Buzz help. Model J Fender

jobo4 · #1 01-04-2013, 05:52 AM

Hello tech gurus,

I'm a little out of my depth on a project to wire my Model J pups into a V push/pull (series/parallel), V push/pull (series/parallel), Master Tone configuration. this is the first time I have tried to use push/pull pots. After my innitial effort I have buzz. I used the Dimarzio wiring diagram (attached) and then connected the three ground wires (neck pup, bridge pup, bridge plate) to the back of the tone pot. When I touch the strings the buzz does not go away or even get quieter.

What should I be looking for as a likely mistake? I'm on the verge of just chucking the push/pulls and wiring them in to standard volume pots which I have done successfully many times in the past.

I should add that I had Ultra Jazz pups in it before and they were wired VVT (no push/pull) and were dead quiet. Also, I've been using the search function a lot and gather that the issue is electrical field noise rather than 60 cycle. Just looking for any insight. I assume that the fact that my cavity is not shielded is probably not the issue, due to the fact that the Ultra Jazz pups made no noise in the same unshielded cavity.

jobo4 · #2 01-05-2013, 09:12 AM

Bump. Any ideas?

joelb79 · #3 01-05-2013, 10:07 AM

Sounds like your grounds might need touching up. Also, you can ground the poles on the DP123's and that will help as well. Make sure that everything is soldered correctly, any cold solder joint can cause some noise injection. I'd double check the grounds to the back of the pots/ground/shield as well. Alternately, move the grounds to a star and make sure the star is touching all the shielding. Also make sure you measure 0 ohms from all shielding points. If not, they could inject noise rather than shield it.

jobo4 · #4 01-05-2013, 10:31 AM

Thanks Joelb

DiabolusInMusic · #5 01-05-2013, 10:47 AM

If you touch the strings/bridge/metal and the noise goes away you have a shielding issue. If you touch the strings/metal/bridge and the noise gets louder you have a grounding issue.

Since it seems like a shielding issue here is what you do, there are more guides here with pics if you need them

-Line the pickup and control cavities with copper foil tape, tape up over the cavity edge over any screw holes so when you screw the guard down the screw pierces both pieces of copper tape.

-Line the pickguard (if needed) and the pickup surrounds, wrap the pickups with electrical tape so they don't touch the copper. Also ensure you wrap a little extra copper over the edge of the pickup cover.

-If your pickups are routed in their own cavity you will need to solder a wire from the pickup cavity shielding to the control cavity. If they all share one large cavity just line the whole thing.

-Solder a wire from the pickup covers (that is why you add the extra over the edge) into the control cavity.

-Solder your ground wire to the shielding in the cavity so it all gets connected.

That should be everything, aluminum tape will work but it is MUCH easier to work with copper, it tends to give more consistent results. Copper foil tape can be sourced locally from stained glass supply shops, I did far to many basses with aluminum before I found out you can get copper tape locally.

I hope that helps, I hate hum so I like to see people get the most out of their basses. As far as I am concerned a humming bass is not a stage ready instrument.

SGD Lutherie · #6 01-05-2013, 11:03 AM

Check the output jack. Make sure you don't have the hot and ground mixed up.

jobo4 · #7 01-05-2013, 06:37 PM

Thanks to Diabo and SGD. Pickups are also microphonic. Giving up.

SGD Lutherie · #8 01-05-2013, 07:24 PM

Quote:

Originally Posted by jobo4

Thanks to Diabo and SGD. Pickups are also microphonic. Giving up.

Did the magnets become unglued from the bottom of the pickups?

They shouldn't be microphonic.

jobo4 · #9 01-05-2013, 07:46 PM

They are still encased in wax. Hard to tell.

jobo4 · #10 01-05-2013, 07:50 PM

And by microphonic I mean that when I slide my fingers across the pole pieces it makes a noise like you are scratching a microphone screen.

joelb79 · #11 01-06-2013, 03:03 PM

Model J's can come apart easily. They are glued into the covers, and also the magnets and spacers for the poles are glued on the bottom. This makes the pickup deeper than a typical J pickup. The extra depth of the pickup means you cannot use the foam that came with the bass (like Fender's notorious Jazz bass pickup foam), you usually need to find a custom solution or cut the foam that dimarzio gave you in the packaging. If you screw the pickup in with a lot of pressure on the bottom, the magnets and pickup bobbins tend to un-glue from the bottom and pickup cover, leaving the metal spacer that holds the poles to move around freely. this means the poles are loose then and create a microphonic condition. witnessed this first hand with my own mistake.

I'd take the pickups out and see if that happened. If that happened, either have dimarzio repair them (BEST AND RECOMMENDED OPTION) or glue them together yourself. However, be warned; it's not simple and knowing something about magnets and pickups will seriously help you if you are attempting this yourself. We can help, but if you loose the orientation of the magnets its not going to be easy and could alter the sound of the pickup dramatically.

SGD Lutherie · #12 01-06-2013, 03:10 PM

Quote:

Originally Posted by jobo4

They are still encased in wax. Hard to tell.

They aren't. They have hot melt glue on the bottom to hold the magnets on. The magnets often come loose.

Like Joel said, they can be taken apart fairly easily. I've done it many times. All you have to do it pry the cover off.

Quote:

Originally Posted by jobo4

And by microphonic I mean that when I slide my fingers across the pole pieces it makes a noise like you are scratching a microphone screen.

That's because the poles are not grounded. You are likely not hearing microphonic noise. If they are squealing when you stand in front of the amp, then they are microphonic.

jobo4 · #13 01-06-2013, 08:08 PM

Joel and SGD... Thanks again for the technical advice. I pulled the pups out today and there is no visible evidence that anything came unglued. They look exactly like they did when I pulled them out of the box. Hopefully that means they are still glued properly.

As for grounding, I think what I must have done is instead of soldering the green wire to the back of the pot, I inserted my cranium into my rectum. :-\

Seriously, one good thing has come of this experience... I figured out that Vol Vol +PP tone series/parallel is better for me than PPV, PPV,Master tone.

My last effort still came up short, so I'm heading to a tech on Tuesday to correct the errors.

Many thanks again.