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Todays Puzzler.The mystery of electricity

Discussion in 'Home Power and Microgeneration' started by j, May 31, 2012.

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  1. j

    j Guest

    The spare bath in my house was added in the '60s. There is a fixture
    over the sink with a double light socket, one faces left and one faces
    right,it's one piece. Common at one time.

    So today I wanted to put a fan in this otherwise unused bathroom. I got
    an edison base adapter and screwed it in one of the sockets. Plugged in
    the fan and nothing. Didn't matter how it was switched. So I went off to
    get a bulb to test the other socket. When I screw in the bulb, it does
    not light but the fan goes on. The fan seems to be fine and the bulb is
    completely dark. Unscrew the bulb and the fan turns off.

    WTF!

    Who cares to gamble a wild ass guess?

    Obviously the fixture has to go! But very strange.

    Jeff
     
  2. Bob F

    Bob F Guest

    Maybe you have a 220V circuit with 2 110V bulbs wired in series.
     
  3. Jim Wilkins

    Jim Wilkins Guest

    Maybe the torque on the bulb wiggles a poor connection.

    jsw
     
  4. Winston

    Winston Guest

    I concur with your diagnosis, Dr.

    Except that the 'cold' resistance of an incandescent
    bulb would pass plenty of current to power a series-
    connected fan in a ~120 V circuit.

    --Winston
     
  5. Bob F

    Bob F Guest

    Which is what he said it does.
     
  6. amdx

    amdx Guest

    That's also my guess, when the bulb is screwed in it compresses
    a connection in the socket.
    Mikek
     
  7. Vaughn

    Vaughn Guest

    The above explanation sounds more likely than the 240-volt guess.

    I also like soft light in a bathroom. I choose slow-starting CFLs these
    days. Guys shouldn't try to pee in the dark, but full-bright light is
    piercing when you get up in the middle of the night.

    Vaughn
     
  8. Winston

    Winston Guest

    Yup. As Gary Heston points out, the series connection
    might have been on purpose.

    --Winston
     
  9. Jim Wilkins

    Jim Wilkins Guest

    Easily checked with two bulbs of different wattage.

    jsw
     
  10. Winston

    Winston Guest

    Yup.

    Though, personally I'd want to shut off the supply and
    open the fixture box to determine what other surprises
    lay in wait. :)

    --Winston
     
  11. j

    j Guest

    On 5/31/2012 4:06 PM, j wrote:

    I took apart the fixture today and found out why. Let's review the
    evidence:
    Note the "one piece".
    Note that the fan worked fine, it's not that it struggled on partial
    voltage, and if it was wired in series, the bulb (an incandescent) was
    completely dark.

    This removes the series connection theories. And certainly the 220v
    theory that depended on it.

    So, what we have in the socket in the dead middle is a U shaped flat
    copper strip. The hot wire is soldered to this and each end of the U
    contacts a bulb center contact. For the ground threaded part: there are
    two of these with a solder tab. They are facing outward, of course, but
    the tabs are together and the ground wire is soldered to the left socket
    that had the bulb screwed in. The tabs are in turn soldered to each other.

    So, what happened?

    The connection between the two tabs broke apart. When the bulb was
    screwed in it pushed it's ground tab out enough to contact the other tab
    and send power through it's "ground" connection.

    The winner is: Jim Wilkins

    Why didn't the bulb light? The "hot" contact was oxidized enough to be
    an insulator.


    I have pics and video...

    Jeff

    Unscrew the bulb and the fan turns off.
     
  12. Winston

    Winston Guest

    Thanks for closing the loop, j.
    Well done, Jim.

    --Winston
     
  13. Brian Gaff

    Brian Gaff Guest

    Sounds like someone has done my favourite trick to make bulbs last
    indefinitely and put them in series.
    Brian
     
  14. Jim Wilkins

    Jim Wilkins Guest

    Bad grounds and intermittent connections cause the oddest symptoms.

    In Army Signal Corps electronic school the instructors doctored AGC
    glass fuses to remind us to check them with a meter, not just by
    sight. They heated one end cap to melt the glue and pop off the cap,
    then inserted too-short heavy bus wire and even blue ("the fuse blew")
    paper to make it look good again. I caught the 1 Amp fuse with 12 AWG
    wire inside it visually and went up to joke with the instructor about
    it, then we watched most of the class pull out the phony fuses, give
    them a puzzled look, put them back and continue troubleshooting.

    jsw
     
  15. m II

    m II Guest

    -----BEGIN PGP SIGNED MESSAGE-----
    Hash: SHA1


    Fuses on electric stoves/ranges are bad for that. They commonly break
    the link where it bends, just outside of sight. The fuse looks good
    through the glass, but there's no continuity.

    The repeated cycling off/on and the resultant thermally caused
    expansion/contraction probably work hardens the metal where it's
    already been stressed by the bend, causing the fractures.

    So, yes...using a meter is a very good idea.


    mike






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  16. Vaughn

    Vaughn Guest

    Yes, I learned the hard way. Early in my career, I spent two days
    trying to troubleshoot a simple problem with the tail lights on a pickup
    truck. They had the oddest symptoms! My meter seemed to be of no help,
    giving all kinds of strange readings. In the end, it totally defeated me!

    In desperation I took the truck to a dealer. They said "No problem!"
    When I got it back, I discovered that they had installed a ground wire
    between two certain frame members under the truck, which totally cleared
    up the problem. They had probably seen dozens with the exact same issue.

    Vaughn
     
  17. j

    j Guest


    It is now. It's an unused bathroom with the water off. I wanted a fan in
    the window and there are no outlets. I ran an extension over to a
    kitchen outlet.
    I was in the audio biz at one time and grounds are all important.

    As far as vehicles, grounds are always suspect.

    If you clip your volt meter on to a known good ground, and have
    everything "on", then you should have near zero volts at other grounds
    you test.

    It's easier/faster to test volts than resistance. Testing resistance
    when you have clear suspects.

    Of course, common problems become known after a while. But, I'm at
    the stage in my life that I never want to have the same problem more
    than once.

    Jeff
     
  18. Vaughn

    Vaughn Guest

    Yep! That's exactly what I do. I've found zillions of bad connections
    with a voltmeter. It's just a simple application of Ohm's law.

    Vaughn
     
  19. Mho

    Mho Guest

    Stick with your failed Internet business.

    ------------
    "m II" wrote in message Fuses on electric stoves/ranges are bad for that. They commonly break
    the link where it bends, just outside of sight. The fuse looks good
    through the glass, but there's no continuity.

    The repeated cycling off/on and the resultant thermally caused
    expansion/contraction probably work hardens the metal where it's
    already been stressed by the bend, causing the fractures.

    So, yes...using a meter is a very good idea.


    mike
     
  20. The Real Bev

    The Real Bev Guest

    When did 3AG fuses become AGC? Serious question...
     
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