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Really strange pickup problem !!

Discussion in 'Pickups & Electronics [BG]' started by Bassamatic, May 17, 2012.


  1. Bassamatic

    Bassamatic keepin' the beat since the 60's

    I bought a DiMarzio P/J set from a fellow TB-er, and installed them today, and the sound was very strange.

    On both pickups, there is a HUGE difference in level and tone between the top 2 and bottom 2 strings.

    On the P pickup, the E is normal, the A is funny and out of phase sounding and the D and G are about 1/4 the level.

    On the J pickup, the E and A are very low, and the D and G are loud and normal.

    To be sure it was not my wiring, I connected the wires from each pickup directly to an input cord and tested them - the result was the same.

    When I received the pickups, one of the 4 magnets on the J pup were loose, I wonder if the magnets have been monkeyed with? Are they supposed to be hot glued in? How to test the polarity?

    I'd like to make them work, so your comments will be appreciated.
     
  2. I'd double check the colors you hooked up. IIRC all dimarzios can be series or parallel connected. Lotsa info on their web site.
     
  3. Bassamatic

    Bassamatic keepin' the beat since the 60's

    That is a good thought, however when I received them, the Black and White wires are already connected to each other and nicely shrink wrapped. I use the Green for ground and the Red for hot. This also would not cause a difference between the top and bottom 2 strings.

    I checked the series resistance of the pickups and they are close to spec. The phase seems to also be the same for all poles of both pickups, but when testing this, the voltage output of the D and G section of the J pickup is much smaller than for the E and A. Makes no sense to me.
     
  4. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    That's the problem right there. The two magnets should face the poles with the same polarity, so they will want to push each other away. Right now they are probably attracting, so that kills the magnetic field over the pickup.

    Each half of the pickup should have the magnets opposite. So if the E-A is North in, the D-G should be South in. In this photo the small black dots are designating North.



    DP123_Model_J_1.jpg
     
  5. Bassamatic

    Bassamatic keepin' the beat since the 60's

    What great information! Now I know what the dots mean. On one of the P halves - one of the magnets seems to be reversed. Testing it with one magnet of the other pickup - one side repels and the other side attracts - it seems that it should be the same for each side to a common magnet, yes? OK - one was loose and upside down That takes care of the P (I hope).

    For the J pickup all are installed correctly - so what is it's problem?

    Thank you.
     
  6. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    Are you getting a thin sound when both pickups are on, or when each is soloed? Do you have the P wired up the right way? It sounds like one half of the P is out of phase with the J.
     
  7. Bassamatic

    Bassamatic keepin' the beat since the 60's

    The P is working and sound great. It is quite revealing when the pickup is wired directly to an amp!

    For the J - One half od the J pickup is really weak - when measured on the bench, and when wired directly to a cable to the amp. Since the halves are wired in series, I don't understand how 1/2 could be bad without affecting the series resistance or the sound of the other half.

    I sent an email to DiMNarzio - we'll see what they have to say. I wonder if they would warranty the J?
     
  8. SGD Lutherie

    SGD Lutherie Inactive Commercial User

    Aug 21, 2008
    Bloomfield, NJ
    Owner, SGD Music Products
    When you say "measured on the bench" what are you referring to? Measuring the resistance?

    Are you sure the magnets are correct on that half?

    Also, you say the P is fine, but earlier you said; "On the P pickup, the E is normal, the A is funny and out of phase sounding and the D and G are about 1/4 the level. "

    Is that with both pickups on? If the D and G sound thin with both pickups on at the same time, then one of the two coils is out of phase with the other pickup. Don't forget they are both split coils.
     
  9. Bassamatic

    Bassamatic keepin' the beat since the 60's

    Thank you for your continued patience with this.

    When I reversed the magnet on the P Pickup, it now sounds fine. Somehow it must have come off in the past and been replaced improperly. I re-glued it.

    For the J - I measured the voltage on my bench by connecting the pickup to my analog voltmeter, placing a screwdriver between the poles and taking it away quickly. I usually do this to check phase. The good side generates about 1/10 volt, and the weak side barely moves the needle.

    I am testing them by themselves to eliminate all the variables, using clip leads direct to the leads on the pickups. The J pickup is out of the bass at the moment so I can inspect it for any other physical issues.
     
  10. Bassamatic

    Bassamatic keepin' the beat since the 60's

    I have checked everything on the J pickup, physically. One side is just really weak for some reason. My friend suggests bad magnets. I guess I'll have to return them.

    Thanks for the input.
     

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