Troubleshooting Guides

Be methodical!  The most important thing to remember when troubleshooting any problem is to be methodical.  A methodical technician straight out of school will often run rings around the most experienced guy in the shop if that experienced guy is working from rote memory of what he's seen before instead of using a methodical troubleshooting technique.

One of the "products" of the company I work for is a troubleshooting course that teaches just one thing, how to troubleshoot methodically.  Companies spend thousands of dollars to send a single employee to that course!

Here we present a set of methodical troubleshooting guides that cover a variety of situations from a general approach to identifying and eliminating noise to detailed, illustrated guides on how to troubleshoot a specific guitar.

Do I need a meter?  Some basic checks you can do with your ears, but for anything beyond the most basic troubleshooting you will need a multimeter similar to one of those pictured in the sidebar at the left of this page.  Such meters allow you to measure precise resistance between two points, battery voltages, and so on.  You needn't purchase an expensive meter unless you anticipate doing a lot of this type of work or anticipate one day working on high-voltage tube amplifiers and such. 

For troubleshooting guitars, an inexpensive analog (physical needle) meter is sometimes better than a more expensive digital meter.  This is because the analog meter makes it easier to "see" a capacitance in the circuit or a dirty pot.  On the other hand, a digital meter is more precise and usualy does not load the circuit as badly.  If you anticipate working on more than just guitars you may want to get a digital meter.  If you are doing this professionally you should have both an inexpensive analog meter and a good-quality digital meter.

Have an outlet tester handy.  You should also have an inexpensive outlet tester similar to the ones pictured below.  Not only can this inexpensive device save your life, it can help you track down noise problems as well!

 

Use a Ground Fault Circuit Interruptor  If you will be working on live line-powered equipment (i.e. equipment that plugs into a wall socket with an ordinary cord, not a "wall wart" transformer) you must use a GFCI similar to those pictured in the sidebar at left!  If you ignore this advice, don't come crying to me when you get killed or when you can't play anymore because the shock you got scrambled the nerves in your hand.  Also, please note that a GFCI is not a substitute for caution – even with a GFCI you can be killed or maimed when working on things like tube amps with high DC voltages and large filter capacitors.

Remove jewelry!  Working on a guitar, even plugged into an amp, is quite safe.  Likewise for working on stomp boxes and such powered by "wall warts" or small batteries.  But, working on any line-powered equipment is a whole 'nother story.  You can be shocked if a dangling chain gets into high voltage equipment and even low voltages can give you severe burns if a ring, watch, or chain on your body gets across a high-current source.  I've personally witnessed a heavy-duty socket extension be cut in half by a 28VDC power supply!  It's best to get in the habit of removing watches, rings, and neck chains every time you pick up your tools – even if you're working on a completely safe unpowered guitar this might save you a scratch in the finish.

Okay, now that you've read, reread, memorized and tested yourself on these basic safety rules let's get to the heart of the matter – troubleshooting that ornery gear!