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What voltage should I measure??

Discussion in 'General Electronics Discussion' started by chatenever, Aug 10, 2014.

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  1. chatenever

    chatenever

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    Aug 10, 2014
    Hello all. This is my first post on this forum. My kitchen has recessed lighting fixtures with four-pin fluorescent bulbs. One is not working. Swapped bulbs with one of the working fixtures to eliminate the bulb as the problem. I then measured voltage between each pair of pins in the receptacle (six measurements in all) and got zero voltage on each. I didn't know what voltage I should be reading, so I checked the receptacle on one of the working fixtures. I got the same zero volts!! How can these bulbs work if I'm reading zero volts at the receptacle??? I tried various voltage ranges on my VOM, including AC and DC.

    There is no separate ballast on these fixtures. The ballast is built into the light bulb. Any ideas how I should proceed?
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    1) Put your multimeter away
    2) Call an electrician.

    Yes, there will be a voltage across the pins in some way if a lamp works. I never recommend placing the probes of some unknown meter into mains power outlets.
     
  3. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Steve is right.You are messing with high voltages that your meter cant handle. Some light fixture have igniters that can fry your standard meter in an instant. If your up to the task, turn off the breaker to the lights and replace the ballast inside the can. Most of these types of ballasts will release the wires by pushing a tiny screwdriver into the hole next to the terminal strip.
     
  4. chatenever

    chatenever

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    Aug 10, 2014
    Ok, I've got it. Thanks. The wires that supply the receptacle are of a voltage and/or frequency that I cannot measure with my VOM. That means that there must be a ballast output at the other end of those wires. I removed the recessed fixture above the ceiling and the wires that supply the receptacle emerge from a junction box above the ceiling that does not appear to have a removable cover plate like a standard J-box. I suppose its possible that the ballast is located inside that box? Are you familiar with that physical arrangement? How can I gain access to the J-box so I can access the ballast?
     
  5. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    And I would advise getting a voltage detector so you can verify that the breaker you switched off was the right one.
     
  6. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    You may have to replace the entire unit.

    Be *very* careful because the mains can kill you. A perfect way to have that happen is to be holding something in one hand, and using a screwdriver in the other.
     
  7. Tha fios agaibh

    Tha fios agaibh

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    Aug 11, 2014
    Yes, put your meter away. Its a bad Ballast
    Remove the can from the ground (there should be enough slack in the wiring) The ballast will be in the jbox above the can. Replace it being sure to observe wire colors.
     
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