[sdiy] Prophet 5 scale problem

[Michael E Caloroso]

You do not mention if you probed the key CV path fanning out from the
4051 with a 'scope (DMM isn't enough).  That should tell you a lot.

MC

On 10/12/16, Adam Inglis <21pointy at tpg.com.au> wrote:
> I have a P5 here that seems to be working OK except that the lower ranges of
> the 2 VCOs for each of the 5 voices are randomly off scale/out of tune
> across the keys.
>
> It seems to correspond roughly to a key CV lower than 3 volts with the VCO
> pitch pots at their mid-range (as evidenced by the CV out jack). Above this
> both VCOs track well in tune and scale. If I pitch both VCOs to their
> highest range, the top 4 octaves of the keys are in tune, just the lowest is
> out. Doing the inverse, most of the keys are out of scale except the top
> octave.
> It does appear to be all 5 voices affected, so I’m having trouble narrowing
> it down to one chip, say e.g. a CV demuxer 4051, which are a common problem.
>
> All 14 bits of the DAC are pulsing.
>
> Further tests are obviously needed, but any clues greatly appreciated.
>
> AI
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