Symptoms of a bad pickup?

[Dennis Detweiler]

My steel student recently bought a Zum Encore. He's suddenly getting a bad hum. I removed the input plug and resoldered the wires. Also checked the plug for cracks. Couldn't find anything wrong. I'm thinking a short in the pickup? There's not much more to it other than the pickup wire leads. I moved them around while it was humming and found no change.

[Donny Hinson]

A short in the pickup usually means no sound at all. Whereas, an open pickup will usually sound thin and weak.
Has he changed anything in his sound chain or surroundings? Sometimes adding an AC powered pedal or accessory can cause ground-loop hum. Of course, the first thing to check is the cables, as a bad cable can cause all sorts of noise. The pickup in most student models, and even some pro models, is a single-coil design, and they are prone to causing hum when they're in a locale that has a lot of AC electrical fields. The best way to test is just to move the guitar to another room and see if the hum is the same.

Hum in a certain locale can be caused by all sorts of things. But the biggest offenders are lamp dimmers, fluorescent lights, aquarium heaters, TV sets, and computers and monitors.

[Michael Brebes]

I had one pedal steel I was troubleshooting with ground hum. Found that the manufacturer took the pickup ground wire and attached it to the metal steel frame, then picked it up from another location and attached to the ground of the jack. Those connections can go bad over time. A clip lead from the pickup ground wire directly to the jack verified the problem.

[Dennis Detweiler]

He brought it to me. I checked it out, plugging it into my amp direct with different cables. It definitely had hum along with the sound of the guitar strings. I thought maybe a solder joint on the guitar input jack, but that didn't resolve the problem. I'm going to change the jack to eliminate that possibility. If it's not the jack, it has to be the pickup leads or the coil itself. This just started happening suddenly for him. The only experience I ever had with a bad pickup was on a MSA Super Sustain shortly after I bought the new guitar. However, it started producing feedback when certain notes were played. Maurice said, it sounded like a loose coil in the pickup. He sent me a new one free of charge and problem solved.

[Jim Kennedy]

A bad ground will definitely cause this. Jumper from the end plate the Jack is in to the changer. If that eliminates the hum, you have a bad ground. If your ground is screwed or bolted down at some point, clean it. Even a tiny amount of oxidation can foul the ground. I have greatly reduced or eliminated hum in several guitars by simply cleaning and tightening ground points that are screwed
or bolted in place.