P90 problem. What could be wrong?

Discussion in 'Luthier's Guitar & Bass Technical Discussion' started by kingsxman, Aug 14, 2006.

  1. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,551
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    I just picked up this early 70's Gibson SG pro the other day. I'm noticing a big difference in the output between the neck and bridge P90's. Neck is much hotter and bridge is very weak sounding. In the middle mode its almost a "quack" kind of sound..and even weaker than the bridge!

    I see that the bridge pickup is missing the cover on the p90. It also appears to be missing 2 screws that should be mixed in with the pole pieces in between the A and D and G and B strings. There are holes but no screws. Not sure if they're important or not. You can see from this link what I'm talking about.

    http://users.goldengate.net/~jgermann/SGbodycloseup1.JPG
    (click on pic for supersize!)

    This is my first P90's guitar so I'm unfamiliar with them.

    Thanks in advance.
     
  2. riffpowers

    riffpowers Member

    Messages:
    545
    Joined:
    Sep 15, 2005
    Looks like its probably a crappy P90,its certainly non original, just get a new gibbo one.
     
  3. John Phillips

    John Phillips Member

    Messages:
    13,080
    Joined:
    Mar 17, 2002
    Location:
    Scotland
    I'm not sure that pickup is non-original, it looks OK to me.

    On guitars where the pickups are mounted directly into the body (eg Les Paul Specials), the two screws that are missing are actually both the mounting and the height adjustment screws and are very long, thin woodscrews. On P90s which are fitted in rings and height-adjustable from the sides, these screws are replaced with bolts (with nuts on the underside of the pickup) which hold the cover on - so it's no surprise that they're missing since the cover is.

    One problem I've come across a couple of times with P90s is that if someone has taken the pickup apart for some reason, it's quite easy to get the magnets back the wrong way round - the natural way they 'want' to go (with opposite poles touching the center bar which the polepieces screw into) is wrong and produces a very weak, thin sound - almost no output at all. The correct way is with like poles facing, so the magnets will try to repel each other until the coil is screwed down onto them.

    If the coil meters OK (or if you get a strangled sound in the middle position too, which indicates the coil is not broken but is acting as a near-short on the other pickup), I'd make this my first guess. The correct polarity for the magnets is with the poles that repel from the top polepieces of the other pickup facing each other.
     
  4. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,551
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    Actually, I think they are original. That is my understanding anyway. Although I did see one pic of a SG Pro where its P90's said "Gibson" on the covers.
     
  5. kingsxman

    kingsxman Silver Supporting Member

    Messages:
    6,551
    Joined:
    Nov 8, 2004
    Location:
    Minnesota
    John, you sound like your onto something...

    What should the pickups measure for resistance? And is it obvious with the magnets how they come out and go in? I didnt take this pickup apart...previous owner did so I have no idea how this works....
     
  6. levelfrets

    levelfrets Member

    Messages:
    592
    Joined:
    Aug 11, 2006
    Location:
    Wilmington NC
    I would first check the resistance on the pup before you do any thing else. I think it should measure between 6K and 8K ohms. If it checks out then you might just have a bad switch. Hope this helps
     

Share This Page