Rhodes Chroma Polaris

Hi Paul (and list) -

Following up from my last report, I did go on and change all the timing circuit logic, starting with Z37, and that was indeed the ticket. Specifically, Z37 (74HC393) failed, and somehow Z46 (1489A) hadn’t completely failed, but the tune routine seemed to occur faster and the tuning more consistent with it replaced.

Yay, another Polaris is back to life!

Thanks, all.
e



> On Jan 26, 2016, at 11:11 PM, 'Paul D. DeRocco' pderocco@... [chromapolaris] <chromapolaris@yahoogroups.com> wrote:
> 
> > From: Eric Frampton
> > 
> > Yes, when forcibly enabled the channels sound completely 
> > normal otherwise.
> 
> Other question: when you forcibly enable the channels, does the first
> oscillator sound in tune? I'm wondering if it gets part way through the
> process on each channel before failing, perhaps failing on the pulse width
> or the filter. If oscillator 1 is sour, then I'd concentrate on the "Timer
> Interface Serial I/O" section. If it is in tune, then the problem may be
> elsewhere.
> 
> The auto-tune measures the period at four pitches for osc 1, then osc 2,
> then the pulse duration at two widths for osc 1, then osc 2, then the
> period of filter self-oscillation at two pitches. Sometimes you get a clue
> by where it fails.
> 
> If you need help figuring out the Timer Interface Serial I/O section, let
> me know. Or, if you have spare parts, you could try replacing the ICs in
> that section, and hope that fixes it.
> 
> -- 
> 
> Ciao, Paul D. DeRocco
> Paul  mailto:pderocco@... <mailto:pderocco@ix.netcom.com>
>