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Thread: Xenarc CCFL brightness reduced after modification - please help me debug

  1. #11
    Newbie
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    Jul 2004
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    Right I've just found out why my high voltage wire extension is causing the CCFL brightness to be reduced. Here's what I did...

    • Rip the screen apart and remove the extended segment of the high voltage cable.
    • Switch on and observe that brightness is back to normal (good, I suppose).
    • Reintroduce an equivalent length of extended high voltage wire on the bench
    • Switch on and observe a slight decrease in brightness but nowhere near as bad as when the wire was routed through the in-dash enclosure
    • While switched on, prod the extended cable around with a plastic pen and observe that the brightness is reduced when the cable comes close to the grounded chassis. ('aha' says Scouse)
    • Observe a marked decrease in brightness when ~4cm of the extended cable is taped parallel to the grounded chassis
    • Then I get really creative and take a 2cm x 1cm piece of of aluminium foil and wrap it round a part of the extended cable and then offer a ground lead up to the foil...
      I didn't even get to touch it the spark jumped about 1mm and rebooted the Xenarc.
    • added one wrap of insulation tape around the wires and repeated the foil test.
      no spark this time but CCFL still momentarily went off when I touched the foil

    So my conclusion from all this is that it's a capacitive effects that are causing my brightness problems. I'm not too hot with capacitor theory, going to have to dig out my course notes , but I know they pass AC pretty well which would explain this completely.

    I'm now thinking my cable is sh1t!

    So I started looking at the PC case modding community as they use CCFLs to pimp their rigs. Saw this and wondered if the cable and sleeving they've used in this product will be any better than my test lead wire. Too late, just ordered it. I'll be calling Visualux too tomorrow. Words of encouragement please.

    James

  2. #12
    Fusion Brain Creator
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    Mar 2005
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    it's nto that it's capacitative, it's that the cable's insulation is breaking down. you need better cabling. Perhaps cabling from a cheap computer case CCFL?

  3. #13
    Fusion Brain Creator
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    and the problem with your extension is that it has the wrong ends

  4. #14
    MySQL Error Scouse Monkey's Avatar
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    Dude. As I said before - visualux if you are in the UK (mouser or digikey if you are not).

    they will have the proper wire and proper connectors for you to make an extension with.

    We got this very same problem with the backlight upgrades from the metal chassis. SO much so it actually ended up blowing an LCD (and Jerry) up (sorry jerry, had to laugh)

  5. #15
    FLAC coucouillu's Avatar
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    Quote Originally Posted by Scouse Monkey
    Dude. As I said before - visualux if you are in the UK (mouser or digikey if you are not).

    they will have the proper wire and proper connectors for you to make an extension with.

    We got this very same problem with the backlight upgrades from the metal chassis. SO much so it actually ended up blowing an LCD (and Jerry) up (sorry jerry, had to laugh)
    Scouse,

    I've seen the "backlight upgrade" thread is closed...Have you open an other thread?

  6. #16
    MySQL Error Scouse Monkey's Avatar
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    Quote Originally Posted by coucouillu
    Scouse,

    I've seen the "backlight upgrade" thread is closed...Have you open an other thread?
    not yet. We are planning stuff to put in it.

    We will post when we get the new tubes.

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