Measuring pickup resistance at the output jack?

Discussion in 'Pickups & Electronics [BG]' started by ThingsAbove, Apr 27, 2019.

  1. I measured the DC resistance across the output jack terminals of my new MIM passive P-bass with both pots wide open at 4.99kOhm

    That seems kinda low to me. If anything I would have thought that measuring it in-circuit would show slightly higher resistance than measuring the pup on it's own. I haven't measured it out of circuit yet.

    Can someone take me to school on this?
     
  2. megafiddle

    megafiddle

    May 25, 2011
    The tone pot is isolated from the measurement by the tone cap. There is no DC path through that part of the circuit.

    With just the pickup resistance and 250K volume pot in parallel, and the total resistance known, the pickup resistance can be found by product over difference:

    (250,000 x 4990) / (250,000 - 4990) = 5092

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  3. Doesn't that seem like a low DC resistance for a passive P pickup?
     
    Last edited: Apr 27, 2019
  4. megafiddle

    megafiddle

    May 25, 2011
    That would be low for a typical alnico magnet pickup. Those normally range around 10.5K.

    If the output level seems normal, could just be a ceramic pickup wound with less turns of heavier wire.

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  5. okabass

    okabass

    Mar 19, 2005
    Finland,Lahti
    Normal P Bass pickup DCR is around 11 kΩ. Measured like you did, it should show some 5 % lower value. So I think there could be 1) non correct measuring (check the meters battery) 2) non-standard PU, 3) PU malfunction (like wiring, damaged coil)
     
    Last edited: Apr 28, 2019
  6. Output is slightly hotter than my other passive basses (measured on my oscilloscope). But the tone is very bright.

    My digital multi-meter correctly measures known values of resistors.

    In Fender's advertising for the Players P-Bass Special Edition it says they've used a newly designed Alnico 5 pickup:
    "Respecting heritage while maintaining innovative spirit, the fat, punchy Player Series split-coil Precision Bass middle pickup is packed with legendary Fender bass tone, turned up to 11 for modern ears."
    So, could part of the "turned up to 11" be due to using larger magnet wire with fewer turns? I can't find any specification on the web for the new Players series pickups.
     
  7. okabass

    okabass

    Mar 19, 2005
    Finland,Lahti
    One possibility is, that the both coils or PU halfs are around 10 k, and then connected In parallel. But just guessin. You should check the PU, how it is made, measure only the PU etc.
     
    Last edited: Apr 30, 2019
  8. I have some new pots and a pickguard on order. When I swap out the pots and shield the cavity I'll measure the pups on their own.
     
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