Archive of the former Yahoo!Groups mailing list: Discussion about the Korg PolySix synthesizer

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Subject: Re: [PolySix] RE: Lots of pots not working

From: Bob Grieb <bobgrieb@yahoo.com>
Date: 2014-01-09

Josh,

     I would use an ohmmeter to check the resistance from IC1 4051 front panel mux
pins 9,10 and 11 and also INH1 and INH2 all the way back to the same signals on
the CPU chip and on IC23 on the 367 board.   With power off of course.   That way if you have a problem anywhere along the way you will see it.   I think you said you changed that 4051 already. If not, I would change it now.   It seems you are getting a mixture of pots, which could either be a bad 4051, or simply a mux select line that is high-resistance or possibly floating.

    Bob


From: "josh.nursing@gmail.com" <josh.nursing@gmail.com>
To: PolySix@yahoogroups.com
Sent: Thursday, January 9, 2014 3:19 PM
Subject: Re: [PolySix] RE: Lots of pots not working, MG, VCF, EG.

 
Interesting results, Bob: at the DAC calibration step, only Effects Speed makes Leds 1 light up to 4 (in the very first values near Min), all the while LED 5 staying put, and this only when Cutoff is at 0. If I put Cutoff at Max, then the LEDs stay at 1 & 5 On.

I reckoned from the Service Manual that VR 7 makes the two LEDs 'open sideways' until they reach 1 & 8, so I used FX Speed to set the LEDs 4 & 5 ON, and the turned VR7 (which I had reflowed and continuity-tested recently), and it does work.

So, both VR7 and VR6 do work, it's just there's an issue at or near the line which deals with LED 5 onwards.

Any thoughts?

Yash