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The third fluoro fails to light

Discussion in 'Electronics & Electrics' started by mhgarage, Sep 23, 2008.

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  1. mhgarage

    mhgarage Member

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    Three fluro circuits are connected to common AC 'boots' near the switch, but are electrically independent (own ballast, own starter, own tube)

    The third tube (furthest away from the electrics) often refuses to light when the switch is turned on. If I rotate the starter (i.e. breaking the contact) it will light. If I rotate the tube a few times (breaking the contact) it will light. If I 'smush' the switch, it will light.

    But yet it won't light when I turn the rest of them on.

    I suspect it is something to do with the sudden draw and the fact that the third fluro is the furthest away & hence highest resistance, but why does the starter not try again and again (i.e. flickering)?

    I have tried resetting all plugs and no go.

    Pic of installation is here:
    [​IMG]

    Any help greatly appreciated - it's a frustrating problem as no component seems to be the source of the problem.

    EDIT:
    Here's a circuit diagram.
    Problem tube is in orange (yes, I have tried swapping starters/tubes etc)
    [​IMG]
     
    Last edited: Sep 23, 2008
  2. Heatpipe

    Heatpipe Member

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    OK one suggestion is to reverse active & netural on the the third fluoro so it goes fluoro-->ballast.
     
  3. OP
    OP
    mhgarage

    mhgarage Member

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    Ok - how is this supposed to work? Just wondering before cutting up wire
     
  4. Heatpipe

    Heatpipe Member

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    Not sure just asked my dad to take a look, he said he's had the same problem before and thats the way he fixed it
     
  5. fabricator

    fabricator Member

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    I think it might be the cable length between the fluro and starter, its reducing the current flow through the end filaments. Often the starter sockets are next to one end of the tube.

    Just unscrew the starter and attach it temporarily with some shorter wires to see if that fixes it.

    I didn't have these problems when I made a lightbox, mind you I got a twin tube ballast and starters, plus only 2 tubes not three.
     
  6. sbadman

    sbadman Member

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    The key thing to remember is that the circuit is trying to strike an arc inside the flourescent tube (the job of a starter is to allow magnetic field to build up in the ballast and then collapse it to give a high voltage 'jolt' to the tube). If you're getting too much voltage drop the jolt won't be sufficient to strike the arc. If the starter can't function properly it won't be able to strike the arc on it's own. This can be tested by placing the tube and starter in the first fitting and testing operation, but given that it strikes when the starter is removed shows that to be the case.

    You may have to re-arrange the ligh box such that the started is located closer to the tube (physically & electrically), even replacing one tombstone to the type with an integrated starter socket as used in flourescent lit signs.
     
  7. P.YO

    P.YO Member

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    any reason why you can't put the circuitry above the tubes rather than to the right of the last tube? wiring should be shorter.
     
  8. OP
    OP
    mhgarage

    mhgarage Member

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    Solved the problem! Guess the resistance was too high
    Thanks for the help everyone
     
  9. sbadman

    sbadman Member

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    So what changes did you make? You can't leave us in the dark like this! (Pun intended :D)
     
  10. OP
    OP
    mhgarage

    mhgarage Member

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    Sorry! I made the lines to the starter much shorter, mounting it in the box on the base. IT now lights up properly - great success.
    Thanks for the help
     
  11. pipsqueak

    pipsqueak Member

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    does it matter if any wire is connected to any pin on the fluoro starer socket?
     
  12. Symon

    Symon Castigat ridendo mores

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    If you don't know that you shouldn't be playing with it.
     
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