Is my pot going bad?

Roger Rettig · From: Naples, FL

I had a recent issue with my ancient Goodrich pedal when the string broke (while doing a TV!) It's given sterling service now for many years, although Herby replaced the pot for me in 2000.

Now I'm getting a slight break-up in the signal, especially when I first switch on my gear and start to play. It's been going on for a couple of weeks now. I checked my cords and all seems well there so, just now, I changed to my other Goodrich v/p and the problem's gone!

Is this a pot starting to fail? I should know, but problems are so rare that one's memory can be faulty and it's hard to recall the symptoms. I guess ten years is a pretty good performance for a pot that works as hard as mine does!

I have just these two v/pedals - I'm thinking of getting a third!
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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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Mike Wheeler · From: Delaware, Ohio, USA

Well, Roger, if you change out the cords one at a time and the problem remains, and then you change out just the pedal and the problem goes away, it has to be the pedal. One last possibility is that the internal wiring may have a problem...like an intermittent connection, or cold solder joint.

But, being 10 years old, and heavily used, it is likely that the pot has simply worn out.
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Best regards,
Mike

Roger Rettig · From: Naples, FL

Thanks, Mike, but the deceiving factor here is that, after I've been playing for a fairly short while, the problem seems to go away. Therefore, during the lengthy process of switching out cords to check if they're responsible, the symptom disappears and I'm none the wiser!

Bit like going to the doctor, really, or taking your car to the shop and being unable to make it misbehave when the guy's watching....

I'm set up with my 112, Profex, VP and steel, by the way.

It does seem to be the pedal as it hasn't done it since I switched out with my other Goodrich. I know, I know - I've answered my own question, but I'm really asking 'what are the symptoms of a pot going bad?'.
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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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David Nugent · From: Gum Spring, Va.

Roger...A pronounced scratching sound through your amp is normally the first and most common indication of a pot going bad. If this is not present, you may want to check for other problems such as wiring. Normally, when a pot goes bad it does not remedy itself over time (unless disassembled and lubed).
Just a thought...If not already doing so, you should rotate your pedals so that both are used equally. When a pedal is not used over a period of time and stored in one position, a flat spot may develop in the pot resulting in the scratching noise I mentioned earlier.

Roger Rettig · From: Naples, FL

Thanks, David.

To be honest, when I'm out playing (I usually am working solidly for five or six months at a stretch) I don't pay any attention to which pedal I use - I just grab the handiest one. I'll pay a bit more attention in future.

This isn't quite a scratchy sound, but more like the contact is 'making and breaking' very slightly. It sounds just like a bad cord, except it isn't, 'cause I've checked them.

I use George Ls, and sometimes that little cap will work itself a little loose resulting in a poor connection, but I've gone through them all.
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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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Jim Cohen · From: Philadelphia, PA

Roger Rettig · From: Naples, FL

Mr Cohen strikes again!

Very Happy

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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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Kevin Hatton · From: Buffalo, N.Y.

Keep it in a humidor. It lasts longer.

Mike Sweeney · From: Nashville,TN,USA

Roger,

I had the same symptoms with one of my pedals last week. I fixed it by re-soldering one of the wires on the pot as it was a cold solder joint. Whoa!

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Zumsteel steel guitars, Telonics and Peavey amplifiers, GHS strings.

Roger Rettig · From: Naples, FL

Thanks, Mike...

I've looked inside and all the soldered joints - three to the pot and the ones to the jack-inputs - look solid enough. Can you tell just by looking?

Confused

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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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rpetersen · From: Iowa

Maybe a pot on the amp or input??? - Play with them a little
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Ron Petersen

Jim Palmer · From: fredericton, nb

Roger,your string may be slipping a tad.Might need some rosen on there so it will grip.

Dick Sexton · From: Greenville, Ohio

Roger,
A couple of good points, one, a cold solder joint may be visible, or it may not be. I would remove the old solder, and re-solder after cleaning the connections, if I thought a cold solder joint was the problem. I don't. But, if I went to that much trouble, I would replace the pot or at the very least clean the existing pot, that is of course, if it is the older Allen Bradley Mil Spec type. The newer pots (Tom Bradshaw type) get replaced, no questions asked.

The older Allen Bradley Mil Spec type data found on the internet, show that the older pots have a 25000 cycle life. If your 10 or so year old pot, has much less then that, it can be cleaned. This is not easy but doable. There are four metal tabs that hold the back on the pot body, they must be very gently pried up. They can break off if they are pried up to quickly. The back has been applied using a sealer like lacquer. Once the tabs are bent back, the back can be removed using a sharp bladed screw driver, working around the pot at the seam. When the back is removed, the pot can be cleaned using a contact cleaner type spray. I always run a small piece of paper between the rotor and the stator of the pot to clean under this contact. Once cleaned, I center up the rotor in its travel and replace the back. Again bend the tabs slowly or they may break. Once it is reassembled, I use a meter to to make sure all is well. You can reseal the back if you want, clear nail polish works well. Then reinstall your pot. At $35 to $50+ a pop, cleaning one of the older AB pots is my first option. I've done this many time with out problems. But always a good idea to have a spare pot just in case. Wish I was closer, I'd do it for you for a beer or a lesson, my pleasure.

Have a good day,
Dick Sexton

Roger Rettig · From: Naples, FL

Thanks for that, Dick - I'll confess that the procedure you describe sounds rather as though it's beyond me, but I'm sure the info will benefit others who would contemplate doing it.

One thing: The pot is still in place, and the only word I can see with any certainty die-stamped on the cover is: 'Clarostat'; does that tell you what sort it is or not?

Your help is much appreciated!
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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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Dick Sexton · From: Greenville, Ohio

Yes, Roger, it is not an Allen Bradley. I've not cleaned one of those and am not sure if they can be. Also, I'm not familiar with the cycle life of Clarostat Pots. Maybe someone else will chime in here. I will check on the net though and see if I can find anything on them.

Since yours is not an AB, my gut feeling is, when in doubt change it out. That is what I would personally do, with some 50 years messing with electronics. Wouldn't want a failure on stage, or an important gig.

Mike Wheeler · From: Delaware, Ohio, USA

Roger, if that "cutting out" sound is like what you hear when you have a bad cord, I believe you have a cold solder joint in the pedal. Before I would take the pot apart, I'd desolder, clean, and resolder, all the connections in the pedal. You'll have to desolder the pot anyway to remove it for cleaning, so why not eliminate possible connection problems first.

The insides of these pots do wear and produce some carbon dust that can make them scratchy. This is the situation where turning the pot back and forth clears up the scratchiness for a while. The worst case is that the carbon trace has worn out/through. There's nothing that will repair it in that case.

If you find that the pot is, indeed, the culprit, then follow Dick's procedure and wash it out with a contact cleaner/lubricant.
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Best regards,
Mike

Dick Sexton · From: Greenville, Ohio

Right Mike, I wouldn't take it apart until I'd exhausted the other possibilities. One other thought, if it cuts out only at the off position of the pedal and since it has just had a string/cord changed. The adjustment on the pot might be the problem. I'm not specifically familiar with the Goodrich string pot setup, but on my older EB, I once had it adjusted to run just barely past the carbon track stator of the pot. Produced an audible click like popping the plug out and right back in. Adjusting it to just barely turn the volume off, solved the problem. Note: I could have destroyed the pot, but didn't.

Mike Wheeler · From: Delaware, Ohio, USA

Good point, Dick.

One other thing...there were some Clarostat pots made that were similar to the Allen Bradley pots that we steelers like so much...mil-spec, modified audio taper, etc. They were interchangeable for most practical purposes. The Clarostat taper was serviceable and long-lasting, but just didn't sound quite as good as the A/B's taper. I have used both and wouldn't mind using either one these days...especially since the choices are so limited.
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Best regards,
Mike

Roger Rettig · From: Naples, FL

This Clarostat was fitted by Herby Wallace (as I may have said earlier); I do recall that he'd told me that it was a very acceptable option. It was almost ten years ago now.

I've just looked inside my much-newer (maybe six+ years old) Goodrich and that, too, has a Clarostat.

Pardon my ignorance, but are the ABs no longer available?
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Roger Rettig: Emmons D10, B-bender Teles, Martins, and a Gibson Super 400!
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Kevin Hatton · From: Buffalo, N.Y.

Roger, if you drill a 1/16th hole into the pot and spray tuning spray into it, it will probably last another 10 years. Just don't drill past the housing. Sounds crude but it works. Try it, you have nothing to lose.

Dick Sexton · From: Greenville, Ohio

Roger, it is my understanding that the Allen Bradley pots that I believe were the standard for so long in volume pedals, are no longer being manufactured. They do come available as NOS or Normally Out of Stock parts, occasionally. When they do however, they are usually scarfed up very quickly. The Clarostat used in the pedal you have is a very good pot and I think a 10 year life span is more then acceptable. I used an AB until it gave up the ghost and I could not find one, went to the Dunlop, which I believe is sold by Tom Bradshaw. The Dunlop has given me excellent service, but real or imagined, I like the sound I got from the AB pot. I have been fortunate enough recently, to find a "new in the box" AB pot and have installed it in my main pot pedal. The Dunlop, I'll installed in my back up pedal. It still has lots of life left in it.

Mike Wheeler · From: Delaware, Ohio, USA

Son of a gun, Dick!!! I just did exactly same thing! Found a NOS A/B pot and put it in my favorite pedal and am in heaven to have that old feel back again. And guess which brand pot it was that I replaced?????? Yeah, a Clarostat! Laughing

And my backup pedal has a Dunlop!

What's that they say about great minds following the same track?!?! Laughing

And, yes, neither of them are produced anymore. The Clarostat I referred to looks almost identical to the A/Bs...closed and sealed covers.

Sorry for the drift, guys, couldn't help it.
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Best regards,
Mike

Lynn Oliver · From: Redmond, Washington USA * R.I.P.

NOS = New Old Stock

Mike Wheeler · From: Delaware, Ohio, USA

Good catch, Lynn. Thanks.
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Best regards,
Mike

Dave Mudgett · From: Central Pennsylvania and Gallatin, Tennessee

The old Allen-Bradley 500K pots of yesteryear are definitely not being made any more. John Widgren just sold a batch of NOS AB pots here on the forum a couple of weeks ago, but they're getting hard to find - I picked up a couple. I've been using some Mexican-made Clarostats which have been fine so far. Many people are reporting good results with the Dunlop pots that Tom Bradshaw is selling, haven't tried them yet. But I agree with many others that the old Allen Bradleys are very hard to beat, to my tastes.

As others have said, the sound of a scratchy pot typically sounds like the static caused by contact being made and broken as the wiper moves along the length of the resistive material. But that sound could come from other things such as suggested - I'd want to verify those things are right before tearing an old pot apart. But I agree that once that stuff is ruled out, it makes sense to take the back cover off a scratchy pot and try to clean/lubricate it. Use a good cleaner lubricant like Caig DeOxit D5. I figure - if a pot has given 10 good years of hard service, it was probably made well in the first place and is worth trying to restore. My opinion - the raw 'quality' of lot of mass-produced electronic parts has been on a pretty strong downward slide for quite a while now. I don't throw any old parts away unless I'm sure they're completely dead.

If it cleans up OK, then while the cover is off you can safely drill a small hole in it so you can continue to clean/lubricate it. It won't work forever, but as Kevin says, you have nothing to lose.

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