Help with electronics.

[Urizen367]

I picked up a Global LP Jr copy at a yard sale that gave me the feeling some people get when a stray kitten comes up to them.  "I'll be your parent.  I'll get you right as rain."  This is also my first real re-build.  Usually I just stick to switching out pickups or doing basic set ups. 

 

So I have done a lot of work with it.  It originally came with a P90 (I was unable to test the guitar because at time of purchase, it did not have a tailpiece, by extension no strings).  I pulled the P90 and installed a Duncan design HB-103b.  Get work on it taken care of, get strings on, plug it in for a quick test.  There was a lot of hum and no sound when I plucked the strings.  To give an idea of the hum.  It would be like if you had a cable that wasn't in a guitar but is in an active amp, and you touch the tip.  That sound, but four times louder.  So I figure, it's probably the pots (this guitar has been severely neglected, it could have been anything.  So I switched out the pots.  Still get the same noise, but now I have a signal when I slide my fingers up and down the fret board.  My next option is going to be replacing the output jack and wires.  If the noise persists, I'll check the ground.  But I was wondering what other issues may be causing this. 

 

A little idea about the pick-up and position.  The original P90 was flatmounted onto the body.  Just, slapped right on top of the sucker.  I flatmounted the humbucker, which sits a little higher in the same location.  I still think I would be getting some kind of action from the strings instead of loud hum or signal upon sliding my finger up and down the neck.

 

If it's a lost cause, I'm not going to be super upset about it not working, my main loss was in parts cost that I can put onto another guitar.

[drewski]

It sounds like you have an output signal wire shorting to ground, hence the loud buzz that sounds like touching(shorting) the tip of an open guitar cable.  Check the current wiring against a schematic that has the same setup, Seymour Duncan has a bunch of these.  Could be the output jack shorting itself out, or could be a wire that has been damaged and exposed and causing a short.

[Urizen367]

Followed SD's wiring diagram on this one.  I'll be changing the output jack later.  If it's a ground issue, that's going to be a bit of a pickle, as it's grounded to the tailpiece studmounts, which are very snuggly embedded into the guitar.

[curtisa]

7 hours ago, Urizen367 said:

But I was wondering what other issues may be causing this. 

Broken ground between output jack and rest of guitar circuitry, or missing ground from bridge studs would be my guess. The hum and buzz from a missing ground on the bridge studs would clear up if you rolled the volume pot on the guitar to zero. A missing ground from the output jack would make lots of noise whether you had the volume up or down.

 

6 hours ago, drewski said:

 

It sounds like you have an output signal wire shorting to ground, hence the loud buzz that sounds like touching(shorting) the tip of an open guitar cable.

 

Unlikely. Shorting the output signal to ground will result in a complete absence of signal.

[curtisa]

Moved to the Tech Area -> Electronics Chat section for better housekeeping.