the nearby TL084/LF347 parts) and
seeing if there's any sawtooth modulation larger than a few millivolts.

--

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