scratchy volume pot

[messylife]

i recently bought an older power amplifier (alesis ra100) for spare parts since it was advertised with a broken left input, but upon testing , i fould that all inputs and outputs work fine - the casing has apparent trama from being dropped (on its left side) but everything else is perfect and intact.

the only problem that i found was a scratchy volume pot on the left side only when turing the volume up or down, but when static, the signal is clean. I tried spraying the pot out with an electronics cleaner to see if that would help but didn't have any effect.

does anyone else have any solutions to get rid of the scratchiness with out replacing the original pot?

thanks

 

[Jan Dupont]

Hi,
Try using WD40 from your local hardware store...
I got this advise from Rob Flain from QUAD in England several years ago, and all the npots I have tried it on (even pots in 20 years old QUAD's hasn't given a single "scratch" after one cure 3 years ago....

 

[messylife]

thanks ACD - i will give it a try!

 

[djQUAN]

I have tried the WD40 trick but mine gets the scratchy thing back in about a few months. is there a special way to do it?

 

[Jan Dupont]

I use it as I would use normal Contact Spray, so no special trick there........ Try using Contact Spray first, and then add WD40.

 

[phase_accurate]

Even though I have used WD40 by myself for that purpose there are people saying that it does more bad than good.

Another thing to watch out for:
Pots can not only scratch when dirty, the same thing can also happen when DC current is flowing via the wiper. This is often caused by either DC-coupled circuits with too much offset voltage or leaking (electrolytic-) coupling caps.

Regards

Charles

 

[messylife]

in that case wouldn't the scratchyness be found on both channel volumes being they are hooked up to the same transformer? I am pretty sure I have isolated the problem to the pot itself.

i've already tried to use some contact cleaner but that ddin't seem to work completely - it helped alittle though. so is wd40 a go or no? i don't want to kill the thing, i don't know if i can a matching pot being they are out of production now and i couldn't find any labeling on it

i suppose i could always just write to alesis and see if they could hook me up if i can't get the scratchyness, even though it desn't affect play when i am not activley changing the volume

thanks for the help and replies!

 

[Jan Dupont]

As earlier mentioned, I have used WD40 on >20 year old special made QUAD pots with perfect results...
I do not belives in miracles, however this saved my butt in case

 

[Paradise_Ice]

GT 85 is better than WD 40 in this case,
WD40 is a little thinner and the particals do not get swipped out the way that well, GT 85 is a thicker formula and will really scoop the dirt in your pot side ways! I promise,

 

[djQUAN]

what about putting some sewing machine oil after spraying with WD40?

 

[ALBQ]

Refrain from anything that leaves residue

All (IMHO),
As much as I love WD40, for cleaning pots and switches, it is advisable to refrain from using anything that leaves behind a residue, film or oil. The scratching sound you are hearing is caused by a poor connection, sometimes intermitted connection, between the contacts and/or wiper of the pot and conductive surface (in case of carbon) or winding (in case wire wound). Although WD40, etc… may temporarily solve your problem, it will leave behind oils that will accelerate the "getting dirty" degradation process. So, a high quality, non-residue, non-conductive contact cleaner is always preferable. A good product that works wonders is CRC Lectra-Motive. It can be bought at your local auto parts store for about $5 can. It degreases (more often than not the root cause of noise on older equipment - people spraying them w/WD40), is non-conductive, does not leave a residue and is generally safe for use on most plastics.
Cheers -ALBQ

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