Six Trak parameter edit fix


I have a Sequential Circuits Six Trak that no longer allows me to change parameter values. The Value LED does not illuminate, and the value knob does not change the value. The pitch, mod, and other knobs are non responsive as well. The voices play fine, and all of the other buttons appear to work. Has anyone eperienced this on a six trak?

thank you,

There are multiple possible causes for the value issue, the simplest is the rubber contact failure, the wheels have a separate connector , so check continuity . The knobs are mainly not always active except tuning and volume so check sofware pages before.

I believe the parameter value should change even if the value button is not pressed. I noticed from the schematic that the value pot as well as the pitch and mod pots all get muxed through the 4051 mux component. I put an oscope on the output of the mux and I do see level changes when I rotate any of the pots. That tells me that the mux is functional. I’m wondering if the 311 comparator that is fed from the mux output is bad. Interestingly, it is one of a few components that are socketed.

I fixed the problem by replacing the LM311 comparator IC. All knobs and pitch/mod wheels work great now, although the value LED will not light. Not a big deal, but I’m wondering how that could be related to the LM311 going bad.


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