Hi everyone,
My acorn masterkey 49's pitch wheel was having some issues recently. It was wavering and jumping in pitch, and wouldn't return to an in-tune rest position.
I decided I should try opening it up and replacing the potentiometer, so I did exactly that and ordered a new pot that seemed to match the same specs: same resistance, both 300 degrees travel, same shaft length and diameter. I resoldered it and put it back together. Generally it all works correctly now, except for one big issue - the range doesn't seem to be matched correctly. When I push the pitch wheel all the way up, the computer only reports about a 1/6th rise in the wheel. And the same bending down.
Can anyone help explain why this might be? Have I simply ordered the wrong pot?
Thanks,
Stephen
Pitch Bend Wheel Repair Issue
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crochambeau
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Re: Pitch Bend Wheel Repair Issue
It might just need calibration, but I haven't the faintest clue about how to go about that.
Did you compare or measure the removed part to the installed part?
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stephenmoroz
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Re: Pitch Bend Wheel Repair Issue
I'm not sure about calibration either. I've checked the manual and it doesn't say anything about calibrating the wheels.
Could you clarify what you mean by "measure"?
There's a small screen on the keyboard itself that displays the midi values that are being sent, and the pitch bend reports from 53 -> 76 with 64 being the centre point. So it's got the centre point correct, but it's clearly not reporting the full range of 0-127.
Could you clarify what you mean by "measure"?
There's a small screen on the keyboard itself that displays the midi values that are being sent, and the pitch bend reports from 53 -> 76 with 64 being the centre point. So it's got the centre point correct, but it's clearly not reporting the full range of 0-127.
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crochambeau
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Re: Pitch Bend Wheel Repair Issue
The physical part has three legs, using a multimeter (or Ohm meter) measure across the outermost legs. This will give you the total resistive value of the potentiometer.
You can go further, and rotate the shaft to a center point, and then measure from the center leg to one outer leg, followed by measuring from the center to the other outer leg. Chances are, the values would be similar (indicating a linear taper).
None of your troubles indicate a wrong taper, but knowing the over-all value can be informative. For example, if you installed a 100K (104) and the original part was a 10K (103) that could conceivably cause confusion at the micro-controller input that produces the MIDI information.
Regarding calibration, that's probably tucked away in service data, not user manuals. Could also be an automated thing that just happens in a factory reset. It really depends on how the code has been set up.
Good luck with it!