Volume pedal pots

David Deratany · Post by **David Deratany** » 6 Jan 2005 5:22 am

I've just started getting a hum in the middle of the travel on my volume pedal. None at the beginning and none when fully engaged. Is this a sign of wear or nothing more than perhaps a solder joint needing to be refreshed?

What is everyone using these days? Are the Allen Bradleys back to their early quality or is some other brand being used now; and where might I want to purchase a replacement?

Farris Currie · Post by **Farris Currie** » 6 Jan 2005 8:18 am

Nashville Steel Guitars, Bobbe Seymore

John Daugherty · Post by **John Daugherty** » 6 Jan 2005 12:34 pm

David, I can't believe that a pot is the problem. Connect the guitar directly to the amp and see if it still hums. If so, you have a bad connection in the guitar or the pickup is picking up hum from a nearby AC line.
If there is no hum when the pedal is not connected, suspect a bad connection in the pedal. Loosen and retighten the nuts holding the jacks to the pedal. Clean the contact surfaces of the jacks(put contact cleaner on a plug and push it into the jack several times).
You should also try some different cords.
Let me know what you find.........JD

Paul Osbty · Post by **Paul Osbty** » 6 Jan 2005 3:00 pm

I recall a similar, but not exact, problem.

It may be that the ground of the pedal's potentiometer is not good. The pedal is now acting as a series resistance, or a rheostat.

When you are at half deflection you may be at the maximum power transfer point which yields the most current, hence the most noise.

John Daugherty · Post by **John Daugherty** » 6 Jan 2005 4:49 pm

It is my thinking that if the ground connection to the pot broke, you would be at near full volume all the time. The pot would not be able to shut the signal down. In that case, the minimum signal level would be determined by the input impedance of the amp.....JD

David Deratany · Post by **David Deratany** » 7 Jan 2005 6:48 am

As I thought about this more, it occurred to me that:

One of the cords I used may have been a speaker cord that looks like a regular patch cord but is not shielded; I will check this first, and if not the cord, I will check the solder joints. I can't say one has never gotten past me.

Thanks, all, for keeping me on track. Given what these pots cost these days, I'd just as soon not buy one only to have it sit on the shelf. This pedal is for guitar; I have two others for my steels and can always use one of them to get me out of a jam.

David Deratany · Post by **David Deratany** » 10 Jan 2005 5:15 pm

As it turns out, my hunch was right. One of the patch cords I used was for speakers and not shielded. I do wish they'd make them so they could be easily distinguished. I tried a proper cord and the pedal behaved as it should

Again, my thanks to all who took the time to help me out.

jim milewski · Post by **jim milewski** » 11 Jan 2005 7:13 am

It could be that part of the travel is moving the pot, make sure the locking nut is tight and you may have a momentary loose solder joint, resolder all three joints

John Bechtel · Post by **John Bechtel** » 11 Jan 2005 12:39 pm

I'll make my offer again! Rather than throw-away ‘old, worn-out AB 500K audio-pots’, mail them to me and I'll return your postage (x2).
John Bechtel
1508 Dickerson Pike
Lot H–18
Nashville, TN 37207
I like scratchy-pots!

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“Big John” Bechtel

David Deratany · Post by **David Deratany** » 11 Jan 2005 2:28 pm

Now you tell me after I threw a couple away when I moved this past summer

John Bechtel · Post by **John Bechtel** » 11 Jan 2005 6:42 pm

David;
I made the offer a long time ago and some said they would send some, but; I never received even one! All I ever got was some people wondering why I would want scratchy-pots! They can be repaired!

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“Big John” Bechtel