Static sound when turning volume knob

Looking for the cause of "static" type of sound in the speakers when I turn the volume knob on my preamp? It is a passive preamp, so I figure it must be the potentiometer itself. How would I clean the contacts with the resistors? It is a TKD stepped potentiometer.


It's not the resistors that need cleaning but the contancts of the actual stepped attenuator. I would suggest that you carefully spray the contacts with the cleaning solvent of your choice. Once thoroughly saturated, rotate the control through each step several times. Once that is done, continue rotating the control while spraying cleaner. This allows the cleaner to penetrate the crud, rotating the control helps to break up the crud and then flushing it while rotating rinses the crud away.

Too many people use cleaning solvent sparingly. All that this accomplishes is that they loosen up the "gunk" but don't fully remove it. Over time, the "gunk" migrates back into the contact area and gives you problems all over again. You not only have to clean the gunk off the contacts, but you have to fully remove it from the area. Use an old hand towel or several layers of paper towels under the device to catch all of the run-off. Sean
I had the same problem with my pre-amp volume knob, but it is not stepped and it is a sealed unit, so I could not clean it. I just "exercised" it by turning it back and forth and it alleviated the problem. But Sean is right -- if I could clean it, I would.
Ncarv: All "sealed" controls can basically be cleaned, but it may not be easy. The method that you described basically helps to loosen up the gunk via stimulating the contacts vigorously, but the gunk is never fully removed. As such, you can expect more problems further down the road. On top of that, working the control back and forth in rapid motion may also help to imbed the foreign particles into the conductive path, making them harder to remove even with a thorough cleaning. As such, it might be a "quick fix" but you really should deal with this in the proper fashion for best results. Doing things the right way is typically cheaper than "getting by for now" over and over again.

Rather than respond to the emails that i received ( and the others that i'm probably missing due to continued computer problems ), i'll respond here for sake of simplicity. While i could recommend specific brands that i've found to work very well, even these can create other problems in specific situations. As such, i'll fall back on what i've found to be the most "universal" cleaning agent that i've found and is easily available through local means. This stuff works without having any major problems associated with it i.e. plastic melting, contacts seizing up, etc...

The product that i'm talking about is Radio Shack Tuner Control Cleaner & Lubricant. While i don't think that this does the best / most thorough job, it has been the safest to use out of any of the products that i've tried. If you follow the directions above, it should solve all but the most difficult problems. On top of that, this cleaner contains a lubricant, which helps plate the contact path. This not only helps keep it from further corrosion and pitting, but it can reduce wear too. As mentioned though, the key is to not only break the gunk up by vigorous rotation of the control, but to thoroughly flush it out with copious amounts of cleaning solution. Think of it like taking a shower. What good is it to use soap to loosen up dirt without removing the dirt from the area all together ??? It just gets stickier and feels even worse.

I've had several people contact me about this recently. They had purchased some cleaner, sprayed it into the offending controls and the problem went away. A couple of weeks later, they ran into the same problem. After they read a post that i had made about this over at AA, they followed the same basic directions that i posted here. This time, they not only sprayed the control internally, but worked it through the entire range of motion ( VERY important ) and then flushed it out thoroughly while still moving the control.

Upon flushing the control, all kinds of "black crud" came flowing out of it. This scared them to say the least and they thought that they had broken the control. They were afraid to use the device, so they emailed me. I simply explained that all of the dark liquid that they saw was a combination of foreign material that had found its' way into the pot and carbon from the trace inside the pot. So long as they kept streaming cleaner into the control until it was flowing out clean again, everything should be fine. They fired up their units and had no further problems. Just don't forget to place a towel under the unit to catch all of the run-off.

When large quantities of "black crud" come flowing out of the control, that is a sign that the control is very worn and may need replacement soon. Depending on how much you use this device, it may last for many more months of daily use or it might give out not that far down the road. While thoroughly flushing it out and using a lubricant can definitely extend its' useful life, it can't repair the damage that was already done. If the control starts acting up after a thorough cleaning, chances are, it needs to be replaced.

As a side note, high purity alcohol can also be used for this purpose, but the problem is being able to inject it into the control at a high enough flow rate to thoroughly dislodge the dirt and flush it out. On top of that, the alchohol removes any type of lubrication that the control may have already possessed. The end result is increased potential for pitting and / or dragging of the control in the not so distant future, possibly speeding up the need for replacement.

Hope this helps and clarifies what i was talking about. If you've got further questions, please post them here so that others can benefit from the answers. Sean
Thanks for the tip, Sean. I'll try it.