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The guy who took the pics tried something called "liquid wire", but foudn it's not so conductive - the burned segment should be 25 ohms, but he ended up with a few hundred ohms. The total is supposed to be 100 ohms. I suspect this low resistance and the high currents involved (compared to a video or audio signal) are pushing the carbon pot technology beyond its limits. I suspect high contact resistance could develop and then there would be local heating. Don't know why they didn't use wirewound pots for this function. The circuit I came up with using two pots has a wirewound 25 ohm in it, mainly because that's what I could find. There is no problem with coarseness of adjustment for this application.
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