How does exactly 250K/500K control work on American Pro Strat HSS and how to mod it?

Discussion in 'Stratocaster Discussion Forum' started by semka, Jul 1, 2018.

  1. semka

    semka Strat-Talk Member

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    I am new to HSS and just recently got American Pro Strat HSS 2018. I know it has a combo control 250K/500K, but how does it exactly work if in positions 1 and 2 both coils seem to be engaged or does it use 500K in position 1 only?

    From the official diagram, it seems that you can't split the coils on the humbucker. Is there a mod that would allow me to do it, e.g. by changing control to S1 switch like on Fender USA Pro HSS Guitar Center model from a couple of years back, so you can utilize 250K for SSS and 500K for when you need it for the humbucker?
     
    Last edited: Jul 2, 2018
  2. dirocyn

    dirocyn Most Honored Senior Member

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    The difference between 250k pots and 500k pots has to do with how much resistance there is between the signal and ground. You can get the electrical equivalent of 250k pots by adding an additional 250k resistor between signal and ground (parallel to the pots) to your existing 500k pot system. That parallel path through resistor to ground can be set up to work in specific switch positions, and it can probably be done using your existing switch.

    IDK whether your existing bridge pickup already splits the coils for position 2. If you already have 4 wires going from the humbucker to the switch, you're likely already set up that way.

    Humbuckers that are meant (by their manufacturer) to be split will have 3 or 4 wires. Soldering another wire where the two coils of a humbucker join (if there's not one there already) may involve soldering to a lug where hair-fine wire is soldered. Easy to screw up. Then the wire(s) that come from the middle between the HB coils need to ground (grounding out one coil, turning it off) and unground when you want the whole humbucker on. That can be accomplished either by using a push-pull switch on one of your pots, or by replacing your 5-way switch with a "super switch."
     
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  3. Guitaraxe

    Guitaraxe Strat-O-Master

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    Do you have a link to the official diagram?
     
  4. semka

    semka Strat-Talk Member

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    I asked Fender how to split coils and here's what they sent me and the official diagram.
     

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    Last edited: Jul 13, 2018
  5. Teleplayer

    Teleplayer Strat-O-Master

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    That's nice of Fender to supply the wiring advice for splitting in position 2. That wiring is sometimes called auto-split wiring.

    To make the change you need to add the red/green wires to the switch as shown, as well as the black ground wire to the adjacent lug. When in position 2, the switch contact closes so the red/green wires are shorted to ground. It means the bridge side coil of the humbucker is disabled in position 2 only.
     
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  6. semka

    semka Strat-Talk Member

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    Thank you for confirming - I was not sure if I fully understood how the mod was supposed to work. Ideally, though, I would also like to be able to split the coil in position 4 to have sort of SSS on demand.
     
  7. Teleplayer

    Teleplayer Strat-O-Master

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    Position 4 : Neck / Middle. In position 4 it wouldn't make a difference if bridge pickup gets split.
    Maybe you meant you like to split in Position 1? In that case you can replace one of the tone knobs with a push/pull. It could be used as a manual split switch so you have the choice to split the humbucker for Positions 1 and 2, or using the full humbucker as in the stock configuration.
    As a third option you could wire the two switches in parallel, so the push-pull tone knob will only be effective when the selector is in position 1.
     
  8. dirocyn

    dirocyn Most Honored Senior Member

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    Another option would be to set up the middle pickup on its own pot, but not through the switch. Then you set it up with master volume and master tone. That gives you 5 combinations choices with the switch, and can turn up any amount of middle with any/all of them. I'd probably set it like this: 1= both bridge coils in series, 2 = bridge single coil, 3=bridge sc + neck, 4 = open (you need an open switch position to be able to play middle pup alone) 5 neck pickup alone.

    For a live show it might be awkward though, some pickup changes would require both flipping a switch and adjusting the middle pup volume.
     
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  9. semka

    semka Strat-Talk Member

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    The volume knob already has dual 250K/500K pot, so wouldn't be more reasonable to put push/pull/S1 switch there? How should the wiring be done for that? Here is how Fender did it, except for single 250K pot with S1 switch (attached). They did it for position 4.
     

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  10. Teleplayer

    Teleplayer Strat-O-Master

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    IMO you are better off to keep the stock 500/250k volume control. The pickups have been designed to be work with the 250k/500k dual volume control and the associated treble bleed capacitors. Completely changing the wiring scheme to the one you posted would be a significant change to the overall character of the pickups. IOW you would be forced to choose to install either 250k or 500k which would be a compromise in some area, and it would be moving away from the original tone of the guitar.

    The mod suggested by Fender, or adding a push-pull tone knob are both relatively simple mods that will allow you to confirm if the split humbucker tones are useful or not.
     
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