Laptop won't power on--what can be tested w/ digital multimeter?

Discussion in 'Electronics Resources' started by calcitrant, Jun 1, 2011.

  1. calcitrant

    Thread Starter New Member

    Jun 1, 2011
    4
    0
    I've got an HP DV6000 laptop that stopped powering on after being dropped. The A/C adapter and power jack module were damaged due to the fall, so they have been replaced. Unfortunately, the unit it still not powering on.

    My knowledge of laptop disassembly is solid but I have only a working knowledge of electricity and multimeters... so I'm looking for advice as to how I can use a multimeter to troubleshoot electrical issues within the laptop.

    This is the laptop service guide: http://is.gd/i7RHy1

    This is the multimeter http://is.gd/P6Mhnq

    Any guidance at all is greatly appreciated. :)
     
  2. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Welcome to AAC.

    A multimeter is not much use in pc servicing.

    You said that the power jack has been replaced. This is a significant task with most laptops as you have to remove the motherboard to do this. Further the board may be layered so soldering is difficult.

    More importantly you need to be more detailed and more specific in your information.

    You say the original fault arose as a result of a fall?

    How di the laptop perform immediately before and after?
    Was the screen itself damaged?
    Was there any output onto an external screen?
    Do any of the tell tale lights come on?
     
  3. calcitrant

    Thread Starter New Member

    Jun 1, 2011
    4
    0
    Thanks!

    Correct; I replaced the entire power jack module--no soldering required. I used an ESD wrist strap during this process and did not see any signs of damage beyond the power jack.

    The laptop was powered up, it fell on the power jack and turned off abruptly. The laptop is now unresponsive, indicating that additional components may have been damaged, presumably due to a surge (I do not suspect any issues with the LCD, inverter or GPU).

    What I hope to figure out is where I can apply multimeter probes to identify breakdown in current beyond the power jack.
     
  4. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Whilst dropping your laptop onto a corner is a nerve racking experience it does not usually result in total destruction.

    That was why I asked very specific questions (I do do this for a living) which require very specific answers.

    The most likely damage will have been caused to the 'light bulb' - sorry CFL lamp - behind the screen.

    But to test this you need to answer my earlier questions accurately.
     
  5. calcitrant

    Thread Starter New Member

    Jun 1, 2011
    4
    0
    The CCFL is physically fine to the best of my knowledge but even if damaged, shouldn't prevent the laptop from powering on. Right?

    To answer your previous questions, the laptop functioned normally before the fall, and would not power on after. The screen is not damaged--the only damage occurred to the power jack and A/C adapter. External video output cannot be tested as the unit will not power on. Ditto for LEDs.
     
  6. calcitrant

    Thread Starter New Member

    Jun 1, 2011
    4
    0
    I was able to answer my own question, so I figured I'd share the answer.

    To use a multimeter during laptop testing, the multimeter should be set to read voltage measurements.

    I won't go into A/C Adapter testing as this has been covered quite thoroughly elsewhere.

    Regarding daughterboards, however, the 'positive' lead will be placed on a solder pin underneath the PCB being tested while the 'negative' lead will be placed on a ground trace around a retaining screw on top of the PCB being tested.

    For the most part, any daughterboard can be tested in this fashion to trace an electrical breakdown.

    Cheers!
     
  7. studiot

    AAC Fanatic!

    Nov 9, 2007
    5,005
    513
    Well done!

    :D
     
  8. artofkicking

    New Member

    Jun 5, 2011
    4
    0
    You said it fell on the power jack.
    I am guessing it was plugged in at the time. I would look for damage to the board solder connections by the plug first. Most laptops can handle a little shock as the are UL listed and are dropped as part of the testing process. You may have just loosened a "cold solder joint" . There are not always easy to spot but if there is a bad solder spot it will most likely be VERY close the where you cord plugs in..
     
Loading...