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My Optigan has unstable pitch. Is there hope??

Posted by peahix on March 15th, 2008

Pitch stability is one of the biggest problems for Optigans. The rubber on the idler wheel gets hard or worn over the years, which makes the wheel slip against the tapered motor shaft. Old wheels can have other problems including notches or flat spots, which cause a knocking or grinding sound when the discs are played. I’ve tried to recondition the rubber and restore the gripping surface with chemicals and fine sandpaper, only to have the pitch problems return a few weeks later.

I recently came across the web site of fellow who says that he completely replaces the worn and damaged rubber on pinch rollers and drive wheels in tape recorders. On the site he shows several examples of his work along with a wow and flutter test comparing a repaired pinch roller to a new one. Since his price seemed reasonable and I had a spare idler wheel, I decided to give him a try.

After about week I received the repaired wheel. The wheel was clean and the rubber had the correct wedge-shaped profile (I sent him a copy of the original Optigan blueprint for the idler). I disassembled the Optigan and removed the shaft/wheel assembly only to discover that the wheel is secured to the shaft by crimps on either side of the wheel. I have a small lathe, so I chucked up the shaft and carefully filed down one of the crimps to remove the old wheel. I slid on the repaired wheel after applying oil to the shaft. I then secured the wheel to the shaft with a clip and reinstalled the wheel/shaft assembly into the Optigan.

I tested the wheel using the new Mod Rock disc. It played well and there was no change in pitch during the several minutes of play. I then put in an old Optigan disc that used to slip badly, and the pitch stayed stable like the Mod Rock disc. I then replaced the Mod Rock disc and played with the pitch control. I was amazed to discover I was able to adjust the pitch about 10% lower and higher than before. I’ve had the Optigan working for a week now, and it’s holding up nicely. I’ll publish an update in a few months. I am optimistic that this will hold up for many years.

The fellow’s name is Terry Witt and the web site is The charge for rebuilding the Optigan idler is $35 plus shipping ($5 for the USA). I have been discussing the possibility of Optigan owners sending in the wheel/shaft assembly without having to go through the difficultly of removing the wheel from the shaft. He is willing to look at this and he’ll need to see one to determine what is involved (may or may not affect the price).

If you intend to send your wheel to Terry and you’ve never disassembled an Optigan, you may want to pick up a copy of OptiDocs from for instructions. Let us know if you use his services, and please post your results.


2 Responses to “My Optigan has unstable pitch. Is there hope??”

  1. Danny Dunlap Says:

    I just got my idler wheel back from Terry. Quick turn around and I sent it on the shaft. Terry was able to remove it from the shaft resurface the wheel and put a metal collar on to hold the wheel back in place. I was a bit confused when I tried to reinstall but quickly realized he had put the wheel back on backwards. Flipped it around and popped the wheel and shaft back into place and what a glorious sound! Most solid optigan pitch that I have ever experienced. Although I will say that to get it to proper pitch I need to go well above the middle area of the tuner dial. So i can’t slow it down below pitch as much as i could before. A little bit of a drag but I’m sure I will be using REAL optigan much more now that it can hold a pitch for more than 15 seconds. Thanks Terry! And thanks Pea!


  2. peahix Says:

    hi danny, thank robert for this tip! glad it’s working well!

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