Guitar Electronics Troubleshooting

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by Obiwannabe, Feb 29, 2012.

  1. Obiwannabe

    Obiwannabe Member

    Mar 16, 2009
    I did a quick search and looked through some threads, but found nothing to general.

    So my Epiphone SG is having problems. It does not want to produce sound. I plug my jack in, but no sound.

    My question is this:

    I want to know how to troubleshoot the problem. Testing pots and what not. I have a voltmeter but don't know where to begin. Can someone help me out? I know this is a Über-noob question, but i would really like to be able to do this on my own.

    I have soldering experience so i should be ready to handle that no problem.

    Any advice would be great thanks!
  2. scotchtape800

    scotchtape800 Member

    Mar 9, 2011
    If you have can take the jack out, you can try running a continuity test between two points in the circuit to see if there's a break somewhere...

    Like putting one end on the hot lead of a pickup and testing the hot lead at the output.
    Also on the ground side too.

    I'm a noob at this too but that would ID if there's a break somewhere, then you could keep testing points along the way to determine where the bad solder joint was, or if something came loose.
  3. OlAndrew

    OlAndrew Member

    Nov 6, 2007
    Sedona, Arizona
    Set your meter to ohms, a low range. If you can work on the guitar through an access port or something like that , it's easier. Plug in your cable. One meter probe on the center pole of the cable plug, one on the side, just like the jack would contact. You should see a low ohms reading. 0 = dead short somewhere, infinite or really high means open circuit.

    You have tried a different cable, I hope? OK, we see open. The most likely places for failure are the switch, a known weak point on Epis, or a bad solder joint or broken wire. Wires frequently break at the jack, it'll work a bit loose, you try to tighten it, and the jack turns and breaks the wire.

    Work in steps, following the wiring, until you hit a good connection, the last thing before that will be your fail point.
  4. Rockledge

    Rockledge Member

    Jun 15, 2011
    An easy way to isolate problems is to use wires with a gator clip on one end and a 1/4" plug on the other. Start at the point where the pickups connect to a pot of switch (whichever comes first) and work backward following the signal path.
    You will get a lot of hum while doing this, but it is normally the quickest way to run down a problem you cannot see.
    One clip on the first place the wires go from each pickup, then between the ground and switch output hot, ground and volume pot hot IN, then the volume hot out with the pot turned up.
    This way you will find out up front if you have a pickup with a bad coil, a bad switch, or a bad pot.

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