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I recently got myself a Nordstrand MM4.2 to pair with an active Mojotone 2-Band Music Man Clone. This is my very first attempt to mod an electrical instrument, and I thought it would be so much easier than what it looks like. I followed the wiring diagram that came with but I'm not really sure where or what I messed up, so I thought I might ask for help here before I take any further action.

Here's what it looks like:

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Click for full size

Since I want it wired in parallel, I connected the red & black wires from the Nordstrand PU with the hot, and white/green/bare wires are soldered together to the ground. At first I tried to solder the ground on the backside of the volume pot but I horribly failed (hence the aftermath), so I took a washer to ground all the wires somewhere else since I thought it's a brilliant idea. The single green wire soldered to the washer (ground) is connected with the bridge, and the battery is connected once on the preamp (red) and once with the jack (black) as usual.

When I plug my bass in without a battery, I can somehow hear it making sound (I have to turn my volume knob all the way up and the amp about the halfway for it), but only when I'm touching the control plate with my hand. I guess this means my pickup is working fine, but why does it make sound only when my hand's put on the control plate?

When it's plugged in with a battery it's dead silent, except it does make some minimal static noise when I mess around with the volume and EQ. I can also hear the sound coming out of my amp when I tap the control plate or the bridge, but nothing on the pickup.

Now here's the thing. I don't own a multimeter so I can't troubleshoot anything on my circuit. I suspect it's either my volume pot I cooked while I desperately tried to ground everything on it, or maybe I forgot to ground somewhere. Grounding parts is also the thing I can't seem to understand at all, even after watching a handful of youtube tutorials.

So if you could tell what the problem might be, I would really appreciate your help. Thanks in advance!

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    Is the bridge connected to the ground, and is the preamp grounded through some other wire? To me it sounds like it's floating and touching it adds just enough capacitance that the preamp gets some signal.
    – ojs
    Feb 26, 2022 at 11:21
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    Multimeters aren't expensive, and if you are going to make forays into any re-wiring, forget it without one!
    – Tim
    Feb 26, 2022 at 11:26
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    A picture of the wiring diagram might help. The bunch of different colours all strapped to a floating ground looks highly dodgy.
    – Tetsujin
    Feb 26, 2022 at 11:28
  • here's the picture of the wiring diagram: imgur.com/a/UDEMzKr Feb 28, 2022 at 18:15
  • I think both the bridge and the preamp are connected to the ground by the washer, but I'm not 100% sure about it. The green wire with the white tip coming from the left side of the washer is the one from the bridge, while the red wire on the right side of the washer is connected to the volume pot. Feb 28, 2022 at 18:30

1 Answer 1

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A multimeter is not a bad investment if you are trying to do such things.

It hard to make a diagnose from just this one picture. You should provide at least the wiring diagram (else we cannot say a lot about the wiring). As long as you do want to wire the pickup in parallel the wiring of the pickup looks fine to me.

Grounding pot casing is generally a good idea, but mostly to get rid of a potential source of noise. Doing this requires a capable soldering iron and a bit of time, as the large size of the pot casing spreads the head very quickly.

Do you have this washer connected to the jack? If not you won’t close your circuit.

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  • Do I have to connect the washer to the jack? If so, to which part of the jack should I connect it? Anyways, I appreciate your help. Here's the picture of the wiring diagram: imgur.com/a/UDEMzKr Feb 28, 2022 at 18:21
  • @pairoscales In the diagram you see three wires on the jack. The middle one leads to a a kind of triangle, which is the ground sign. Everything that is grounded should be connected to this part. The diagram would be something like this (starting at the jack): (JACK) mass→ground, ring→battery, tip→volume pot. (VOLUME POT) one connector to ground, one connector to output of preamp, (PREAMP) also connected to battery, EQ pots, to ground and to pickup, (PICKUP) also connected to ground. Every thing that is ground should be connected to the ground part of the jack.
    – Lazy
    Feb 28, 2022 at 18:50
  • @pairoscales So the black wire going from preamp to the casing and the right contact of the volume pot is the wire that grounds the preamp. The other wires of the pickup (which is white, green and the shielding) go to ground too, as well as the grounding wire to the bridge. All of these should be connected to the middle connecton of the jack. I see them all connected to the washer, but I do not see where the black cable coming from the middle connection of the jack goes to. This one should as well be connected to the rest.
    – Lazy
    Feb 28, 2022 at 18:56
  • I've bounded the wires from the pickup that goes to ground (white, green, shield) and the grounding wire to the bridge with a new wire, and then connected this wire to the right contact of the volume pot. I've also connected this right contact of the volume pot to the middle contact of the jack so I'll have to guess the circuit is now closed. Still not working. Could it be that I've really cooked the volume pot while trying to ground everything on the casing? Mar 21, 2022 at 9:48

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