I just completed a custom build guitar with an L610 in the neck and an L-90 in the bridge position. The L-610 is quiet as a church mouse. The L-90 however, has what I assume is ground noise.
With no hands on the guitar, if I touch the metal pickup ring of the L-90 I get ground noise. If I complete the loop by touching the strings with the other hand the noise goes away. This same procedure performed with the L-610 is completely silent.
I shielded all cavities with Stewmac conductive shielding paint. The exception is the plastic control cover. I lined the backside of that cover with copper tape, so the control cavity is a combination of shield paint and copper tape. I was meticulous with the shielding paint including ground screws with individual wires in each pickup cavity and the control cavity. plus a bridge ground wire. Each of these cavity screw/wire ground points are painted over with shielding paint.
This left me with many ground wires. 4 from cavity/bridge ground wires. 4 total blue/white pickup wires, 1 from the switch, 1 from the back of each pot and 1 from the input jack. Total of 12 wires to be grounded. I could not see trying to glob all of these wires with solder onto the back of a pot. So I chose a route which may be a bad. I soldered all of these ground wires together in 3 groups of 5. The 5th wire in each bundle is a jumper wire. Then I soldered the 3 ground jumper wires together. All solder connections are well insulated with shrink wrapped. The one point that makes me think my method is acceptable is that the L-610 is perfectly quiet. I would think if my method was flawed, both pickups would exhibit similar noise issues.
Other than my ground wire bundling method, I followed the attached diagram exactly. It was reviewed and approved by Becky.
I would appreciate any suggestions?????
Link to original wiring diagram here
Added diagram showing ground wire bundling scheme here
Photo of finished guitar, if interested here
