Video of pickup capacitance as it's wax potted

Discussion in 'Pickup Forum' started by Antigua, Jul 12, 2020.

  1. Antigua

    Antigua Senior Stratmaster

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    I made a video of a Strat pickup being wax potted in order to show the relationship between time, wax uptake and capacitance. This is a continuation of an experiment started here https://guitarnuts2.proboards.com/thread/8959/potting-rate-uptake-change-capacitance






    The drop is right about 10 seconds in, so all the times can be correlated to the video time stamp -10 seconds. I set the camera up so that you can see bubbles emerge from the pickup's coil.



    0:00 127.62pF +0.00 .
    0:10 126.11pF -1.51
    0:20 131.09pF +4.98 .***
    0:30 144.24pF +13.2 .***********
    0:40 152.38pF +8.14 .*****************
    0:50 157.30pF +4.92 .********************
    1:00 163.73pF +6.43 .************************
    1:10 170.81pF +7.08 .*****************************
    1:20 172.81pF +2.00 .******************************
    1:30 174.57pF +1.76 .********************************
    1:40 176.74pF +2.17 .*********************************
    1:50 176.87pF +0.13 .*********************************
    2:00 177.76pF +0.89 .**********************************
    2:10 177.84pF +0.08 .**********************************
    2:20 178.11pF +0.27 .**********************************
    2:30 178.78pF +0.67 .**********************************
    2:40 178.87pF +0.09 .**********************************
    2:50 179.14pF +0.27 .***********************************
    3:00 179.21pF +0.07 .***********************************
    3:10 179.89pF +0.68 .***********************************
    3:20 179.90pF +0.01 .***********************************
    3:30 179.91pF +0.01 .***********************************
    3:40 179.92pF +0.01 .***********************************
    3:50 179.94pF +0.02 .***********************************
    4:00 179.96pF +0.02 .***********************************
    4:10 179.97pF +0.01 .***********************************
    4:20 179.98pF +0.01 .***********************************
    4:30 179.99pF +0.01 .***********************************
    4:40 180.01pF +0.02 .***********************************
    4:50 180.01pF +0.00 .***********************************
    5:00 180.02pF +0.01 .***********************************
    6:00 180.03pF +0.01 .***********************************
    7:00 180.02pF -0.01 .***********************************
    8:00 180.00pF -0.02 .***********************************
    9:00 179.97pF -0.03 .***********************************
    10:0 179.95pF -0.02 .***********************************



    After the pickup cools, the final capacitance is 185pF, as the wax cools and contracts the coil.

    As it can be seen, the wax potting increases the overall capacitance from 127pF to 180pF, and then after cooling, 185pF, for a total increase of 58pF. Also, most of the absorption happens between submersion and two minutes, and then it's essentially flat until the pickup is allowed to cool, but nevertheless there is a steady positive uptick, so it slowly takes on slightly more wax as time passes until it peaks at six minutes.

    One take away is that, it seems to me, that the coil is fully penetrated by was without the need for vacuum potting, at least with this Strat style pickup. It might be a different story with a plastic bobbin, but I doubt it.

    Another is that the capacitance increases with wax potting, 58pF is similar to an added 18 to 24 inches of guitar cable length. This can drop the resonant peak by 100Hz, give or take, depending on the inductance and the overall capacitance. Not easy to hear, but not impossible, if the resonant peak is somewhat low to begin with.

    Lastly, if a person were to "lightly wax pot" a pickup, they would need to pull it at about 45 seconds, if they were to do nothing else. The earlier experiment showed that if the pickup is pulled at 30 seconds, the wax will just be clumped up on the outside of the pickup, because the pickup's surface temp is still below the melting point of the wax. But there's another technique that could be used; dip the wax in the vat really quickly, and then stick the pickup in the over at 150 degree F, or maybe leave it in direct sunlight, and allow the wax and the pickup to heat up with only the volume of wax that's coated around the pickup, and the final result should be waxed coil containing less overall wax than had the pickup been submerged for two minutes or longer.