How to Stop a Grounding Noise in an Electric Guitar
- 1). Connect your guitar directly to your amplifier. If the hum is present, rotate the guitar in relation to the amp. If the hum level changes dramatically from almost none to heavy, it is likely you are using a single coil pickup and a transformer in the amp is inducing a hum. This is normal. Change your playing position relative to the amp to reduce the noise.
- 2). Replace the guitar cord if the hum remains steady regardless of amp position. If this cures the problem, the original cord is the likely culprit. Check the solder joints on the cord for damage. Try the amplifier plugged into another circuit, perhaps in another room or location to rule out problems with the wall outlet.
- 3). Toggle the "Ground" switch if your amp is older and so equipped, if the hum persists. Removing your hands from all metal parts on the guitar may cause a hum to get worse. If this is the case, or if all other tests fail to affect the hum, it is possible the ground wire inside your guitar is compromised.
- 4). Open the electronics cavity on your guitar. A wire connected between pickup electronics and the bridge will be evident. This wire grounds the bridge, strings and tuners to a common point with the electronics. If a multimeter is available, test continuity between the bridge and the other connection point of this grounding wire. Any reading other than zero indicates a problem.
- 5). Replace a questionable grounding wire by using a soldering iron to disconnect soldered joints. Often the bridge connection is made with a wire wrapped around a mounting screw, so you may need to remove the strings and the bridge to access the bridge connection. Replace the grounding wire with a similar or heavier gauge insulated copper wire.
Source...