Buzz/Loud Hum isolation

[ack1961]

I have a P/J (V/V/T) that was acting funny - severe volume drop when both pickups on full and the pickups were leftover crap anyway...to make a long story short, I just had a P/J set hand wound for me and went to drop them in last night.

I'm following the P/J diagram below.

After I solder everything up, I hear a very loud hum (almost a buzzing) that only goes away if I touch any of the 3 knobs. Touching the strings or bridge doesn't stop the buzzing. It happens no matter which pickup is rolled on or off. It doesn't sound like bad ground hum, it's way more distinct than that.

I opened it up and checked all the solder joints. I noticed that the Capacitor leg that was supposed to be grounded to the back of the Tone pot was off, so I re-soldered it. Even after re-soldering, the buzzing continues, but I can get the buzzing to go away if I move the capacitor around a bit. Thinking it was broken, I replaced the cap (.47uF) with a new one, but the problem persists. If I touch the lug that the capacitor is soldered to, I can hear a distinct change, and sometimes a popping noise.

I thought the Tone pot itself (250k) is causing the issue, so I replaced it...problem continues.

I then took the Tone pot completely out of the picture (V/V only) and wired directly to the output jack. Same issue.
I can still get the buzzing to change (not go away entirely) if I touch the lugs of the output jack.

I'm thinking about changing the output jack - am I just chasing my tail here, or is there a better way to isolate the cause of the buzzing?



Any useful advice would be more than welcomed.  Thanks.
Steve

[patman]

did you check the ground wire under the bridge?

[ack1961]

did you check the ground wire under the bridge?

Yup. I disconnected it and tried it - made no difference whatsoever.
-------
Let me be more specific - I disconnected the bridge ground at the Tone pot and it made no difference.
I guess there's a possibility that the ground wire could be dorked under the bridge, but I thought that if it was the bridge ground, I would hear a difference when I touched the bridge.

[dadagoboi]

Who wound the pickups?

A few years ago I had an Antiquity Jazz set from Seymour Duncan that did the same thing.  After about 5 hours of trying all you have and more I called them, they IMMEDIATELY told me that I probably had a set that was mismatched for polarity.  Yep, switched white and black on one pup at the pot and problem solved.  I was so happy I didn't get pissed off...for a while.

Give it a shot.

[Lightyear]

I had the same polarity issue on on set of SD pickups as well - easy enough to try.

Do you have a meter?  I would verify ground though out the entire circuit.  Barring that I would isolate the pickups from the other components and test them directly to the jack - I have a cheap set of jumpers with alligators clips that works great for these kinds of things.

[Highlander]

+1

Prove the pups (individually) before you go any further...

[dadagoboi]

Vol cancellation and hum indicate the problem, no need for further testing IMO.  Switching the wires takes less than 2 minutes with a decent soldering iron.

[Basvarken]

I guess there's a possibility that the ground wire could be dorked under the bridge,

yes that's what I thought.
Try a temporary lead between pot and bridge just to make sure.

[ack1961]

did you check the ground wire under the bridge?

Posted by: Basvarken
Quote from: ack1961 on November 24, 2012, 08:07:37 AM
I guess there's a possibility that the ground wire could be dorked under the bridge,

yes that's what I thought.
Try a temporary lead between pot and bridge just to make sure.

---------------------------------
Bingo! thanks to all for the replies.
The bridge ground wire was split somewhere in the body.
I replaced it and all is perfect.
I did a lot of needless soldering and component swapping but that's what you get...
I needed the practice - my soldering is pretty ugly.

Just to answer a few questions, I had Jammer Guitar Company (JGC) in Philly wire me a P/J set.
I actually saw his ad on CL and gave him a call.
I spoke to Mike on the phone and he asked a lot of questions about what I was looking for out the pickups.  
He's the Owner/Sole employee of Jammer - I thought I'd give it a shot.
Quick turnaround time - he started winding as soon as I PayPal'd the money.

I wanted a passive set with deep lows and thump out of the P and some bite (but not too nasally) out of the J.
I also wanted something pretty noiseless and mudless.  
After fixing the ground issue, they are exactly what I was looking for.

Thanks again guys!
Steve

[dadagoboi]

Cool!