I got a little Les Paul Jr and I'm replacing the bridge pick up with a Seymour Duncan JB. I've got it mounted and the other pick up removed. Stock pickup was just two wires soldered. The JB has 4. No clue where to begin.
This is my first time ever. Everything is connected. I wouldn't say I'm skilled at all, I've just seen it done a few times. When I plug it up there's the usual hum of the amp but when I hit a string I hear it dimly fade in and out.
1) Desolder everything.
2a) Take the pickup leads (leave pickup installed) - hold the hot lead against the tip of a cord plugged into an amp and the ground lead against root - strum the strings. If you get sound great, if not, you probably have a pickup issues.
2b) Take a multimeter and check the pots - make sure that you have a resistance change as you turn the pot - if you don't, you need a new pot(s).
3) Solder the leads back to the volume pot - apply heat to the pot/wire and touch with solder. Look for a nice shiny finish. If it doesn't look shiny, try again.
4) Wire cap and jack wire to the middle lug of the volume pot (assuming 50's wiring) and the cap to the tone pot. Again, check for shiny connections.
5) Check all ground connections (shiny)
6) Check the jack wiring (redo soldering - shiny) and make sure that when everything is in place, the cord won't short out touching a ground wire.
7) Plug it in and hopefully you have sound!
This is a strange coincidence of a thread, i did the exact thing to the exact guitar with the exact results a while back. Well my pickup was a 57' but i ended up using a JB. My problem was a cold soldered ground to the pickup base.