Repairing original ICAR pot in '60s Vox wah

[soapfoot]

Wah pedal obsessives love to talk about the old Italian ICAR pots used in the Thomas Organ wah pedals from the late '60s. It's a bit of a bizarre taper, and nothing else is really like it. But like all old carbon pots that undergo zillions of cycles, they wear out.

They're marked "100k," but they almost all read 2x or even 3x that value now, and mine was no exception (closer to 280k).

I had one that I eventually couldn't make non-crackly anymore, so I replaced the pot with a modern reproduction. The pedal wasn't really the same. I put the old pot in a drawer in a rare moment of intelligent foresight.

Fast forward about 15 years, and today I disassembled the original pot (carefully!) and accessed the carbon resistive element and wiper. The wiper looked gold plated, and was free from corrosion. The carbon wasn't in the best shape, but I cleaned it up with some Blue Shower on a Q-tip, and then lubricated it with Caig F5 fader grease.

After reassembly, the sound of the pedal was back, and the crackling was much improved... but still not perfect. So I disassembled the pot once more (hopefully the last time!). Taking a pair of tweezers, I bent the wiper (actually, two mating surfaces!) onto a fresher bit of carbon. This did the trick! It's like a new pot now, and I'm pretty psyched.

In the attached picture, you can see that the resistive element is made of two different materials--one normal-looking dark carbon, the other much lighter (almost metallic) with a diagonal transition between the two materials.

The lighter-colored material appears to offer almost no resistance at all. The pot measures about 286k throughout the portion of the travel over the darker material. The lighter material is a total of about 5 ohms. Consulting some wah experts, this is apparently completely normal for an ICAR pot. It behaves a bit like an extreme S taper, with the darker material seeming like a standard audio taper, and the lighter colored material offering very little resistance beyond that point.

Picture attached

 

[Whoops]

Cool idea to bend the wiper so it touches a different place of the carbon track.
So that solved the crackling but how about the total resistance being almost 3x of the original value?
Doesn't it change the way the rocker pedal affects the circuit?

What was the modern reproduction pot you used?

 

[soapfoot]

Apparently, all ICAR pots are high now, and what seems to be true is that either:

1) they were always way higher than the stated value and mislabeled (either intentionally or not)

2) they’ve aged in a way that people like and associate with vintage wah pedals

3) the actual value isn’t all that critical

I know that many of the replacement ICAR reproductions out there are 200k parts to account for this

In any case, the pedal sounds fantastic—I wouldn’t change a thing!

I don’t remember who made the reproduction… I got it on eBay about 15 years ago from someone in Israel who had a short run of pots made to duplicate the ICAR taper. It was pretty good! The pedal worked and sounded good. But it’s better with the reconditioned old part

 

[Whoops]

I don’t remember who made the reproduction… I got it on eBay about 15 years ago from someone in Israel who had a short run of pots made to duplicate the ICAR taper. It was pretty good! The pedal worked and sounded good. But it’s better with the reconditioned old part

I'm asking this, because at the present there's many companies doing true ICAR pot taper's,
maybe it was not the same 15 years ago but nowadays there's a lof of good options.

The Fulltone ICAR pot is supposed to be really good:

"Fulltone Wah Pot
The Fulltone Wah Pot (FWP) is the same pot used in our CLYDE Standard & CLYDE Deluxe pedals, and is an exact reproduction of vintage 60's and early 70's Icar pot found in the wahs used by Clapton, Hendrix, Page, Schenker, etc."

https://www.fulltone.com/products/fulltone-wah-pot
but there's also some other good ones made by CTS and other, I leave the link here for future reference:
https://www.banzaimusic.com/Wah-Pots/

 

[soapfoot]

Teese also makes (made?) one that's supposedly very good. Many of them are probably "close enough," especially for a new build or clone.

But I had this original sitting around, and I always loved the way the pedal sounded before it became too-far-gone. Now I have that exact sound back.

And since it's a working pedal that's now all-original, it's objectively more-valuable (though I'm not interested in moving it on)

 

[Whoops]

Cool
have fun