Mmb-4 control problems

[Graham]

Hello, I have just wired up my mmb-4 kit as per the wiring guide on the pitbull guitars website. This is my first build and the bass works (yay!) but the controls are odd. The first knob (furthest from the lead socket) does nothing when turned except cut all sound out when it's turned all the way down. The second has a different tone at the mid point, and then the same tone turned all the way up or down. The third knob does nothing. My wires coming from the pickup all looked exactly the same as the wiring diagram except in the 'bare wire and two wires twisted together' one, I have just 2 wires twisted together, and the red one from the diagram is a bare and a red twisted together. Any ideas? Thanks for your help.

[WeirdBits]

Can you post some photos of your wiring, it’ll make it easier to diagnose and resolve. Different kit batches can have different wire colours so it helps if we can see what’s what.

[wazkelly]

Hi Graham, PBG store states:

Pit Bull Guitars MMB-4 Electric Bass Guitar Kit Includes:

Basswood body
Maple Neck (bolt-on) and Blackwood (engineered rosewood) Fretboard
34″ Scale with 24 frets
Chrome plated hardware
Humbucker pick up
2 volume and 1 tone knobs
Chrome machine heads
Lead
Strap buttons
All electronics (pots, caps, wires, etc)
Set of Bass Strings
FREE Shipping – Anywhere in Australia
Level of Soldering Difficulty: Novice
This kit contains everything you need to build a complete, playable guitar, except your choice of finish.

Wiring diagram found here.... https://www.pitbullguitars.com/wp-co...MMB-4_2014.pdf


The control plate comes pre wired and if connected like above it should work? I butchered mine and added a pre amp so not much help in that regard. The diagram is suggesting that volume controls are working independently off each of the humbucker coils and also has a master tone. Therefore, when all on '10' it should sound quite full and meaty but as you back off one volume the level would drop as well as the depth of tone, then switching the other way does the same on the other coil. The difference in sounds is very subtle between front & rear coil and when combined with drop in output level you may end up just leaving both volumes wound flat out.

Cheers, Waz

[Graham]

Thanks for your quick replies, really appreciate it. My problem is that in the middle control, the loudest point is the mid way point, whereas I'm guessing it should be when turned up full. When I am home from work later I will post some pics of the wiring. Quick question in the meantime, is it possible I have heat damaged them with my soldering iron? I'm not great at soldering, and particularly for the first pot, I took a while getting some solder on the surface. Temp set at 250 degrees.

[wazkelly]

Weirdbits aka Scott is the best person to answer most of your questions.

Just wondering if the 1st or 2nd volume controls seem to have a center detent position, meaning that when you get to the midpoint you feel a slight click as you move past it? This may explain what is going on with the middle control.

If possible can you take and post photos of the underside of the control plate to help us see what has been pre-wired?

[WeirdBits]

It’s possible to damage the pots with heat, but it sounds more like the issue is the pickup wires are mis-connected which is why I was waiting on photos. The wrong wires connected to the second pot could potentially result in the ‘mid way point’ issue etc, so it’s best to see what’s connected where before assuming it’s a cooked pot.

[Graham]

Hi, please find attached pictures. I hope its clear for your to see. I followed the wiring diagram as closely as possible. The differences in my wires are my green twisted wire was made of 2 wires not three like the diagram, and the red wire which is one wire on the diagram is twisted consisting of two wires on my pickup.

[Graham]

The green and bare twisted wire Ive soldered to the top of the pot, I butchered the soldering a bit but its attached. I did a cleaner job of the black wire to the hoop on the same pot, and the red and bare wire was reasonably cleanly attached to the hoop on the second pot.

[WeirdBits]

Ok, it's as I suspected. The factory typically ships humbucking pickups like yours with their coils linked in series, whereas the wiring diagram is designed to link them in parallel (as is traditional for a MM pickup).

So your pickup currently has its coils linked like this:
Bare & Green - 'Coil 1' - Red - join - White - 'Coil 2' - Black

First, as a common point of reference, the pot with the green capacitor nearest the jack is the Tone pot, the middle pot is Volume 1 and the other pot is Volume 2.

You currently have the pickup's Black (hot) wire connected to Volume 2, which is correct. But, you have the joined Red-White pair connected to the Volume 1 pot, which is what is causing the problem (or maybe one of the problems). With that wire pair connected to the Volume 1 pot it's working as sort of a balance/fade across the two coils, which is why it's loudest at the middle point... it starts cutting out one coil or the other as you turn it to either side.

If you want to test what the pickup sounds like with the coils in series all you need to do is disconnect that Red-White pair from volume 1, cover the bare tips with some tape and give it a try. The pickup will be at its loudest and Volume 2 will control the volume.

To wire it traditionally, as intended on the diagram, all you need to do is disconnect the Red-White pair from Volume 1. Unsolder the tips to separate the Red and White wires, then connect the White to the back of Volume 2 (with the Green and Bare pair), and connect the Red by itself to the middle lug on Volume 1. That should allow Volume 1 and Volume 2 to control Coil 1 and Coil 2 respectively, and all should be well in the world.

Now, it's possible there could be some other issues. The 'all or nothing' effect you've been getting with Volume 2 could be a result of the Red-White mis-wiring, or it could be a bad/cooked pot. You'll need to correct the wiring and then see.

The Tone pot not changing the sound could also be tied up with the mis-wiring, but it could be something else. See what it sounds like once the re-wiring is done. If it is still not changing the tone then we'll need to investigate further. In that case, check that the bare legs of the Green cap haven't been squashed onto the pot or its lugs (which could short it out), and if so, try to post some close-up pics of it before trying to 'un-squash' it as the legs are easy to break.

Good luck.

[Graham]

Thanks so much for your help.

I'll give the wiring you've advised a go tonight. If I separate the red and white wires, do I connect the white to the top of the pot as I have done with the green and bare, and connect the red to where it is now in the side hoop?

It is volume 2 that is loudest in the middle. Volume one will cut all of the sound out of the bass as it is turned down. I have had another go trying out the controls last night. The tone knob does work, it just makes very subtle changes-perhaps this is correct?