Green Omeg ECO pots in a 2001 TB3030 - replacement options

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FactoryDefault
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Green Omeg ECO pots in a 2001 TB3030 - replacement options

Post by FactoryDefault » Sun Feb 17, 2019 1:05 pm

Hello wigglers, I'm hoping someone can help me with this puzzle. I have an issue 2 TB3030 that I built in 2001. I still use it but I've been opening it up to clean and lube the pots every 12 months or so. The last cleaning did not deliver the results I expected. :hmm: It still has the original green omeg eco pots in it because I bought the knobs and designed the front panel around them and it's proving hard to find anything else that will fit. There are a couple of challenges:

Challenge #1 - The holes in my front panel are not round. They have flatted sides to stop the pots from turning so the pots need to have flat spots on either side of the threaded bushing. This doesn't seem to be a common feature of currently available pots. I see one bourns pot (39SB-1RB-103) with this feature but they are $13 each :sad:

Challenge #2 - the shaft needs to protrude at least 20mm (i.e. 7.5mm bushing plus 13 mm shaft) from the body of the pot in order to reach the set screw on my knobs. The alpha/mammoth pots that are available all seem to fall short of that by a mm or so. I paid a fortune for the knobs (multicomp MC21034) so I'd rather not abandon them but if I have to I will.

As far as I can tell, I'm faced with these choices:

1. Buy 16mm alpha pots, drill out the holes in my panel or file off the sides of the pot's bushing and buy new knobs that will accommodate a different/shorter shaft.

2. Find some other pots that will fit without modification. Help!

3. Buy another set of omeg eco pots (they still make them so how bad can they be?)

Any suggestions? :despair:

Thanks in advance.

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Synthbuilder
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Post by Synthbuilder » Mon Feb 18, 2019 6:55 am

I've always used Alpha pots in my Omeg pot replacement jobs. Two problems are encountered. The bush size is a lot smaller, approximately 7mm compared to 10mm. This probably means that the roundness of the Alpha's shaft won't be a problem and the supplied pot washer should be big enough to cover your much larger panel hole.

Alpha pots do seem to be available with different shaft lengths. Rapid Electronics' ones seem to be longer than Banzai's for example.

The biggest problem is that Alpha pots and Omeg pots do not have the same footprint. The three pins are the same spacing but they are not in the same place with regards to the front of the pot.

Omeg still make the P16 Eco and Piher do their PC16 which I think is equivalent.

Tony

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FactoryDefault
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Post by FactoryDefault » Mon Feb 18, 2019 2:23 pm

Synthbuilder wrote: Piher do their PC16 which I think is equivalent.
I haven’t seen those before.

Looks like they have the flatted bushing and a long plastic shaft that I can cut to length.

Thanks Tony!

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Noiseconformist
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Post by Noiseconformist » Tue Feb 19, 2019 12:17 pm

Synthbuilder wrote:The biggest problem is that Alpha pots and Omeg pots do not have the same footprint. The three pins are the same spacing but they are not in the same place with regards to the front of the pot.
I'm following your advice, mounting the Alpha pot body turned downside up (i.e. by 180°) and wire the pins to the PCB.
It's some extra work, but it's fine.
Michael.

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FactoryDefault
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Post by FactoryDefault » Thu Apr 04, 2019 10:25 pm

Just a quick follow up on the pot replacement.

I went with the alpha 16mm pots. Mouser had all the right values with a round 1/4" x 20mm shaft apart from the dual 50k which I got in 24mm with a 1/4" x 0.335" shaft.
I 3d printed some adapters to stop the pots from moving around in the flat-sided holes.

My old knobs wouldn't fit the new pot shafts so I visited the local electronics surplus store.
They had some black aluminum knobs that worked and it all turned out great!

Image

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