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Jazz Std rewire - pot issue?

Discussion in 'Pickups & Electronics [BG]' started by greengoblin, May 6, 2010.


  1. Haha not the smoking kind!

    So I rewired my MIM Jazz last night with SD 1/4lb Basslines, CTS 250K pots and a switchcraft jack. Followed SD's diagram to a T:

    Seymour Duncan Diagram

    Pots: CTS Audio Taper pots EP885 from Guitar Parts Resource. Their site said they were for tone and volume control..

    Cap: Orange Drop .047uf 400v from Antique Electronics Supply...

    The problem I have is the volume pots only make a difference for about a 1/4 turn (at the right looking at the top). After that the pickup for that pot is silent (when turned farther to the left)...

    Any ideas on how I may have mis-wired? I know I compared the diagram many times before I bolted it up...

    :meh:
     
  2. Well, audio taper pots usually give you volume jumps around the last fifth of the rotation. You would have been better off with linear tapers for volume and audio for tone.

    That doesn't explain the muted output though.

    Have you checked the pots with an ohm meter to be sure they are functioning properly?
     
  3. Going to check the ohms tonight...

    One thing I wonder, did I get the wrong caps? (Not sure it would cause what I am experiencing.) But I got 716P Orange Drops .047uF 400v. They are huge though compared to the stock cap. About 3/4" log and about 1/4"+ wide.

    Markings on the cap: SBE 716P 400v 473J 0841
     
  4. Nope, the cap is fine.

    The physical size in this particular application means absolutely nothing. It all depends on the composition of the capacitor and it's voltage rating, which again, in this particular application mean absolutely nothing.

    Have you see any paper-in-oil capacitors btw?
    Absolutely huge...
     

  5. Yeah I opened up my V4 to inspect the caps. A cap job is on my things to do list. I pulled the death cap from it which happens to be .047 uf. hehe

    I test a Fender dual pot I had in the bad. It test fine with the upper being 500(test 443) and lower portion at 250 (285)..

    Going to have to un-do my work as I cant get an acturate reading when connected. Oh well, I have some nice tinned cloth cover wire I would've rather used anyhow. Perfect excuse. ;)
     
  6. Ok I am making some head room.. I started looking at Fender wiring diagrams and others and noticed some big differences between SD's and the others. I clipped all of the ground wires running down the right side and the finally wire to the jack.. This is giving me more volume overall, more volume in the lower range of the pots, but still a sharp spike at the end..

    Now the wiring looks more like the diagram below minus the ground going to #17:

    http://support.fender.com/diagrams/basses/0192400_02A/SD0192400_02APg2.pdf
     
  7. Point 17 is the ground for the shielding.
    That needs to be grounded!
     
  8. walterw

    walterw Supportive Fender Gold Supporting Member Commercial User

    Feb 20, 2009
    alpha-music.com
    and i don't see any way that clipping pot-to-pot ground wires would change anything since the pots are grounded anyway through the metal plate.

    i damn sure don't see how that could have increased volume. :confused:
     
  9. HUGE +1.

    I'm confused too.
     
  10. I dont understand it either. It could be just my ear/brain knowing I made a change and thinking it made a difference.

    Only other thing I can think that may have made a difference is that the control plate was unbolted from the body and loose, I put a piece of paper between the cap and cavity shielding(thinking maybe it was too close and grounding)..

    I may get some time tonight to do the rewire and will be doing it like the Fender diagram(which it pretty much is right now) and adding the #17 ground. Also I will test the ohm's on the pots while they are off.
     
  11. The control plate needs to be grounded to the shielding in one way or another.

    Remove the paper and make sure the plate touches the shielding.
     
  12. Ok I am back with testing news... I didnt get to test the pot values because I didn't take the entire control plate apart. but did find out some interesting info...

    -Added the ground at point 17 as Line6man suggested.

    This seemed to help and I get a volume change out of the entire sweep of the volume knobs. So I made headway and it seems to be working normal. Although I still have a slightly higher increase of volume out of that last 1/4" of knob sweep.

    -Added the ground wires along the right side as the SD diagram suggests

    With these grounds inplace in changed the whole ballgame.. The tone knob acted as a volume knob.
    So I removed the last leg of the right side ground from the tone pot to the jack. No difference.
    I then removed the portion from the bridge volume pot to the tone pot. No difference.
    Last I removed the last part of the right side ground (the jumper between the two volume pots) and the tone knob returned to normal status...

    so right now it is wired exactly as the American standard jazz wiring diagram...


    This all seems weird to me as this is a mexican Jazz that never had the point 17 ground from the beginning... The SD diagram should work normal since they promote it, but for me it did not.. Although I guess I am just an oddball. :p

    BTW, I love the tone of these SD Quarterpound Basslines. *drool*
     

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