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Subject: Re: [chromapolaris] Polaris stubborn tuning problems

From: Bob Grieb <bobgrieb@...>
Date: 2015-07-10

Until Paul jumps in, I guess anyone can throw out ideas,
so I will...

The output of each synth channel goes through a 4053 MUX to create
main out and alt out.   Did you replace those on the two offending
voices?   Also, did you scope the signal coming out of the 
"tune buffer"   and also the signal at the output of the 1489 Z46?
I know that those are not specific to particular voices, but maybe if
they are bad, some voices could be more affected than others?

Bob


From: "klosmon klosmon@... [chromapolaris]" <chromapolaris@yahoogroups.com>
To: chromapolaris@yahoogroups.com
Sent: Thursday, July 9, 2015 5:04 PM
Subject: [chromapolaris] Polaris stubborn tuning problems

Currently working on a Polaris that was severely mistreated.
Replaced the membrane panels, several pots;  upgraded the ROMs; tuned &
scaled the power supply, DAC, CPU and voice board per the service manual.

Two voices (3 and 5) will not pass tune.  Re-enabling them shows that
Oscillator B on both voices scales sharp towards the upper part of the
keyboard;  also, when playing the filter resonance from the keyboard,
those two voices are out of tune with the rest.

What I've done so far:  swapped out ALL ICs on the two offending voices
-- no change.
Swapped out all the sample/hold caps and oscillator timing caps on the
two offending voices -- no change.
Replaced the four ICs (Z60 - 63) in the sample/hold control circuit --
no change.

At this point, I'm out of ideas as to why these two voices are behaving
this way.
All memory functions, internal and external controls, and other synth
features are working correctly on all voices.

Any suggestions?
Thanks.
~GMM


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