Weird tone pot problem

Moses Talbot

Member
Messages
14
I replaced the stock tone pot on one of my guitars with a push/pull pot wired to give me series/parallel on the bridge humbucker. That works fine and is not the reason for this post.

The weird thing is that when I turn the pot up to 100%, it sounds like it's at 0%. When I turn it to 0%, it sounds like it's at 0%. When I turn it to 50%, it sounds like it's at 100%. So in other words, the 100% "sound" is in the middle. Obviously, that's not as easy to use as the traditional way.

Does anyone know if this is a wiring problem or is it possibly a bad pot? It's got a linear taper, if that matters at all. (No, that's not what I would have preferred for this application.)
 

Albert_bcn

Member
Messages
24
Linear pots work that way in a tone circuit. You need an Audio (or Log, different name, same thing) pot.
 

Moses Talbot

Member
Messages
14
That is very odd because I bought them in a 2-pack. The other one works as expected. Most of the tone rolloff is in the 0% to 50% range, but it continues on up to 100%.
 

Albert_bcn

Member
Messages
24
Linear pots on tone circuits don't do anything from 10 to 7 and then from 7 to 8 they "switch on".
Do you have the part reference?
 

testing1two

Platinum Supporting Member
Messages
2,500
I replaced the stock tone pot on one of my guitars with a push/pull pot wired to give me series/parallel on the bridge humbucker. That works fine and is not the reason for this post.

The weird thing is that when I turn the pot up to 100%, it sounds like it's at 0%. When I turn it to 0%, it sounds like it's at 0%. When I turn it to 50%, it sounds like it's at 100%. So in other words, the 100% "sound" is in the middle. Obviously, that's not as easy to use as the traditional way.

Does anyone know if this is a wiring problem or is it possibly a bad pot? It's got a linear taper, if that matters at all. (No, that's not what I would have preferred for this application.)
An inexpensive multi-meter will answer this for you and it's an invaluable troubleshooting tool for guitar wiring. You just need to measure the DC resistance of the pot at "10" and "5" and "0" to see if it is defective and to identify it's taper.
 
Messages
994
...turn the pot up to 100%, it sounds like it's at 0%. When I turn it to 0%, it sounds like it's at 0%. When I turn it to 50%, it sounds like it's at 100%. So in other words, the 100% "sound" is in the middle...
Sounds like both ends of the track are grounded, and capacitor is connected to wiper. Thus highest resistance presented to capacitor is when the wiper is at middle of the track (125kΩ at middle given 500kΩ pot (250kΩ||250kΩ)).

Is one track lug touching something it shouldn't? (Braid? Component leg? Cavity? Etc.)
 

Albert_bcn

Member
Messages
24
Sounds like both ends of the track are grounded, and capacitor is connected to wiper. Thus highest resistance presented to capacitor is when the wiper is at middle of the track (125kΩ at middle given 500kΩ pot (250kΩ||250kΩ)).

Is one track lug touching something it shouldn't? (Braid? Component leg? Cavity? Etc.)
You are right!

Moses Talbot, you should make sure that the terminal labeled "3" of your pot is not touching or connected to anything. That includes the pot case.
 

Moses Talbot

Member
Messages
14
Sounds like both ends of the track are grounded, and capacitor is connected to wiper. Thus highest resistance presented to capacitor is when the wiper is at middle of the track (125kΩ at middle given 500kΩ pot (250kΩ||250kΩ)).

Is one track lug touching something it shouldn't? (Braid? Component leg? Cavity? Etc.)
That was exactly it. I was following the diagram at Push-Pull Pots - How They Work, Wiring Mods, and More! (fralinpickups.com) - mod #4 - and it sure looks like they want me to wire it to #3. I moved it to #1 and it works perfectly. Thanks for your help everyone!

Let me guess, you're going to tell me that the Fralin push-pull pots are wired some other way.
 
Messages
994
...mod #4 - and it sure looks like they want me to wire it to #3. I moved it to #1 and it works perfectly. Thanks for your help everyone!

Let me guess, you're going to tell me that the Fralin push-pull pots are wired some other way.
Glad you worked it out.

Mod #4 was attaching the series/parallel switching to a volume pot, not a tone pot, so it need a little massaging to work with a tone pot, couldn't be copied exactly as was.

Anyway, all ends well.
 




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