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How to remove corrosion from plate and antenna variable caps


Jun 17, 2008
I have a tube amp that I am refurbing. This box was in a shed for many years, and there was corrosion everywhere. Not rust, just the white corrosion that metal parts get when they sit for a while. I disassembled it completely, and was able to clean everything except the chassis (some rust) and the plate/load variable caps. I bead blasted the chassis back to bare metal, and had it cad plated at a local shop. But the caps have me stumped. Only the vanes on the caps are corroded. I tried using my ultrasonic cleaner with some solvent, but it only removed about half of the corrosion. The plater said he could put them in his cleaning vat, but he thought the cleaner would damage the aluminum and the nylon bearings. I'm at a loss. Any suggestions anyone ???

- 399

Something I have heard about on an AM ham forum is putting the capacitors in a pot with crushed tomatoes and using a low heat. Make sure the plates are completely covered. Not sure how long it takes but apparently the low acidity of the tomatoes will make the plates look like new. I never heard of it before but several old timers running some pretty heavy iron swear by it. Just wash thoroughly after and lube the shaft bearings.

I decided to go with Wavrider's suggestion of white vinegar and water. I had a couple of smaller variable caps in my junk box, so I soaked them in the mixture, and they came out clean as could be. I need to buy a more vinegar because the linear's caps are much bigger. I'll post before and after pics when I'm done cleaning them.


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