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Scratchy Pots

#2
I've found that spraying a little electrical contact cleaner into the pot can eliminate the scratchy sound. I buy it at the local electronics store. I use the kind without the lubricant in it.

This may or not be a good approach. It works for me, but maybe some of our more technically skilled guys can confirm.
 
#4
Scratchy pots mean that when you turn the pot, you get this scratchy sound that can be heard through the amplifier. It's not really a huge issue, like it'll ruin your bass. It can get annoying, though. Its usually caused from dust getting in there. Should be a quick fix, although I've never cleaned any of mine.
 
#6
kful said:
I'd just replace the pots. It's not too hard, and really cheap if you do it yourself.
Click to expand...

When I suggested the contact cleaner, I made two assumptions that may not have been valid. If I was wrong on these, I apologize.

First, I assumed that since the OP didn't know what a scratchy pot was, that he wasn't someone who normally worked on their own guitars, and wouldn't feel comfortable wiring and soldering in new pots. Depending on the pots you need, it could be expensive to have someone do it for you, 'expensive' being a relative term.

Second, I assumed that the OP might want to keep the T-40 as close to original as possible. They are collectibles, and even though new pots don't hurt like other mods or repairs, it is always a plus to have the original wiring harness in place.

If these assumptions are correct, I'm not sure the DIY route is the best way to go.
 
#7
FWIW, inside the pot body, contamination of the plastic conductive material and or the wiper/wiper to center lug are the prime reasons for erratic operation of "Pots". Most electrical cleaners will help in the short term or better. Though some ( many ) are based on various chemical compositions around White Spirit.

Better choice for initial clean can be CRC CO cleaner ( code 2016 ) though this strips out any lubrication as well as the contaminates. Follow through with CRC 2-26 ( code 2005 ) to restore the lubrication, though this is a very light lubrication and will disipate quickly, say 3-10 days.
Many of the lesser than cleaners based on "clean and lubricate" are at odds with the two different requirements ie to clean and then lubricate. WD40 is a dust attracter and can damage plastic, fine for rusty metal, not cleaning delicate electronics. Replacing pots is a last resort, easy things first, with good quality chemicals should give the desired repair.

BTW, can never understand why pots are "boiled" in solder by soldering the metal ( often steel with plated or passivation process ). What do the operators of this technique think is happening to the plastic and lubrication inside the pot??? Fabricate a single point inside the electrical compartment for attaching or soldering the return(s) ( earth or ground if you must ) this will ensure less chance of return loops and provide a purpose made facility to accept connections both mechanical and electrical. HTH and regards from John
 
#8
Eight_Stringer said:
FWIW, inside the pot body, contamination of the plastic conductive material and or the wiper/wiper to center lug are the prime reasons for erratic operation of "Pots". Most electrical cleaners will help in the short term or better. Though some ( many ) are based on various chemical compositions around White Spirit.

Better choice for initial clean can be CRC CO cleaner ( code 2016 ) though this strips out any lubrication as well as the contaminates. Follow through with CRC 2-26 ( code 2005 ) to restore the lubrication, though this is a very light lubrication and will disipate quickly, say 3-10 days.
Many of the lesser than cleaners based on "clean and lubricate" are at odds with the two different requirements ie to clean and then lubricate. WD40 is a dust attracter and can damage plastic, fine for rusty metal, not cleaning delicate electronics. Replacing pots is a last resort, easy things first, with good quality chemicals should give the desired repair.

BTW, can never understand why pots are "boiled" in solder by soldering the metal ( often steel with plated or passivation process ). What do the operators of this technique think is happening to the plastic and lubrication inside the pot??? Fabricate a single point inside the electrical compartment for attaching or soldering the return(s) ( earth or ground if you must ) this will ensure less chance of return loops and provide a purpose made facility to accept connections both mechanical and electrical. HTH and regards from John
Click to expand...

Even though I am not the OP, I appreciated this post immensely. I assume we can get the cleaner and lubricant you mention at an electronics store? Something like Radio Shack? Are those codes universally known?

I was intrigued by your comments on pots and soldering. Could you possibly expand on your comments there? The message I'm getting is that we shouldn't solder anything to the pot, except for the lugs, despite wiring diagrams indicating otherwise.

I have always wondered about this, given how hot the pots get sometime, but I just figured the pickup manufacturers knew how they should be installed. I sense that some of us who like to do our own work (but are not knowledgeable in electonics) are on the verge of learning some valuable lessons. Anything you can tell us in this regard would be truly appreciated.
 
#9
If you know how to solder, you won't damage the pots by soldering to them. Scratchy pots in an otherwise factory original bass did not get that way from the solder on the back of them.

Invalid Link Removed (Don't worry no working pots were destroyed in the making of this photoset)

As you can see, the back isn't touching anything inside directly. The only ones you have to worry about are the ones with a screw or nut on the back in the center. But you won't run into those on any bass I've seen or know of, and they usually have a tab for the case ground anyway. The pot I took apart for that photoset has a ground lug for soldering, its on the treaded body.

Grounding your cases is important in most basses, its less important if you have a well sheilded cavity as more often than not your pots are touching the cavity sheild and are grounded that way...
 

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