Rhodes Chroma Polaris

Thank you for the detailed and fast response. Probably a bit over my head, but perhaps I'll get there someday...
Jesse

--- In chromapolaris@yahoogroups.com, "Paul D. DeRocco" <pderocco@...> wrote:
>
> > From: jesseterry
> > 
> > Hi, New Chroma Polaris user, and I've got a problem, 
> > wondering if any of you have an idea. 
> > 
> > I get random Pitch bend drift, like the following:
> > 
> > 11:53:37.336	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-1408
> > 11:53:37.359	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-1152
> > 11:53:37.696	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-896
> > 11:53:37.718	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-768
> > 11:53:37.730	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-640
> > 11:53:38.099	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-512
> > 11:53:38.258	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-896
> > 11:53:38.437	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-1024
> > 11:53:38.449	From MIDISPORT 2x2 Port B	Pitch Wheel	
> > 1	-1152
> > 
> > I've replaced the pitch bend and modulation pots, with no 
> > luck, and tried a different MIDI interface. I've recalibrated 
> > the pitch and mod levers with no luck.
> > 
> > It seems to go away for a bit if I reset the Polaris, but 
> > eventually starts drifting again in spurts if I use the pitch 
> > level. I can workaround by setting the Pitch Bend Lever range 
> > to zero, but then I miss out on the pedal steel pitch bend fun.
> > 
> > Any ideas?
> 
> You'll have to trace through the circuit with a meter, always measuring
> relative to the same ground, preferably near the A/D converter on the
> main board. The levers get their power from analog +12V on the panel
> board, so see if that moves concurrently with your pitch wheel MIDI
> output changing. The signals then go down to the main board, where
> they're converted to digital using a reference derived from analog +5V,
> so see if that moves. The reference is divided down from +5V with a
> trimpot (R45), so see if the output of that is stable. It could also be
> bad op-amps along the way, bad 4051 multiplexers, or even a bad A/D
> converter (Z53).
> 
> -- 
> 
> Ciao,               Paul D. DeRocco
> Paul                mailto:pderocco@...
>