Waz's MMB-4

[wazkelly]

Agree with trying blend pot options first as not much room left in control cavity.

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[RalphH]

Here's another wiring option to consider that was employed on the G&L L1000 series basses of the late 1990's. This setup allows two humbucking modes plus a single coil option.

The pickup on the L1000 appears to be wired the same as the GFS, (3 conductor series wired humbucker with centre tap + case braid) so theoretically this should work for you too.

The G&L had a 3 position, 2 pole toggle switch which are quite expensive (and hard to find) so during my experiments I configured a 2 pole, 3 position rotary switch to do the same job. Looks good too.
The rotary switches I've used are only 5 bucks from Jaycar, and the only customising is the reworking of the shaft to accept a fluted knob. And yes- they fit (at least in my case) in the cavity of the MMB bass with a bit of minor sanding.

[Simon Barden]

Surely Position 3 will be out of phase with itself, so give a very thin sound that's probably not bothering with? And as the current flows the wrong way round just one of the coils, then it won't be humbucking (I think).

[wazkelly]

Ok, bear with me. It's a bit difficult to tell from your photos etc., but the original configuration of the Belcat blend/balance pot should have been something like this:
Attachment 27614
The black ground would be connected to either the top left lug or bottom right (with respect the the above orientation), and each of those lugs has a link to the pot case. The red hot from the volume would either be the bottom left lug or top right and have a coated wire linking between those two lugs. Normally, your parallel pickups/coils would then connect to the middle lugs.

However, because your pickup coils are in series rather than parallel we need to connect each coil across the resistance side of each half of the pot, which requires some re-wiring. Essentially, when at the centre detent the signal will then go through each coil in turn rather than through the resistance (mostly) and turning the knob away from the centre will bypass one coil or the other.

First step is to disconnect the pot case link from the lower right lug, otherwise it will short your signal to ground. Next, disconnect the wire link from between the bottom left lug and top right lug.

Then, connect the pickup and volume wires like this:
Attachment 27615
That *should* get you what you want. The sound of the pickup may be slightly different in the centre position compared to what you're currently hearing, due to the change to the way the coils are loaded. And, you'll probably find the balance works a bit more... switchy. That is, you may not hear much change until it's almost fully turned one way or the other and then you'll hear the coil drop out quite quickly. Hopefully

Another option would be to just remove the blend/balance pot entirely and replace it with an On/Off/On mini-switch to select the coils as one/series/other.

OK, so I have wired it up this way and as predicted not much difference in sounds and if anything just a tad thinner at centre position which should be in series.

Reverted back to original blend pot setup and played around with various combinations and best sound was just hard wired in series with blend pot effectively doing nothing.

Now starting to consider either mini DPDT on-off-on switch or a rotary one as suggested by Ralph however not sure on how to wire up either switch type. Thankfully Jaycar Electronics are less then 1km from where I live and stock both parts but the rotary switch has a long shaft that would need to be cut down. This is the mini DPDT they have and wondering which wires go to which lugs?



Thanks, Waz

[WeirdBits]

This should do it for an On-Off-On, series in the middle position and shorts the respective coils when up and down:

[wazkelly]

Thanks Scott, i will give that a go.
Cheers, Waz

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[geddyfan]

This should do it for an On-Off-On, series in the middle position and shorts the respective coils when up and down:

Hi Waz...this is what I did on my RC-4 build as well. The result was less than impressive from my POV, but it seems to work. I need to make some adjustments, tho (pickup height)...maybe they'll improve the result when I'm done? We'll see...

[wazkelly]

Thanks mate

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[wazkelly]

Wired up the DPDT mini switch earlier tonight and that works & sounds best out of all the combinations tried so far.

Thanks guys for all your ideas, guidance & assistance.

Next job is to dig a bit more timber out in the control plate cavity as there is a square plastic terminal block for belcat pre-amp with lots of wires coming and going that is preventing everything fitting in an already cramped space. Don't own a dremel and not keen spending the coin for just this one job. Might have to use a chisel instead unless someone has a bright idea for cutting/recessing at 90 degrees inside a 30mm wide trench which is just on 38mm deep?

For it it sit vertical, thickness is about 6 or 7mm thick whilst horizontally I would need to go about 18 to 20mm deep and drilling in via jack socket hole seems most logical way to go? Will ponder this for a few days before attacking it.

[DarkMark]

I’m not usually one for product endorsement but I brought a Dremel and it’s my favourite toy at the moment. As an engraving tool it is 100% better than the engraving pen I was previously using.