Weird squeal when touching the tone knob

Piing

Axe-Master
Guitar: Schecter Nick Johnston USA with Seymour Duncan Antiquity Texas Hot. Metallic knobs

With medium or high gain settings, touching the tone knob causes a high-pitch noise, similar to the one that happens when you place the pickups close to speakers without magnetic shielding. With clean settings there is a low hum when touching that knob.

The noise doesn't happen if I touch the tone knob while touching the strings, the bridge or the volume knob at the same time

I still haven't opened the pickguard (I am waiting for these NYXL to worn out a bit more) but I have measured a resistance of 250 ohms from the tone pot to any other metallic part of the guitar.

I expect to see some issue with the ground connection, but I don't know how to explain the "oscillation" that causes the squeal. You need an RC network for that. Perhaps the combination of these 250 ohms with the tone capacitor? Or maybe my body is a squeal tone generator :D

Have you ever experienced a similar issue?
 
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Reply to myself:

The tone pot was not directly wired to the main ground point at the volume pot but connected through the metal film and the pot case, which are poor conductors. That was the cause of the 251 Ohm resistance between both points

After wiring them directly, not only the squeal is totally gone, also the noise has been dramatically reduced.

I'm not surprised that the previous owner sold it. Lucky for me, because this guitar is a keeper :sunglasses:


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