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    Repairing Today

    Discussion in 'Hardware Components and Aftermarket Upgrades' started by jialinc, Sep 25, 2008.

  1. jialinc

    jialinc Newbie

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    1. DV1000
    Not power up.
    The current jump from 0 to 0.5A, and it should stay on 0.03A while in S5 mode(S5 is standby mode). There must be some shorts on the board, but couldn't find it by just use multimeter.

    Find the VIN point (common point of external power and battery power), apply a 5V voltage and 1A current try to burn faulty components. I find that Q154, Q155 are very hot. These are 2 N channel mosfet. Replace them with 2 N channel mosfet. The board is not shorted any more but still not power up.

    Measure the V+ (19V), VCC (5V), SHDN (5V), ON3/ON5 (5v), REF (2V) of Max1999 (max1999 is the system PWM chip, all other powers come from here), all the voltages are normal but no output. So change max1999 and system standby voltage 3v on pl9, 5v on pl10 all up.

    Switch on and board power up successfully.

    2. Acer 290
    Power up but will cut the power off before it output any display.

    Power cut off point is around 0.4A, either short on the board or missing one or 2 powers.

    Mearsue powers on north bridge, find only 1.5V, missing 1.05V and 2.5V.
    Trace the circuit from north bridge back to PU20, PU21 (CM8562), those 2 supply the 1.05V and 2.5V to north bridge. Find no powers go into these 2 chips. Trace to PU23 (FDS 5234Q), which is dc-dc converter supply power to PU20, PU21. Replace PU23 and board working perfectly.

    Most components I mention in here have datasheets in
    www.alldatasheet.com
     
    jialinc, Sep 25, 2008
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  2. miketford

    miketford Newbie

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    You seem to have a lot of information about laptop motherboards. Any chance you have a schematic for an HP Pavilion N5445 MB you would share? Thanks.
     
    miketford, Jan 31, 2009
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