It’s a terrible feeling to discover that your guitar’s pickup isn’t working properly when you’ve got a gig coming up. Here are some general tips that will help you track down the culprit and get the electrons flowing again.
If your pickup is dead, first make sure your cable is good by trying it with something else you know is working, and then check the battery. While you’re doing that, also make sure that the battery terminal contacts aren’t corroded or bent out of shape, which can cause improper contact. Finally, check for loose or broken wires inside your guitar, especially at the output jack. Basic soldering skills are required to fix loose wires or replace the jack.
Maybe the problem is that your pickup sounds distorted or quiet. If you’ve checked everything on the above list and your guitar has an undersaddle (UST) pickup, check the saddle fit to make sure it’s sitting in the slot properly, making sure it isn’t leaning too far or hanging up on the edge of the slot. While we’re on the subject of USTs, here are a couple of tricks to fix uneven string balance: if a string has weak output compared to the others, make sure the string has a good angle over the saddle, because USTs rely on downward pressure from the strings. If everything checks out, a 1/4-inch long piece of foil tape stuck to the bottom of the saddle in the location of the quiet string may help bring it up to the right level. To tame a loud string, scrape away a 1/4-inch length of material from the bottom of the saddle with a razor blade or fill in the area of the loud string. If your UST has a low hum or one end is quieter than the other, check the fit of the saddle in the slot as well as how the UST sits in the slot (it should be centered and span the entire string area of the saddle).