Two F4T5/CW bulbs failed

Discussion in 'Electrical Forum discussion & Blog' started by Bill Arden, Jan 19, 2008.

  1. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    I bought three of these small 4W "under cabinet lights" (W-mart, Lights Of Am...) Model 7104

    I am annoyed to say that one bulb failed after a month and another after two months.

    The filament is open on one side with a dark color on the bulb.

    Replacing the bulb fixed the light.

    I am trying to figure out why the filament would fail as I had these lights are on all the time (24/7 path lights to let me leave off the main shop lights)

    I am tempted to take one of the lights apart to see if they used a "continuous run" capacitor type circuit to heat the filament using the main Square wave output.

    Edit: Yes it does use a "continuous run" filament circuit just like the cheep CF bulbs.
    I'll hook it up to the scope to see if I can add a Neon bulb starter to it.

    Edit again: Nope. The light needs the filament to be hot in order to keep it light.
    Last edited: Jan 19, 2008
  2. alternety

    alternety Like an engineer

    Messages:
    650
    Location:
    Washington
    Think LED.

    I am not fond of LOA either.
    Last edited: Jan 20, 2008
  3. jimbo

    jimbo Plumber

    Messages:
    8,997
    Location:
    San Diego
    Philips rates an F4T5 at 6000 hours life, about 6 to 8 months@ 24/7. Rated life is the hours that ONE HALF of the population of bubs is expected to achieve. Half will be less, half more.

    LOA makes crap, so I would not expect any of their bulbs to last all that long. They do also warrant their bulbs and fixtures, so you might give them a call.
  4. Bill Arden

    Bill Arden Computer Programmer

    Messages:
    584
    Location:
    MN, USA
    The start cap in the unit was 3.3nF.

    This seems high since the start cap for a 13W CF is around 2.2nF

    Testing shows that 1nF is enough to start even the older (darkened) bulb.

    I wonder if they used the wrong capacitor ?
  5. lampman42

    lampman42 New Member

    Messages:
    7
    Buy a new fixture

    Lights of America are crap fixtures, yes they are cheap but you get what you pay for. I would buy a new fixture.
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