Series wiring has low volume/grounding hum

Discussion in 'DIY Strat Forum' started by Trousers, Oct 12, 2021.

  1. Trousers

    Trousers New Member!

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    A09E8CB1-D328-40BC-AE44-41C5F9B71B48.jpeg DB821EFD-3A7B-4B30-8DE2-2763703ECFEE.jpeg Hey guys, I’ve been trying to give my strat the ability to put the pickups in series via a 4pdt putting the guitar into series mode and an SPDT being the selector between neck+mid and bridge+mid.
    For some reason, the guitar has extremely low volume and is very buzzy. I can’t understand why and I have triple checked my solder joints, checked that the volume pot still works, changed out the output jack, etc. I’m thinking maybe there’s some form of excess resistance present in this circuit that I don’t understand. The switching system works exactly as intended, but the volume is far too low to be useable in any instance. Here’s some pics of the wiring and the diagram, let me know if you need better pics or anything.
     
  2. ThreeChordWonder

    ThreeChordWonder Senior Stratmaster

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    If it were me I would start by UN-coiling those ground wires from around the hots.

    Nice little transformers you've built there.

    Next write down a table of what switch positions and what combinations you want and post it up here for us to have a look at.
     
  3. Trousers

    Trousers New Member!

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    oh shoot, that’s how the prewired came. I didn’t even realize that would be occurring.
    As for switch positions right now, all I’m trying to make function is 4pdt ‘up’, parallel where the normal strat pickup selector does its thing.
    4pdt ‘down’ is series where the SPDT selects my pickup combinations (bridge+Middle or neck+middle) and the selector switch is inactive, save for going into the common output on the switch to feed to the volume pot.
     
  4. TheWorldsAStage

    TheWorldsAStage Strat-Talker

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    Buzzing could be an indication that something that should be connected to ground is connected to hot instead. String/bridge ground, pot casings, etc.

    Focusing just on the "normal part" of the wiring diagram, with parallel pickup combinations, it looks right to me and should work.

    I'd bust out the multimeter and start checking the switches and wiring to make sure things are making good connections and connected to only what they should be. Those mini toggles can't take a whole lot of heat before the red plastic starts melting. Things that are directly connected or switch contacts that are connected should be 0 to very low ohms.
     
  5. Trousers

    Trousers New Member!

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    Since the 4pdt was the new addition before it started behaving this way, I assumed it might have melted inside. I put a new one in, making sure to solder quickly and then wait for it to cool, then solder another point. So I think the integrity of the switch is alright. Continuity and resistance look alright. I was starting to think the way the middle+ to output might not have been correct, but parallel mode should function as normal and it doesn’t