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One voice (5) will not tune

One voice (5) will not tune

2017-04-09 by listmicrocode@...

Hello,


My tech is having a challenge to fix my tuning. I have isolated the issue to voice 5 by referring to the service manual and disabling the voices one by one to find the culprit. Now that I know it's 5 all the time, I am at a loss what to do next. The voice always tunes too high, each tuning cycle (for the voice) a little different. Most times it's around really high, around 10~15 ct to high on my tuner, and if I get very luck, around 7 ct too high, but still way off from the other voices. My tech has done the below, work, but has not resolved the voice 5 high tuning issue. Is there anything I can do on my own, or any area I can point him to that would assist?


It's strange that he notes Voice3, while I see it as Voice5. Maybe it's simply he saw that Voice3 was the worse at the time?????


Work already done:


Change Voice3 S/H IC chip. (TL082)

Change OSC CV resistors x 6 (0.1% selected) (100Ω0.1%)

Adjust +5.0000V reference voltage.

Adjust D/A offset to 0.0000V



thanks,

RDP


RE: [chromapolaris] One voice (5) will not tune

2017-04-09 by Paul D. DeRocco

> From: listmicrocode@...
>
> My tech is having a challenge to fix my tuning. I have
> isolated the issue to voice 5 by referring to the service
> manual and disabling the voices one by one to find the
> culprit. Now that I know it's 5 all the time, I am at a loss
> what to do next. The voice always tunes too high, each tuning
> cycle (for the voice) a little different. Most times it's
> around really high, around 10~15 ct to high on my tuner, and
> if I get very luck, around 7 ct too high, but still way off
> from the other voices. My tech has done the below, work, but
> has not resolved the voice 5 high tuning issue. Is there
> anything I can do on my own, or any area I can point him to
> that would assist?

If your Polaris has socketed chips, which I think they all do, then you can swap one chip at a time between that voice and another. If the problem follows one particular chip, then replace that chip. Otherwise, there's a problem on the board. A leaky S&H capacitor is a possibility. The most likely bad chip is probably one of the 4051s in the S&H circuit. It might be worth changing Z62, too, since that factors into the tuning for all the voices.

--

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