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Hi, i recently finished a les paul style solidbody with seymour duncan pickups. But i have a hi pitch feedback problem with high volumes and hi gain. The cavities are well isolated with copper foil tape, and the wiring seems to be ok, it's not the first time i got the same problem, but other times i think it was due a not so top quality pickups. Maybe the pots? Some tip to fix it??

Thank you!!

Is it squealing?

Cheapy pickups might need to be potted in wax.

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"Act your age, not your shoe size" - Prince

He said he is using Seymour Duncan pickups so I would think maybe there is another issue then potting. The issue I see many times is pickup height. People think that it is alright having the pickup height as close to the strings as possible. Well it's not. Backing the height down helps with feedback issues. With high gain and high volume setups and pickups to close you will have issues. Now if this fail double check all the wiring from posts to jack output. Could be a short somewhere but I say start with adjusting the pickups first. Both of them.....Mike

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wah
Wah-wah-wah-wah
Wah

Also, just for the heck of it, make sure you're not setting right up next to a cranked high powered amp. Everything squeals when you do that.
In fact, if you've ever watched a pro soundcheck you'll often see either the sound man or the artist crank their amp, then move around the stage, looking for the places on stage that they cannot go because of feedback issues. They'll sometimes even mark those areas with tape so as to avoid them.
If you're trying to hear what your guitar sounds like at high volume, make sure you're a good distance away, and that it's not pointed at the speaker(s). FWIW.

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Mike

The only thing nescessary for evil to thrive is for good men to do nothing.

Well, i use alpha pots, some measurement say me than it's a bit avove 500k (515 or so) can be this be a problem? When roll off volume pot, just a bit the feedback seems to end, everything else seems to be ok: no shorts, everything well isolated and chequed

Nope.

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wah
Wah-wah-wah-wah
Wah

If the pickups are properly wax potted then the squeal has to be a mechanical rattle somewhere on the guitar. Something is loose so that it vibrates at a high frequency. It could be in the pickup mounting, or any piece of ferrous material close to the pickup, strings or bridge. Something on the guitar is loose. Could be a mounting spring which is not compressed and can rattle.The way I go about finding it is by plugging into an amp at moderate volumes and tapping and pounding on the guitar with my fist, knuckles, a pencil (eraser end) until I can get a rattle sound. Sometimes you can hear it better with no amp in a quiet room. Go over the whole guitar and look for anything that might rattle.