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Seeking help reverse engineering laptop screen inverter sans datasheet

Discussion in 'Troubleshooting and Repair' started by seanspotatobusiness, May 21, 2017.

  1. seanspotatobusiness

    seanspotatobusiness

    190
    4
    Sep 11, 2012
    I have a few inverters from broken laptop screens (Dell Latitude LS model) and there are no datasheets that I can find for the controller IC (3972 OAW). There are only four input pins for the inverter board and I think that it might be possible to figure enough out to connect it to power without breaking it and then experiment to turn it on.

    I've found what I believe is the ground pin because it's connected to that big metal area of the board that the screw goes through into the laptop chassis.

    What is the most likely candidate for VCC? Pink is connected to the coils and to a giant SMD-capacitor looking thing which can't be a capacitor because it's two terminals are shorted and that's probably not a fault because it's the same on the other boards. But the pink seems to go backwards through a diode (D2) so maybe it can't be VCC?

    The other two pins must be the ON/OFF or STDBY and the DIM pins but I think it will be possible to just apply 3 V to either and see what works?

    I think I can apply, like, 12 V to the power pins and different combinations of 3 V and 0 V to the other two, right?

    (Of course I will take measures not to shock myself)

    [​IMG]
     
  2. seanspotatobusiness

    seanspotatobusiness

    190
    4
    Sep 11, 2012
    Does this image make it any clearer what candidates may be VCC and GND?

    [​IMG]
     
  3. seanspotatobusiness

    seanspotatobusiness

    190
    4
    Sep 11, 2012
    Okay, as I suspected black is GND and pink is VCC (I used 12 V).

    Blue is ENABLE and needs 2-6 V to come on and yellow is DIM (0 V is max brightness and increasing towards 2 V causes the CCFL to dim and eventually flicker erratically; I'll be tying it to ground).
     
  4. seanspotatobusiness

    seanspotatobusiness

    190
    4
    Sep 11, 2012
    Correction: ENABLE pin can be left disconnected because it's tied to VCC somewhere therefore on by default.
     
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