Remove corrosion off of vintage potentiometers

[Golgoth]

Hello everyone,

I recently acquired a pair of beautiful Neve 3115s.

Unfortunately one of them has quite a lot of corrosion on several pots.
What would be your advice about how to clean it off, or at least prevent it from spreading deeper?

Thank you!
G

 

[Tubetec]

It appears to be caused by a reaction with the rubber used to bind the cable loom .
My advice is remove the rubber thats in contact with the pot bodies , replace it with a few black cable ties .
I'd try scraping away the crud but hold the nozzle of the vaccum cleaner close as you do to pickup all the particles .
Once you have cleaned up the electromould you could apply a small amount of laquer or clear nail varnish to help prevent any further corrosion . Obviously you dont want anything thinners based getting into the pot wafer so be carefull .

 

[Golgoth]

It appears to be caused by a reaction with the rubber used to bind the cable loom .
My advice is remove the rubber thats in contact with the pot bodies , replace it with a few black cable ties .
I'd try scraping away the crud but hold the nozzle of the vaccum cleaner close as you do to pickup all the particles .
Once you have cleaned up the electromould you could apply a small amount of laquer or clear nail varnish to help prevent any further corrosion . Obviously you dont want anything thinners based getting into the pot wafer so be carefull .

Thank you very much, I did not know rubber could react with metal and create corrosion.

I will try and be careful! What would you be scraping with?

 

[Tubetec]

I never saw that kind of reaction before either .
Id use a small blade to scrape away most of the residue , A small rotary wire brush in the dremel might be used after to get you back to bare metal .

 

[Golgoth]

Thanks a lot!

 

[emrr]

For perspective, I mainly deal with gear much older than this and that doesn’t look like a thing that would concern me at all. You can cause larger problems doing something, consider what could go wrong.

 

[Golgoth]

For perspective, I mainly deal with gear much older than this and that doesn’t look like a thing that would concern me at all. You can cause larger problems doing something, consider what could go wrong.

Interesting.. I'm particularly concerned about damaging the wiring and spreading rust dust everywhere in the module..

 

[Ike Zimbel]

I never saw that kind of reaction before either .
Id use a small blade to scrape away most of the residue , A small rotary wire brush in the dremel might be used after to get you back to bare metal .

Here's a thread about the sleeves breaking down and going conductive. I used to think of these as a sign of a careful, quality build (which they are) but now they've turned into one more seemingly innocuous part that can't be trusted

 

[Golgoth]

Here's a thread about the sleeves breaking down and going conductive. I used to think of these as a sign of a careful, quality build (which they are) but now they've turned into one more seemingly innocuous part that can't be trusted

So I should at least remove the sleeves where corrosion is happening? And maybe let what's on the pot be, not to damage anything scraping it off..

 

[Ike Zimbel]

Probably. You could try testing the sleeves with an ohm meter. If you read anything on any of them, they should be removed as they've become conductive.

 

[nielsk]

This type of expando tubing (works opposite of shrink wrap, go figure) is much beloved by British manufactures of the period and much hated by everyone else.
It will exude chemicals that cause all sorts of corrosion, eat circuit traces, and so on...
ANY time you find it, get rid of it ALL. Replace as required with actual shrink wrap or nylon tubing, or a wire tie.
I do agree with EMRR, if the pot is working it may be better to leave it alone, as an attempt to spot repair may do more damage than good. The only way to really repair it is to disassemble to the pot, chemically remove the corrosion, and re-electoplate the metal.

 

[Golgoth]

This type of expando tubing (works opposite of shrink wrap, go figure) is much beloved by British manufactures of the period and much hated by everyone else.
It will exude chemicals that cause all sorts of corrosion, eat circuit traces, and so on...
ANY time you find it, get rid of it ALL. Replace as required with actual shrink wrap or nylon tubing, or a wire tie.
I do agree with EMRR, if the pot is working it may be better to leave it alone, as an attempt to spot repair may do more damage than good. The only way to really repair it is to disassemble to the pot, chemically remove the corrosion, and re-electoplate the metal.

Duly noted! Thanks a lot

 

[Tubetec]

I guess I have to agree with the other two , the corrosion might be unsightly but if its causing no issue with the function of the unit , why worry .
Using heat shrink or tubing means youd need to desolder stuff , again probably not worth the hassle or risk .
get yourself a small packet of black nylon cable ties , clean away the residue of the old rubber material one at a time and replace , being sure not to disturb the layout .
I havent had the pleasure of trying to remove the stubborn black gunk , you could try a cotton bud moistened with lighter fluid , Ive also found tea tree oil useful for disolving grime .

 

[Golgoth]

I guess I have to agree with the other two , the corrosion might be unsightly but if its causing no issue with the function of the unit , why worry .
Using heat shrink or tubing means youd need to desolder stuff , again probably not worth the hassle or risk .
get yourself a small packet of black nylon cable ties , clean away the residue of the old rubber material one at a time and replace , being sure not to disturb the layout .
I havent had the pleasure of trying to remove the stubborn black gunk , you could try a cotton bud moistened with lighter fluid , Ive also found tea tree oil useful for disolving grime .

I'm scared of the rust spreading deeper into the pot, which would be a nightmare to replace.

I believe that if I remove the rubber shrink wrapper pieces causing the corrosion the process will stop and the situation won't worsen!

I will replace the pieces with black ties as advised

 

[emrr]

I'm scared of the rust spreading deeper into the pot, which would be a nightmare to replace.

It really doesn't look bad at all. You might have a heart attack if you saw most of what I work on, this looks better than most. I see a lot of fully red/brown crumbly rust on parts like this, and if you pull them the unexposed part is nearly always new looking. Last year I helped restore 20 RCA tube preamps from the early 1930's that had been in a barn for at least 2 decades, the rust was so heavy we had to lightly wire brush and wash all possible parts of the chassis, and after that you had to wash your hands every time you touched one. All 20 came back and work fine.

 

[Golgoth]

It really doesn't look bad at all. You might have a heart attack if you saw most of what I work on, this looks better than most. I see a lot of fully red/brown crumbly rust on parts like this, and if you pull them the unexposed part is nearly always new looking. Last year I helped restore 20 RCA tube preamps from the early 1930's that had been in a barn for at least 2 decades, the rust was so heavy we had to lightly wire brush and wash all possible parts of the chassis, and after that you had to wash your hands every time you touched one. All 20 came back and work fine.

That's incredible! Thanks for sharing

 

[swpaskett]

It's what's inside the pot that matters. I wouldn't worry about it until you start hearing scratchy pots, then you are in for a fun ride. The only truly effective way I have found to clean pots is to pop the back off and get in there with a Q-tip, no tun at all.
If that rubber stuff really is a corrosive, I agree with the others, get rid of it. When I care about something I always fall back on the techniques and materials we used for aerospace work. You can get lacing tape, basically wax coated flat nylon string that does a beautiful job on wire looms. It is much more compact that wire ties, which incidentally were not allowed for aerospace gear because they break and can go flying arund and you never know where they might end up.