[Boatanchors] Cleaning Cigarette-Stained Plastic Knobs

[w0ng at comcast.net]

Hello all - I'm in the process of restoring a National NC-303 receiver. The front panel plastic knobs are uniformly stained a light brown for about 3/4 of their outside surface. I'm presuming it's from cigatette smoke over many years.The remaining 1/4 portion of each plastic knob is still the original grey color. I've tried vinegar, ammonia, plastic polish, scrubbing bubbles bathroom cleaner, kaboom kitchen cleaner to no avail. I'm hesitant about putting them thru the dishwasher as it will probably remove the lettering on the center disk of each knob. Can anything you all know of remove the light brown stains on the plastic knobs? Any help appreciated. Tnx, Bill
-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.qth.net/pipermail/boatanchors/attachments/20090201/12b9af1b/attachment.html