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September 30, 2014, 11:52:58 AM
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DIYstompboxes.com  |  DIY Stompboxes  |  Building your own stompbox  |  center tapping a pot 0 Members and 1 Guest are viewing this topic. « previous next »
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Author Topic: center tapping a pot  (Read 2405 times)
Dan N
Posts: 1076

Dan N


center tapping a pot
« on: July 07, 2007, 06:18:06 PM »

Not the most useful skill, as so few circuits use tapped pots. The Korg MS04, Ibanez PM7, and Boss PC-2 are the only ones I've ran into. Anyway, I made this fast and nasty tutorial:

http://users.rio.com/senorris/junk/ct/ct.html

Better ideas would be lovely...
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markm
Posts: 3953


Mark M.


Re: center tapping a pot
« Reply #1 on: July 07, 2007, 06:21:11 PM »

Ha!!
That's Cool!   icon_cool
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stm
Posts: 1117

Sebastian - Chile


Re: center tapping a pot
« Reply #2 on: July 07, 2007, 06:28:02 PM »

Interesting! Thanks for sharing.
I understand this type of pot is key in high end equalizers.  Wouldn't know where to get one.
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The Tone God
Global Moderator
Posts: 5298


Maggie


WWW
Re: center tapping a pot
« Reply #3 on: July 07, 2007, 07:18:26 PM »

The same technique can be used in some amps' bias adjustment pot.

Andrew
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Dan N
Posts: 1076

Dan N


Re: center tapping a pot
« Reply #4 on: July 07, 2007, 07:32:09 PM »

Wouldn't know where to get one.

Funny, I have an old Radio Shack dual 5K stepped pot with 40% loudness tap. Cat. No. 271-1730. It's from a lot of old RS parts, so perhaps discontinued.
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Paul Marossy
Posts: 12527


Just Another Guitarhead


WWW
Re: center tapping a pot
« Reply #5 on: July 07, 2007, 07:51:15 PM »

Hey, that's a pretty cool idea!  icon_cool
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_/\_/\_PJM_/\_/\_

www.diyguitarist.com
www.soundcloud.com/Paul-Marossy

"Tone is in the fingers."
Paul Perry (Frostwave)
Posts: 7470

Paul P.


Re: center tapping a pot
« Reply #6 on: July 07, 2007, 08:04:11 PM »

One thing a centre tapped linear pot is good for: more flexibility with a LFO.
instead of having a tri/square switch and a depth pot, you take the tapped pot, run square to one end, tri to the other, ground the centre tap, and now as you turn the pot the modulation goes from full square then less depth of square than no mod then the tri increases in depth. So you have saved a hole (or, you are able to make a mod without damaging the vintaj box). I have a bunch of 100K linear that were special ordered by someone on the synth-diy list, for this application.

That eyelet thing is beautiful, I have to say!! thanks for the tutorial, Dan!
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MKB
Posts: 119


Re: center tapping a pot
« Reply #7 on: July 07, 2007, 08:30:24 PM »

WOW, what a GREAT idea, thanks!!  Another good application is for building an all tube graphic EQ out of a Fender Super Twin Reverb amp; a very simple circuit but uses strange center tapped pots.  Now they are available!!
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R.G.
more
Posts: 16138


WWW
Re: center tapping a pot
« Reply #8 on: July 07, 2007, 08:39:43 PM »

From "The Secret Life of Pots", GEO, 8/99

Quote
Tricks you can play

This simple structure means that there are lots of non-standard things we can do with pots.

    * if you have a brand of pot that can be reassembled, you can swap wafers between pots to repair a broken or worn out one
    * if you have a dual pot body, you can assemble custom dual pots with wafers from other single pots of that same brand
    * if you have to repair a pot and don't have another wafer, any connection you can make between the two disconnected sections of pot will work
    * you can bend the wiper contacts sideways to let them contact new, unworn areas of resistive material
    * you can bridge over breaks in the resistive material with copper or silver conductive paint, or make a custom tap point
    * I have heard that you can use copier toner dust to melt over a section of worn resistor material and repair it.

You could hypothetically scrape material off the resistor band and make a higher resistance, odd taper pot, but there are better ways to do that.
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R.G.

Every single NASA manned mission starting with the Gemini series has carried a roll of duck tape.
Yes, really. Look it up.
Dan N
Posts: 1076

Dan N


Re: center tapping a pot
« Reply #9 on: July 07, 2007, 08:47:01 PM »

    * you can bridge over breaks in the resistive material with copper or silver conductive paint, or make a custom tap point

There we go. I still like the eyelet as a way to hook into the tap. 

Thanks for the response, guys!
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R.G.
more
Posts: 16138


WWW
Re: center tapping a pot
« Reply #10 on: July 08, 2007, 06:39:03 AM »

Oh, yeah! The rivet is a great way to hook to the tap. Much more solid than silver painting to a wire.
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R.G.

Every single NASA manned mission starting with the Gemini series has carried a roll of duck tape.
Yes, really. Look it up.
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