The desperate hunt for a potentiometer

[neoflox]

Hey guys,

My longest owned pedal, a Maestro Parametric Filter fell victim to its age. One of its potentiometers bit the dust about three years ago and I can't find a replacement part for it anywhere. By now, I am willing to pay good money to get something fitting to bring it back to life. Maybe someone here has an idea or maybe the right part lying around…

• 24mm diameter
• 100k DUAL rev log
• solder pins
• 6.35mm shaft
• 9-10mm thread length

I have tried using a modern Alpha part of the right values but it won't fit in the enclosure due to a shorter thread and shaft. I even contacted CTS about the part but it's a custom part and I'd have to order some thousands of it to get it made at all.

What's broken is the resistance coating on the inside. So maybe I can be helped with any 100k rev log potentiometer of the same making and transplant the part

Anyone?

[lordgalvar]

Have you tried to make your own resistive substance and just referbishing the pot? I would think you could probably get make a new "Plate" and then coat a homemade substace on it. Then rebend the tabs back over?

http://electronics.stackexchange.com/questions/24420/how-can-i-make-my-own-potentiometer

I found that site. It seems like it would be a try and see kinda thing. But it might be the cheapest option.

Epoxy mixed with graphite seems like it might work.

[lordgalvar]

http://www.diystompboxes.com/smfforum/index.php?action=printpage;topic=69848.0 -> talks about the same issue.

http://www.ebay.com/itm/100K-OHM-Linear-Dual-Taper-Rotary-Potentiometers-B100K-100KB-POT-ALPHA-/260944291837 -> though it is 16mm but maybe?

http://www.ebay.com/itm/2x-ALPHA-C100K-Dual-Stereo-Potentiometer-Log-Taper-pots-/170532518825 -> similar to the last one.

I don't know. I gave it my best shot.

[HorseyBoy]

^ Those dual pots always put me off going for old fuzz-wah pedals (like the Colorsounds) that use them. When the pot goes, there's no way to get another one.
Really, really hope you're able to source a new one or that you can bring the old one back to life, but if you can't, there's always the Stone Deaf PDF-1…

[neoflox]

Thanks so much for your best shot. Really appreciated. The 16mm pots don't help much since I need that special shaft and thread length to make it fit the enclosure. The post about the homemade repair sounds totally interesting. I'll have another read-thru tomorrow.

On a side note, I wonder what happened to old CTS pots after all? I remember searching through ebay 1-2 years ago for these and a lot of NOS pots came up. Now there is hardly anything at all… o.O

[moid]

musikding.de sell some CTR pots (but not the exact one you are after) http://www.musikding.de/CTS-Pots-24mm__filter--rev-log-C

I'm very new to pedal building, so feel free to say no to this - but isn't a rev log pot just the opposite to a normal log pot? Could you use a normal 100K dual log pot and the taper on the curve would just be flipped the opposite way around? (Please check this with someone who knows what he's talking about, I was reading this article : http://www.geofex.com/article_folders/potsecrets/potscret.htm which seems to imply that you can switch pots about... or maybe that's me misinterpreting it?)

If it is possible, then musikding sell a 24mm 100K log pot http://www.musikding.de/Alpha-Potentiometer-24mm-Stereo-100k-log_1 so perhaps you could put the longer shaft from your non working pot onto one of these and make the changes suggested in the article above to flip it to a rev log pot?

[neoflox]

hey, thanks for your input. everything you suppose is close and should be working, but it does not

• the new CTS pots have a different design than from the 70's and I can't use them for spare parts
• rev log is like log but the other way around, correct. I'd love to find one of these but unfortunately, finding rev log or log is equally hard and not the pressing issue here. It's the shaft/thread design or the exact design of the resistance part inside
• tried the Alpha. Works okay, but the shaft is too short** – I can't attach it in the enclosure or to the knob.

Thanks anyways!

**yeah, twss

[mysteriousj]

http://www.digikey.com/product-detail/en/KKB1041S28/KKB1041S28-ND/770972

This is pretty close, but the problem is it's non stocked and you need to purchase at least 25 of them. Wouldn't be so bad if they were a dollar each.. try 35 each? You could maybe get it from elsewhere..

http://www.mouser.com/ProductDetail/TT-Electronics/P092N-FC25CR100K/?qs=56eeD6vBg8h14rooCrSgaA%3d%3d

This is about as close as I could find. As in it's a 100k rev log. It is a 9mm pot though so a lot smaller, wire it in and create some kind of mounting for it? If Mouser/Digikey doesn't have it it's pretty much a unobtainium custom part.

[neoflox]

Hey, that first one looks interesting! Thanks a lot, I'll try to find another source of it!

[spruce_moose]

If Mouser/Digikey doesn't have it it's pretty much a unobtainium custom part.

Have a look in some old car radios! Might be a needle in a haystack. Junk shops have piles of those things now. I do recall pulling some apart once and coming across a bunch. Mostly 10k though..

I didn't find it too hard to transplant a track into a VP Jr when I wanted to make it a 10k and found it wasn't a standard pot. Those things are bastards to put back together.

[spruce_moose]

It is a 9mm pot though so a lot smaller, wire it in and create some kind of mounting for it?

I'd say that's a good option. No one would see the wiring!

[lordgalvar]

Found these guys...http://www.omeg.co.uk/profile.htmthey seem to do mostly custom work, but maybe (and sell off what you don't need, people do look for them)