I have an issue with the pitch wheel pot on my mini. It seems to pull the tuning out after bending. I checked the wheel and it is tight on the pot, so there is no slippage. I think maybe the pot might be centered at the wrong place. Does anyone know if the pot is scaled differently at different positions, like how some pots have most of their effect towards higher end of their travel?
Since I have never serviced/calibrated it, (though never had tuning problems before) when I switched the mod and pitch wheels when the pitch detent was worn I used the pitch pot to tune the a440 at the center of the tuning knob. I think maybe this re centered the pitch wheel pot and now it throws the tuning off. I think it may be too sensitive.
I will probably calibrate it soon, but I would like to get the pot working correctly first, so my question is where in the pitch pots travel should the center be?
Take a DMM and measure the pitch bend pot resistance at the wiper (center pin) relative to ground. It should read between 15K and 15.6K ohms at the detent notch position (center) according to the service manual.
edit: it might also be a bad or intermittent contact on that pesky Cinch-Jones connector to the mod wheel assembly…
BTW, the pot for the pitch bend wheel is 25K ohms linear. No exponential behavior should be coming from it depending on its position.
On my Mini, the pitch bend goes from -7 semitones to +8 semitones, from center notch. But in the manual, it says that the range should be +/- 5 semitones minimum.
Thanks. So if there is no exp behavior, then the 16k is just arbitrary? So I guess it could be just a solder point?
Remember that the pot is not moving on its whole range, but only about 90 degrees. So that’s where the 15 to 15.6K value at center notch must come from.
I strongly suspect the Cinch-Jones mod wheel assembly connector, making intermittent contact. I had the same problem once, pitch bend not returning to same note, and was fiddling with the actual plastic wheel moving it on the shaft to try to get it back to proper place, thinking it could have slipped. Until I slowly moved to two halves of that connector while holding a note… Geez… The pitch was all over the place!
After cleaning it carefully, and positioning the mod wheel so that when at detent the pot measured 15K, everything was back to normal again.
edit: what you could do, without dismantling the synth, is to remove only the mod wheel assembly. Taking it out just enough to reach that connector, and move it while a note is playing. You’ll hear right away if it’s the culprit.