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Thread: LCD Backlight Upgrade

  1. #571
    Variable Bitrate numbers's Avatar
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    My initial thoughts were to use 150mm straight 3mm od ccfl tubes arranged horizontally. I don't really know how many because I haven't tested with any yet. The stock lilliput uses about 412mm of what appears to be 2 or 2.6mm ccfl. That would equal just under three 150mm tubes. I guess maybe six or eight?? I figured I'd order ten and go from there. The 150mm tubes will probably wind up taking about 2 watts each. This design is less efficient than two W tubes, but should be cheaper. I estimate that each W would be about 600mm, which should draw about 4.5 watts. This makes about 9 watts total for the twin W's, while eight 150mm tubes totaling the same 1200mm would draw closer to 16 watts. That's almost twice as much for the same total length of ccfl. Now I'm not sure how much the custom W design would wind up costing, but the 150mm straight tubes shouldn't be much more than $5 a pop.

    Anyway, the 150mm tubes would be connected in parallel with a twist. Rather than run a wire from each output on the inverter to each tube, you would have one wire coming from the inverter and connecting to the same side on all tubes, and another wire coming from the inverter connecting to a capacitor soldered to the other side of each tube. I don't know for sure how well this would work. I need the tubes to test it on. It should work in the mind of someone used to working with low voltage dc and whatnot. Few people fully understand the workings of high voltage ac and I only wish I could say I was one of them. It is possible that wiring it like that could cause enough stray capacitance to goof with the tubes. At any rate, I do have a decent understanding of this and I'm willing to give it a shot.

    As I understand you guys have done a decent amount of researching companies, do you have any recommendations on who to order ten 150mm ccfl tubes from? I have seen several different lengths of premade straight ccfl, but not 150mm. I suspect it will be cheaper if I don't have to ask somebody to make a custom length for me.

    I almost forgot for a second time - Are you sure about the power requirements for the W-shaped ccfl tubes? (assuming the two ccfls mentioned above are still the W ones) I ask because the 5-6ma that was requested is closer to what I would expect for one tube rather than two.

  2. #572
    MySQL Error Scouse Monkey's Avatar
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    As far as I am aware you can't connect CCFLs is parrallel.

  3. #573
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    Quote Originally Posted by numbers
    As I understand you guys have done a decent amount of researching companies, do you have any recommendations on who to order ten 150mm ccfl tubes from? I have seen several different lengths of premade straight ccfl, but not 150mm. I suspect it will be cheaper if I don't have to ask somebody to make a custom length for me.
    everywhere we get stuff from has a minimum order of 200 tubes, although we have managed to get sample quantities but it costs about $45 for the wire transfer and $50 for shipping! That's a big problem!

  4. #574
    Variable Bitrate numbers's Avatar
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    Anyway, the 150mm tubes would be connected in parallel with a twist. Rather than run a wire from each output on the inverter to each tube, you would have one wire coming from the inverter and connecting to the same side on all tubes, and another wire coming from the inverter connecting to a capacitor soldered to the other side of each tube.
    Without going into why you can't run them in a normal parellel configuration, I will say that doing it this way works around that issue. Doing it this way will light the ccfls. The only thing I don't know about is something along the lines of the tubes having different intensities due to not having their own regulated output (this is a common issue) and the difference in capacitance on the long wire powering them all. (this is a unique potential issue due to this particular setup)

  5. #575
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    Quote Originally Posted by numbers
    Without going into why you can't run them in a normal parellel configuration, I will say that doing it this way works around that issue. Doing it this way will light the ccfls. The only thing I don't know about is something along the lines of the tubes having different intensities due to not having their own regulated output (this is a common issue) and the difference in capacitance on the long wire powering them all. (this is a unique potential issue due to this particular setup)
    yup that is a problem. also a problem with using multiple inverters as wellas the messy wiring of lots of tubes. There is not much room inside the backlight module or around the screen in the case.

  6. #576
    Variable Bitrate numbers's Avatar
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    Ouch. That's not cool. I have seen other lengths for sale with no special ordering policies. I imagine that's due to them being premade and prestocked. The only length thaey have that would work is 4". I suppose I could use those if I had to, but I'd rather them be closer to just under 6".

  7. #577
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    I have seen 150mm tubes but by the time you accoutn for the electrodes you are down at 135mm and you end up with very uneven light and dark patches.

  8. #578
    Variable Bitrate numbers's Avatar
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    Really? Tell me where! I'm too stubborn to not try this. After messing around with the diffuser sheets and whatnot I honestly don't think that should be a problem. Heck, from what I've seen I seriously think 4" tubes might be perfectly fine.

  9. #579
    Maximum Bitrate MaleBuffy's Avatar
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    numbers, why dont you use this:

    http://www.emanator.demon.co.uk/bigclive/neon.htm

    .....ok I am !

  10. #580
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    Sarcasm?

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