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Thread: GFCI quiz

  1. #11
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    Quote Originally Posted by gar View Post
    181207-2111 EST



    A separate question is if a capacitor is connected between hot and neutral on the output side of a GFCI does the GFCI current transformer balance the two currents, in and out, to prevent tripping. I would hope so, haven't run the experiment.

    Some specific controlled experiments are needed.

    .
    It's supposed to be raining here tomorrow. Ill see if i can't run that "controlled experiment" in the afternoon

    Sent from my SM-G950U using Tapatalk

  2. #12
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    controlled experiment...

    When a 10 YO kid, knew if we tried to play the record player while sitting on the well grounded air duct to the gravity coal furnace, if we would get a good shock picking up the metal tone arm, we knew to reverse the plug.

    Years later, looked inside that cheap little tube (all American 5 set of tubes) radio/phonograph and there was a 0.1 uF cap to chassis from one side of the line cord, if no cap - LOTS of hum on the phonograph. Also 4+ mA 60 Hz leakage with the cap.

    The EMI filter on my 120 Vac input, 120Adc 14 Vdc output battery charger uses a SMPS to keep the weight down, the EMI filter has 0.2 uF caps to chassis and green wire. Cannot use on GFCI circuit.

  3. #13
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    Quote Originally Posted by GoldDigger View Post
    Many old phonographs and radios connected one side of the AC line to the metal chassis ...
    Quote Originally Posted by LarryFine View Post
    They were also among the first electrical devices to come with polarized plugs ...
    Installing a polarized plug will sometimes improve matters. If the device is old enough to contain vacuum tubes, it's probably time to replace the entire cord. Cleaning it and installing new non-conductive feet, and/or a non-conductive false bottom, might also help.

    I once had an old favorite 6-tube AM radio, probably built c.1960. Hot chassis, no power transformer, plastic case, chassis mounted to the case by sheet-metal screws through the bottom.
    It was on a freestanding steel shelf in an unfinished basement, and initially unknown to me, sitting on a small piece of metal junk. It made contact between the shelf and one of those sheet-metal screws, and energized the entire shelf. (no GFCIs at the time) Nobody got shocked because the basement walls leaked. It rained, there was water on the floor, and the points where the shelf legs contacted the wet concrete were steaming.

  4. #14
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    Older Phonograph shock experiment

    This thread takes me back to the 60's and a portable phonograph experience I have never forgot.
    As others have said the chassis could become hot if the plug was not polarized.

    I had bought my first electric guitar ( I was going to be a Beatle!) I could not afford the amplifier so I added a guitar jack to a portable phonograph to use its amp.
    I came home wet after a storm and started to play. Touching both the guitar strings and the chassis I got lit up.
    I was shocked to discover I did not have any talent as a musician

    I think that the leakage standards- to ground, have changed as the years progressed and thus older EMI filtering utilized larger caps than what would be allowed today.
    I recall experiencing several pieces of equipment that would trip GFIs when GFIs were still new.
    - Resistance is Futile ..... (if less than < 1 ohm) -

  5. #15
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    Quote Originally Posted by ELA View Post
    I was shocked to discover I did not have any talent as a musician
    Nice pun!

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