Electronics Overhaul on MIJ J-Bass

Discussion in 'Pickups & Electronics [BG]' started by IanTrout, Dec 23, 2017.

  1. IanTrout


    Dec 23, 2017
    Hi Everybody, it's my first post here :)

    I have a 90's MIJ j-bass, and it's really great, but I feel that I need to upgrade it to get that extra mile out of it.
    I was thinking of a complete overhaul - pup's and the pots/cap.
    I would really appreciate some help with two questions:

    1. What diameter pots do I need to get the MIJ bass? I measured them and it looks like 0.25", but I wanted to make sure. Any good places to get the right size CTS pot's?

    2. My bass is a bit too bright for me (it's brighter then the average j-bass), so I was thinking of getting new pup's that will give a deeper sound. Any suggestions?

    Regarding the pup's, I know I could probably make do without replacing them, by adjusting the height and volumes, but I just want to get a new sound out of it :)

    Thank you in advance!
  2. rojo412

    rojo412 Sit down, Danny...

    Feb 26, 2000
    Cleveland, OH.
    Welcome to TB!

    1) Typically, I think a 3/8" threaded shaft is what was used for most pots on Fender stuff. Though it's MIJ, so they may have used something slightly smaller, but you'd find that out pretty quickly if you bought a 3/8" pot and it didn't fit into the plate.
    If you take the pots out of the plate, measure the threaded shaft area and that should be the answer.
    If they are smaller, but you want to use something like CTS pots, you can just ream or drill out the plate until they fit.
    CTS pots are all over the place. Best Bass Gear, Allparts, Stewmac, you basically can't swing a dead cat in a guitar/bass parts site without hitting CTS pots.

    2) There's certainly no shortage of pickups to choose from and equally as many opinions on the topic as well (if not many more).
    My personal recommendation would be for the Dimarzio Area J pickups. They are humbuckers, which gets rid of the 60 cycle hum found in single coil pickups, but they have a very traditional, smooth sound to them. I've put them into a few basses and always dug the results. Lots of output, well balanced tonality, great for a mellower J sound.
    Fender also makes the SCN pickups, which I liked for a very similar reason. But given the choice, I'd go with the Dimarzios.

    Hope that helps. TB is full of a lot of great info.
  3. IanTrout


    Dec 23, 2017
    Thanks for the info, it was really helpful!
    For some unknown reason I didn't think about drilling the plate, that would probably solve the size issue and I can get the CST's I want :)
    And I think i'm going to take your advice on the pickups!

  4. somebrains


    Feb 7, 2017
    I have a harness somewhere from a GZR PJ set.
    250k pots, and whatever the cap value they use is a good start.

    A lot of guys I know don't think the MIJ electronics were bad, they think the soldering isn't the greatest.

    Unless the pot is dead/dying, my reason to swap is if it's a 500k.
    I would reflow whatever components I was keeping.
    Do a proper copper tape job with 3m tape, make sure the adhesive is electrically conductive.
    Rewire your existing pickups in series.
    This is the cheapest bang for buck path.

    If you just want to buy a simple solution, there are several set of EMGs in the FS section.
    Add an Aguilar preamp, that tends to breathe some depth into active J's.
    This will be a little more expensive, but a used J set and preamp aren't that $$$.
  5. IanTrout


    Dec 23, 2017
    Thanks for the reply!
    It's not that the electronics isn't good, and from the looks of it, the soldering looks decent enough.
    I just wanted to upgrade it, and I wanted to find a useful project as well, so the bass was chosen :)

  6. somebrains


    Feb 7, 2017
  7. flatwound62p


    Apr 24, 2017
    I've got a MIJ Fender P that I replaced the wiring and pots in. Definitely worth doing it IMO. Had to drill to make CTS fit.

    If TB member HEADbass is still doing harnesses I can totally recommend his top quality work, that's what I used in my P bass. Here's an example for a JB SOLD - Jazz Bass loaded control plate
  8. bigtone23


    Dec 10, 2014
    Denver, CO
    Save the pickup swap until very last. Adjusting them can make a big difference. It's not always necessary to go changing electronics, but I always change the jack to a Switchcraft if the current jack is not at least of that quality.
    Things to maybe try first:
    -String choice also can help get you your darker tone, and it's cheaper than pickup swaps. Nickel wounds, pressure or ground wounds or cobalt flats have a darker tone.
    -Check and see if your pots are 500K. If so, switch to 250K and it will tame the brightness a bit.
    -Also check your tone cap. If it's a .022uF, replace with a .047 (which is a great place to start), .068 or even .1uF. This will darken it more when rolled off. I keep a half dozen or so .015uF 50 volt caps around, just keep stacking them in parallel until you find the tone you like. Add up the values and either install that value cap or just keep those in place. Being 50V, they are quite small and a stack of 4 is not very space consuming.
    -Since this is a J bass, if you decide to change the pots, you may want to consider linear taper volume pots. I do this with my VVT basses and it really makes blending have a much wider range/finer adjustment. There are many threads that discuss this.
  9. Unless there is a problem with the existing pots, or you wanted different values or tapers, you won't gain anything from changing them. Don't waste your time and money on that.
    Pilgrim likes this.
  10. Pilgrim

    Pilgrim Supporting Member

    The MIJ Fenders are very well thought of. If you change anything, save the original parts and don't lose track of them.

    And I fully agree about the pots. Unless they have problems, there's no need to change them.
  11. IanTrout


    Dec 23, 2017
    Thanks for the advice!
    The whole overhaul thing was a 'spur of the moment' kind of deal, but after I finally got my guitar open, the pots are actually 500k and not 250k, and the cap is a really cheap type that didn't even have any markings on it, so I'm not sure what is its value (my cheap fluke at home doesn't measure capacitance).
    So I guess the new pot's will make difference.

    I also want to replace the output jack to a Switchcraft to avoid any noises I've been getting recently.
    Also, I have no idea who did the soldering on the electronics but it's not the best quality job I've ever seen (to put it mildly).

    I have my project after all :)

  12. I also currently play a (MIJ) Fender Jazz Bass 1990's and the Pots are Alpha's 250K. The capacitor is your standard Orange drop that you'll find in all Fenders. If you want CTS, then you will definitely be doing some drilling. Which I hope you are good at? Good luck!
  13. NKBassman

    NKBassman Lvl 10 Nerd Supporting Member

    Jun 16, 2009
    Winnipeg, MB, Canada
    I think you'll definitely want to put a series/parallel switch in. I did that in 2017 and immediately wondered why I'd waited so long.

    Currently using Nordstrand Jazz Blades and like them. I wouldn't describe their overall tone as particularly deep or bassy, but they sound great. A nice, balanced, vintagey vibe.

    Also recently put the new-ish GHS Balanced Nickel strings on my jazz and like them quite a bit. Very thick sound without getting muddy or overly dark.
  14. fermata

    fermata Guest

    Nov 10, 2015
    The cap construction, materials, size, markings, etc. etc. are irrelevant in a passive tone circuit. Do you like how the tone control sounds when it's turned down? Then it's the right cap value. If it's too bassy, try a smaller value; if it's too bright, try a larger value. (What's in there now is probably .047 uF.)

    500K Ohm pots are appropriate for this application; if you want to lose a little bit of treble, go to 250K. Are the volume pots linear (B) or audio (A or log) taper? I think linear taper volume pots are the way to go on a two pickup bass: turn one back to 75% or so and then blend in the other pickup to taste (I like 500K pots for this, as you lose less volume turning them down; at 50% of the rotation, they're equivalent to 250K pots). However, the tone control needs to be audio taper, or it won't work right.
  15. somebrains


    Feb 7, 2017
    Someone put one of these in the Jazz I just picked up.
    After a year playing Warwick $$'s I needed a change, but I now appreciate the ability to switch from parallel and series on the fly.
    I rewired my $$5 so I can get series and parallel out of the singles rather than full MM humbucker.

    When I was younger I was about the hottest I could get.
    I would have been one of those dudes driving a big block Chevy just barely held at a stoplight, but my little brother worked at Sears Point raceway.
    I had a steady supply of 108 octane gas for a 13:1 compression small block.

    It's all about the experience, build out everyone's ideas bc Jazz parts are plentiful and inexpensive.
    Try a bunch of passive builds, try passive pickup active preamp, try active active.

    If you see an old set of Bart 94's for $100 buy them and keep them for later.

    Really understand what the instrument does to an amp and cab, but those interactions will spawn your favorite setup of X bass with Y amp and Z cab to produce that perfect sound for that moment.

    Then you go build out S bass for T amp and U cab for another setup.

    Then another, and another, and another, then you'll get why some of us run pedals and preamps thru discreet tube/Class AB/Class D power amp bc you're running out of floor space.
  16. somebrains


    Feb 7, 2017
  17. bigtone23


    Dec 10, 2014
    Denver, CO
    The series/parallel switching is pretty killer on a J. I did it on my Peavey Foundation and even though I don't use series much, it is a great option to have.
  18. somebrains


    Feb 7, 2017
    Parallel is really good with humbuckers, you catch a lot of nuance and depth.
    Series butches up your singlecoils without the inevitable loss of harmonics when you start trying out hot wound J's.

    There is also something to be gained by changing pot and cap values.

    You can further refine your tone by trying out different control layouts that would affect load on pickups.

    Bad soldering will negatively affect top shelf electronics.

    These are all relatively inexpensive things a person can try at home with a quality solder station, multimeter, and a little bit of time.