Rhodes Chroma Polaris

--- In chromapolaris@yahoogroups.com, "Paul D. DeRocco" <pderocco@...> wrote:
>
> > From: wasteking1
> >
> > i finally did the memory upgrade on my polaris--- it was very
> > easy. but upon doing all sorts of tests to prove its ok i noticed
> >  that the touch sensitivity was out on  voice #1  -- It played
> > fine but every sixth note would NOT play with a soft touch...
> > just a harder one. I did the voice isolation test and indeed
> > voice 1 would not play softly.  would this be an issue with a
> > chip  or connection in Voice #1?  or  in the keyboard? I had
> > cleaned all the contacts, all notes do play.
> 
> My guess would be something around the volume sample-and-hold circuit,
> causing its output to have a negative bias on it. You could test this by
> selecting a steady (non-decaying) sound, and turning the volume parameter
> down, and note if that particular voice disappears before the slider gets to
> the bottom. I've seen excessive leakage in the 4051 switches (Zx01 or Zx02),
> as well as failures in the capacitors (Cx35). Could even be the FET buffer
> (Zx03) or the Curtis chip (Zx09), but that's less likely. You could check
> the volume control voltage (Zx03B output) with a voltmeter, although a scope
> might reveal a negative-going sawtooth wave at the sample-and-hold update
> rate, if there's leakage.
> 
> --
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@...


>I tried your suggested volume test with a long sustained sound and the volume slider --it seemed to attenuate in a normal way-- no early cut out. and i repeat, the non-touch sensitive playing  is fine
 I was wondering if each of the 6 voices had a seperate chip(?) that dealt with interpereting the volume of the touch sensitivity signal  that wouldnt affect the normal full signal. [would that be the Zx09?]  is this touch /volume  located in the sample/hold  area? I have the schematics, but that doesnt really descrbe the function of the  various parts. [ I also have a dead polaris to scavenge chips from  if that would be helpful ] sorry, but i have no scope, just a meter.