Tapping a pot?

[Chuck H]

Anyone know a clever way to tap the carbon film resistance strip on a pot that's somewhat durable and won't get in the way of the wiper?

TIA

[Leo_Gnardo]

I've thought of that but never attempted it. If you're trying to say, replicate the tapped treble in brown Fender EQ stack, Hoffman has tapped 250K. IIRC they have non standard bushing and PC leads but they're the only tapped pot I've ever found for sale currently.

[catalin gramada]

There are a lot of electric conductive paints, glue, gels, etc on the market. Think it worth to try with.

[Chuck H]

Thanks. Yepper, I know about those. I've found a bunch of other cool stuff in my searches too, but this is a pretty custom project I'm working on. I'll need a dual ganged 500k log pot with both tracks tapped at 50% resistance. Believe it or not I did find a linear taper like this! But I need an audio. Or rather, I need to make one it seems.

[Chuck H]

There are a lot of electric conductive paints, glue, gels, etc on the market. Think it worth to try with.

Yes. And thank you. I read about using such products on R.G.'s GEO article:

http://www.geofex.com/Article_Folder...s/potscret.htm

But I'm not sure how to make such a connection durable/solderable/etc. so I was hoping for practical experience.

[catalin gramada]

If are good enough to replace a soldering job ,I think will be good enough to make a bridge between carbon trace and a mechanical point. There are also markers , can draw a whole circuit with it, just do some investigation to see what fit You demands

First page I opened: https://www.amazon.co.uk/Bare-Conduc.../dp/B00CSMDT8S
I.m sure are thousand of products available on the market

[Leo_Gnardo]

I'll need a dual ganged 500k log pot with both tracks tapped at 50% resistance.

Then have a look at hi fi offerings. That kind of pot would be used in stereo preamps that have a "loudness" switch. Not sure about the 50% figure. But it's worth a search.

[pdf64]

I think that the 1M master vol in pull boost TRs has a tap around there. The pull switches are starting to fall to bits now, but if you can find one, the track etc may be salvageable, and other parts could be canibalised from a new CTS pot.

[Pedro Vecino]

I see it possible to do it on a 24mm potentiometer. With a thin solid cable (I have used one with a diameter between 1/3 and 1/4 mm.) inserted under the track to obtain pressure and bent over it. Then fixed with a light touch of a suitable conductive glue. Just enough to adhere it and that the cursor finds a soft ramp when crossing it (you would need an ultrafine brush and make trials in others).
Even without it I do not notice nothing strange in the cursor when turning it.
After that it would only be necessary to make a small hole in the housing of the potentiometer to take it outside.

[galaxiex]

I'm just spitballin' here...
but I'm thinking very thin copper or brass sheet like shim stock. .001" or .0015" or maybe thicker? .003"?

Somehow slipped under the track, if you can get the track away from the wafer without damage + conductive adhesive or even super glue.
Could then solder a wire to the shim stock to bring outside the pot.

[The Dude]

If you can without giving away any trade secrets, what's the circuit? I'm thinkin' there must be an alternative way of achieving your goal. I don't like the idea of making parts. If they fail, you're screwed or you have to get them rebuilt/remade.

[Chuck H]

That's good! Most of the pots I've opened don't have a resistance strip you can get under. A thin piece of copper glued to the resistance strip with conductive adhesive is something I can solder a thin wire to. Probably right at the edge so it won't even meet the wiper. I'm thinking I'll tie an overhand knot in the wire to act as strain relief and run it through a hole drilled in the case. Now I just need to find a dual 500k log pot that will allow me access to both resistance strips.

[Chuck H]

If you can without giving away any trade secrets, what's the circuit? I'm thinkin' there must be an alternative way of achieving your goal. I don't like the idea of making parts. If they fail, you're screwed or you have to get them rebuilt/remade.

Still a trade secret for the moment. I wouldn't be making these things to sell, but I do want to build some working prototypes before I seek a patent and put together a prospectus to shop around.

[nevetslab]

You might be able to slip in flattened 30AWG or smaller wire underneath the resistance track of OMEG pots. I've never tried this tapping approach, but here's some photos I have of a disassembled OMEG pot, I think from a Vox amp.



Getting a dual-gang pot apart and then re-assembled.....most I won't tackle....made for assembly only.

[catalin gramada]

Bothered too much. Drill a hole at border of track, hook a wire through to ensure mechanical stability, put a drop of conductive smack and is done.