Odd sound problem: No output from pickups when string is plucked

[6StringSling]

I've wiring up a double neck. All the solder joints are solid. The 6-string pickups work fine in all positions - 6-string neck only and 6/12-string necks both active in the neck, neck/bridge and bridge positions.

 

The 12-string pickups have no audible output when I pluck a string but definitely have output if I tap a pole piece with an allen wrench.

 

There is also a hum. I'm don't think it's a grounding issue as I've wired a ground from both neck's stop tail posts to the ground tab of the neck selector switch.

 

Any ideas as to the culprit?

[mrbrown49]

Are the leads reversed?

[6StringSling]

 

Are the leads reversed?

 

The leads to what? The pickups? If so, how could they be reversed?

[mrbrown49]

 

The leads to what? The pickups? If so, how could they be reversed?

 

 

How many conductors are there on each pickup?

 

Follow the whole path from pickup to switch and to jack and make sure the hot pickup lead makes it too the hot jack tab, and same with the cold.

[SomeoneYouKnew]

The 12-string pickups have no audible output when I pluck a string but definitely have output if I tap a pole piece with an allen wrench.

How much output when the 12-string pole pieces are tapped with an allen wrench compared to when the 6-string pole pieces are tapped? If they're similar (don't have to be exactly the same), then it would seem the problem is likely the 12-string pickups are miles too far away from the strings, or the strings are made of the wrong alloys.

[6StringSling]

Thanks for the help. I'll spare you the list of bizarreness that I experienced trying to figure this out. What I ended up doing was removing the ground wires from all the pots and resoldering them. I had one wire between each neck's volume & tone pots and then one wire between the two volume pots. I moved that one to be between the two tone pots and it seems to be working fine now.

[mrbrown49]

Thanks for the help. I'll spare you the list of bizarreness that I experienced trying to figure this out. What I ended up doing was removing the ground wires from all the pots and resoldering them. I had one wire between each neck's volume & tone pots and then one wire between the two volume pots. I moved that one to be between the two tone pots and it seems to be working fine now.

 

Interesting. Sounds like you had a ground that wasn't actually making it to circuit ground. Glad you got it resolved.

[maveric_manic]

There is a debate if you should wire your pots on the "back" side of the pots. First let me say that I am a Guitar tech and a Electronic Engineer so I will only state the facts based on my training. If you understand ground loops of a circuit you have a connection to ground just putting the pots through the hole for the pot assuming the cavity is sprayed with conductive paint. When you wire the back of the pots you have another ground circuit and when you solder this to the sleeve of your output jack you have now connected (2) different grounds together. The same with all the wiring like the Tone pots. If you have grounds that are scattered about these are ground loops. ALL grounds should be connected to (1) point near the pickup grounds. This is true of amps also and will give you a less noisy signal. Shielding with copper foil does wonders even with P-90 pickups. The bad connection was probably a cold solder joint because heating the back of a pot requires a lot of heat and your wiper contact will sound scratchy with to much heat. A Pot is easily damaged with to much heat. Never solder to the back of pots use a ground terminal that can be screwed in as a collector of all ground wires then run a wire to the ground of your output jack. This include the grounds on Pots. And yes I have had trouble with ground loops and it is a common problem. Hope this helps someone that is trying to get rid of the noise in the cavity.

[maveric_manic]

Try using an ohm meter because this will tell you the resistance of the coil. While measuring it wiggle ALL wires to see if it is a good connection. You really do not know if a connection is good without the proper test equipment. You could by a cheap Analog meter for less than $20. The coil could be tested out of the circuit and by process of elimination you will find the problem.