model d pitch wheel detent

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unfiltered37
Posts: 645
Joined: Thu Jul 07, 2011 1:28 pm

model d pitch wheel detent

Post by unfiltered37 » Thu Oct 06, 2011 7:08 am

Seems like it's loose or something. It won't return accurately to the correct pitch, perhaps because there's too much play in the detent. Any suggestions? I tried tightening the screw on the mechanism, but no luck. Maybe the recess in the actual wheel is worn?

mhuxtable
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Re: model d pitch wheel detent

Post by mhuxtable » Thu Oct 06, 2011 9:23 am

i would guess that the recess in the wheel is worn. after that many years of play, i'm sure its worn out by now. if you feel comfortable...open it up & look at the pitch wheel. then see if you can source a replacement.

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Kevin Lightner
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Re: model d pitch wheel detent

Post by Kevin Lightner » Fri Oct 07, 2011 4:38 am

It can be a worn detent, worn pot or both.
There are tricks that can be done tho.
Electrically, there's a way to create a "dead zone" area right around the center of the wheel, so even if the mechanical detent doesn't always snap into perfectly the right position, it won't matter electrically.
This mod however removes the ability to use the pitch wheel for manual vibrato or small pitch inflections.
Parts needed are two diodes (1N4148 or 1N914), a 27K resistor and an added wire to supply -10 volts for the mod.
(-10 volts is normally not present in the mod section and so a wire is usually connected inside to -10V somewhere and brought to the mod section area for the mod to use.)

Another trick is that you can swap wheels or turn them around so their detent area is "new" and never worn before.
The small metal pieces used as wheel stops (limit wheel travel) can be pushed through the wheel so they remain on the same side as they were before.

At times, I've even done all three to the same Mini.
A better mechanical detent, the electrical dead zone mod and a brand new pot (25K linear.)
But personally I think a new pot and decent mechanical detent will solve most problems like this.

PM me if you need the dead zone schematic, though I think I've uploaded it to synthfool.com or elsewhere too.
I can also provide a new pot already prepped for the job or a supplier and part number if you'd like to do it yourself.
But be warned upfront that the shaft of most new pots need to be shortened slightly or their shafts will hit the rear of the mod wheel pot. So you best be good with a file, sander, grinder or saw.

You can also try tightening the pitchwheel to the existing pot's shaft just a few millimeters away from where it normally lands from the detent.
This will provide a less used area of the pot for that centered area in the middle and the resulting small amount of tuning offset can be compensated for by retuning the VCOs slightly.
This trick doesn't always work perfectly, but it requires no new parts at all and is worth a try sometimes.

Finally, make sure the 12 pin connector to the mod section makes good electrical contact.
This is easy to check. Simply wiggle that connector around and listen for any pitch changes.
If bad, replacement is best but cleaning might work well enough too.

Good luck!
Better to be king for a night than schmuck for a lifetime. - R. Pupkin

unfiltered37
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Re: model d pitch wheel detent

Post by unfiltered37 » Fri Oct 07, 2011 5:29 pm

Thanks for the response. It turns out the tiny hex screw hidden in the wheel was loose. I didn't even know it was there. I turned the wheel around like you said, hammered down the metal stoppers and tighted the screw, good as new. I can actually control the pitch way better now, glad it happened. Got the mini going through a space echo, sounds killer!

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museslave
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Re: model d pitch wheel detent

Post by museslave » Fri Oct 07, 2011 6:37 pm

My detent feels like a chasm. I'd like a Micromoog ribbon instead. : )
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Technician Larry
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Re: model d pitch wheel detent

Post by Technician Larry » Wed Oct 19, 2011 5:11 pm

Image

This is the pitch bend detent cone and mounting screw from the Solovox Memorymoog. The cone is so badly worn that the mounting screw tip was exposed and gouging into the wheel. Carl's Moog came back for autotune failure again - see the full report here: https://www.facebook.com/photo.php?fbid ... 525&type=3

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