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Toshiba A300 LCD Inverter

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    #1

    Toshiba A300 LCD Inverter

    Hi, I'm trying to get backlight working on Toshiba A300 laptop. Basically the laptop comes on but no backlight on LCD screen. I have tried two screens and few spare CCFL tubes that I'm sure works. Also tried three spare inverter boards and they don't seem to do anything. However I have tried using the LCD to LED converter strip to connect and power a 15.6" LED screen and it works and the backlight coming on.

    I wanted to test the voltages on the inverter input connector which is 4 pin connector. I'm getting 19.65V on first pin, second pin has 3.27V (this one is varying a randomly), third pin has no voltage and fourth pin is ground.

    Let me know what could be the issue. Can't seem to confirm if the voltages are correct (tried google images but no luck). Thanks.
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    #2
    Re: Toshiba A300 LCD Inverter

    Hi
    bad lvds cable or light control (kbc maybe)

    try to shunt pin 2 and 3 (best practice is to remove inverter ,shunt then place back, dont make crazy kamikaze shunt on there because sometimes goes very very wrong).

    feedback because i have some working A300 mbs that i can trace back inverter circuit to help

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      #3
      Re: Toshiba A300 LCD Inverter

      Hi, thanks for the response. So what voltage value should be, especially on third pin? I tried tracing the continuity of third pin of inverter connector to the LVDS connector using multimeter but couldn't find it. I had one spare cable but I lost it.

      While I find the correct pin number on LVDS connector it would be nice of you to tell me which pin number on the LVDS connector on the motherboard it corresponds to. Thanks
      Last edited by FShahid; 10-23-2015, 04:01 PM.

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        #4
        Re: Toshiba A300 LCD Inverter

        Hi , you need to have around 3v , 2 and 3 are light on other is pwm for brightness , assuming the 2 that you have is brightness shunt and see if works

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          #5
          Re: Toshiba A300 LCD Inverter

          Thanks rs232killer, that works. After shorting pin 2 and 3 and powering on laptop the backlight stays on and fine. Should I keep it shorted now? I don't mind brightness setting as long as it works. Thanks again!

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