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Laptop Charging problems

Discussion in 'Electronic Basics' started by Fantastic Dan, Sep 9, 2003.

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  1. I recently bought a car adaptor for my HP N5420L Laptop so I could use
    my laptop on the road. When I plugged the adaptor into my cigerette
    lighter, the LED on the actual charger did not light. I double checked
    my ploarity and it was correct but still no change. Then I tried
    switching the ploarity to see if it would have any effect, no change.
    So I just figured the adaptor was faulty. However when I returned home
    and plugged the laptop into the wall adaptor, the LED on the AC/DC
    converter flashed dimmely and the laptop did not recognize a charge.
    When I unplugged the charger from the laptop, the LED on the AC/DC box
    lit up like normal... I'm getting quite worried that I may have some
    sort of serious problem here. I haven't contacted HP yet, I figured I
    would see if anyone knew if there was some type of simple fix or
    anything for it.

    Thanks in advance!

    If you want to email responces, my email is , not
    the one listed here.
  2. This should have been the point where you stopped. If the charger does not
    light in the first place, there is clearly something wrong.
    *Polarity*. Did you by chance plug your laptop into this thing at this
    If you plugged the car adaptor into your laptop at some point, and
    particularly after you reversed the polarity, it is very likely that you blasted
    the circuitry inside the laptop. Probably only the charger circuitry, but
    something has been damaged.
    If the charger was not an HP charger, you have murdered your warranty once
    and for all. HP can be very snooty about this sort of thing, but now you
    probably have unhappily found out why. No simple fixes for this; laptops are
    cramped and often have very specialized components inside.
    The power supplies often use very late model (or custom) switcher chips and
    in any case are almost completely surface mounted these days. Even a good tech
    will have a tough time. Your best bet is to plead ignorance to them, claim you
    never used a car adapter, never knew such a beast existed, whatever. Let your
    conscience be your guide.


    Chip Shults
    My robotics, space and CGI web page -
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