Electric guitar pickups comprise a coil of wire that winds around six or more magnetic "poles." Pickup styles vary by manufacturer, but the two basic designs are single-coil and dual-coil. You can use a digital voltmeter, or multimeter, to test pickup coils for two common electrical faults: a short and an open. A shorted coil occurs when the coil connects within the windings, to ground, or to the poles. An open coil occurs when the wire is completely broken at some point within the windings. Both faults will affect the sound of the guitar.
- Skill level:
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Things you need
- Pickup manufacturer's specifications sheet (optional)
- Soldering iron
- Soldering flux
- Paper towel
- Wire cutters
- Needlenose pliers
- Wire strippers
- Digital multimeter
Use a screwdriver to remove the cover panel(s) for the guitar's electronics.
Disconnect the pickup leads from the volume potentiometer. Normally, you will have to desolder the leads with a soldering iron and flux. Use needlenose pliers to handle the leads. If the connections are old, or do not easily break free when heated gently with the soldering iron, you may have to clip the leads with wire cutters. Once you've disconnected the pickup, leave it installed in the guitar with the leads hanging free.
Prepare the pickup leads for testing by wiping away any flux with a paper towel. If the wire is long enough, you can also use wire strippers to expose ¼-inch of bare wire on each lead.
Set the digital multimeter to the "Ohms" or resistance setting. Place it on the "20K" or equivalent setting. Connect one probe to the "Ohms" jack, and the other to the "COM" or "Ground" jack (refer to the multimeter's manual, if necessary).
Turn on the multimeter. Touch one probe to the hot pickup lead, and the other to the ground lead. Observe the reading. For most pickups, a normal resistance reading will range from 4000 to 7000 ohms. Refer to the pickup specification sheet for the number listed as "DC resistance." If your resistance reading is out of the specified range, there is a problem with the coil(s).
Check the multimeter display for evidence of an open coil. If the resistance reading is far above the DC resistance range, or infinite (displayed as a "1" on the far left of the meter display), the coil is broken somewhere within the windings.
Check the meter display for evidence of a shorted coil. If the resistance is very low or close to "0," this indicates a short in the coil. Typically, a pickup with a shorted coil, an open coil or a "bad" DC resistance needs to be replaced.
Tips and warnings
- Before disconnecting the pickup, inspect the pickup leads and the spot where the leads join the body of the pickup. Sometimes, the leads or the pickup joint may be broken or loose. Also, check the volume potentiometer and pickup selector switch for loose connections. Any of these problems may produce changes in the guitar's sound.
- Disconnect the guitar from the amplifier before testing the pickups.
- When replacing or reinstalling a pickup, follow the manufacturer's wiring diagram.
- Take safety precautions when using a soldering iron. Wear ANSI-approved goggles and proper clothing. Ensure adequate ventilation, and never leave a hot iron unattended.
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