470K resistor trick HSH Wiring

jaymenon

My guitar is HSH.
I need the middle single coil to see 250K only in position 3.

how do I do that please? And what am I doing wrong here?
https://i.imgur.com/GsMFsXD.jpg
https://i.imgur.com/5RT5qHP.jpg

That’s my resistor from position 3 to ground

but I get the feeling I need to make another connection to that pole of the switch - my electronics knowledge is crap - could somebody help please

jaymenon

Figured it out

Funkfingers

Looking at the photographs in the Sire S7 wiring Discussion, the middle pickup hot conductor goes to selector switch terminal 3 on the same pole as the resistor.  

In your circuit drawing, the problem is restricting the resistor to switch position 3 only. With positions 2, 3 and 4 physically linked to carry the signal from the middle pickup, the resistor will also be in circuit for those three pickup permutations.

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I suggest that you visit the DiMarzio website. Locate the product page for your middle pickup. Read the Tech Talk sub-page. It might be that DiMarzio recommends a 500k pot. This would negate all the faffing about with resistors an' t'ing.

Funkfingers

Also, in your circuit drawing, you have omitted a bridging connection to carry the pickup signals to the pole with the tone control sends.

jaymenon

Thanks Nigel, this is what I finally did. Diagram below, not showing the connections to the tone pots. The HBs are not coil-tapped in positions 2 & 4 so I wanted the full 500kΩ (except in position 3)

I connected the resistor from terminal 3 to the input of the volume control. The rotor of that same pole is connected to ground.
it sounds rather nice and seems to be working fine although I’m not entirely sure if I’m getting 250K in position 3

https://i.imgur.com/BL6WZ7G.jpg

jaymenon

That’s absolutely correct, and when my tone controls didn’t work I installed a bridging connection…!

ICBM

I think that’s right.

However, you probably *do* want the resistor in positions 2 and 4 as well, even if the humbuckers are not split - the combined impedance is still below that of the single coil alone. Your ears are the only real judge though...

jaymenon

ICBM said:

I think that’s right.

However, you probably *do* want the resistor in positions 2 and 4 as well, even if the humbuckers are not split - the combined impedance is still below that of the single coil alone. Your ears are the only real judge though...

Thanks both of you...

When I do @ICBM 'measuring potentiometer resistance in situ' trick, I'm still getting 500K on position 3 though - so I suspect my 510kΩ resistor isn't doing the job...

Re: the 510kΩ pole of the superswitch:
- should I connect the rotor to the other rotors
- then run a 510K resistor from terminal 3 to ground?

ICBM

jaymenon said:

When I do @ICBM 'measuring potentiometer resistance in situ' trick, I'm still getting 500K on position 3 though - so I suspect my 510kΩ resistor isn't doing the job...

That trick doesn’t work in this situation unfortunately. The meter can’t ‘see’ the resistor at all, because it’s on the other side of the pot and in parallel with the pickup.

The only way you could detect it would be the tiny change in total resistance at the peak, and that’s so small it would probably be within the meter error.

Funkfingers

This Discussion is descending into overthinking.

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This week, I had been mostly mulling over whether to use a 12-contact Oak Grigsby selector switch or a 24-contact four-pole switch, just in case I fancied modifying the circuit in future.

When I eventually bothered to inspect the rear access control cavity, the rout around the switch slot was too narrow to accommodate a double wafer switch without wood removal.

Decision made for me! 

FWIIW, my project guitar is routed HSS but I am installing DiMarzio HB/Track/Track pickups. No cissy coil splits!