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Tone Knob Squeal


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I'm a self confessed electonic idiot. I can build a guitar, follow a diagram, but when it comes to trouble shooting I'm lost. This is something I'm working on and learning very slowly.

I've got a lefty guitar here. I've wired it up with my usual diagram. I've swapped the top/bottom tabs on the pots so they turn the correct way for a lefty.

The problem is the tone knob. Turned to zero the sound is ok. Turn it up a tad and theres an ear piercing high frequency squeal.

- The function of all the pickups, selector switch, coil split, volume and tone all work as they should.

- There is lots of earth hum wheres usually this circuit is silent

- Touching the bridge/knobs etc the earth hum gets louder

- Moving the pickup selector has no difference on the hum/squeal, only the tone knob

I've gone and resouldered all the earths to make sure they're right. The bridge is earthed. I've replaced the cap in case that was an issue.

I'm lost - don't know what to check or look for. I've never had problems with this circuit before. I always wire and it works first time!

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It works, but all the 'earth' circuit becomes a big antena for noise. However, I doubt that's the cause of this other squeel. Unless the pickup needs repotting?!?!

Grab a set of alligator clip leads, and start at the pickup. Connect the leads to the guitar lead into the amp. Slowly reclip the leads following the signal path and you'll find where the problem originates from. Use a common earth (eg: jack)

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First of all - thanks to Perry.

The jack wires were back to front.

Also found one of the connectors on my tone pot was very loose - so loose I'm amazed I didnt notice whilst soldering.

All good now - I was very pissed off about this as the customer is hanging to see his "custom" guitar and I've been stalling!

Thanks again. I really need to learn electronics but with so much else to learn it on towards the end of my list!

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