Ground is a circuit connection
In the supported passive guitar circuit, ground is the reference and return network for the signal. Volume lug 1, the designated control grounds and jack sleeve belong to that network. Jack TIP carries the output signal. A casing used as a solder point is not the pot’s wiper.
A wire can look as though it reaches a casing without making a reliable electrical connection. Conversely, a different physical route can be electrically equivalent. Identify the intended nodes and verify continuity rather than relying on the appearance of the harness.
Shielding and signal return have different roles
A shield intercepts unwanted electric-field coupling and is connected as specified for the instrument. Pickup shielding, cavity shielding and the signal return can meet at ground, but their purposes should still be identified. A bare shield is not automatically an available coil conductor.
Cavity shielding does not replace the pickup’s required electrical return. It also does not guarantee elimination of every type of hum: magnetic interference and the pickup’s construction matter. Avoid describing shielding material as a universal cure without identifying the noise mechanism.
Start outside the cavity
Use a known-good cable and a consistent input before modifying the instrument. Check whether the problem follows one pickup selection, all selections or movement of the cable. A fault common to all positions can be in the jack or shared output path rather than inside every pickup channel.
Changes when touching strings can provide a clue about shielding and grounding, but they are not a complete diagnostic test. Record what changes and check the specified bridge/string ground where the circuit requires it. Some active systems have different requirements; follow their manufacturer’s instructions.
Identify sleeve and TIP directly
Use the jack documentation and, where useful, an unconnected inserted plug to check which solder lug reaches TIP and which reaches sleeve. Apparent lug position is not a substitute for contact identity. A reversed or loose jack connection can create symptoms that look like a much larger wiring problem.
Inspect for conductive parts touching the jack signal lug, stressed leads and rotation of the jack body. Secure mounting and adequate clearance matter. Work with the instrument disconnected; resistance readings made through attached equipment can be misleading.
Look for unintended signal-to-ground paths
Check volume input lug 3 and wiper/output lug 2 for solder bridges to the casing or grounded lug 1. Inspect capacitor leads and selector tabs near grounded metal. A tone-loading branch belongs at its configured signal node, through the tone network toward ground; grounding the signal directly is a different connection.
Do not assume that every low resistance reading proves a short. Pickups and pot tracks provide legitimate paths, and connected branches affect a meter reading. Isolate a suspect section when needed and compare it with the intended connection list.
Change one thing after identifying the fault
Establish the signal path and return path, inspect joints and then test the specific connection suggested by the symptom. Replacing parts without isolating the fault can add variables and leave the original problem in place. Keep a record of the exact configuration and terminal identities.
The Wiring Diagram Generator is a connection reference; it cannot inspect a physical joint or diagnose environmental interference. Never defeat equipment safety grounding to test a guitar noise theory. If a symptom points to external powered equipment, address that equipment through appropriate qualified service.