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HP-Compaq HP 6720S starts with black screen

Discussion in 'BIOS Laptop' started by mohkamtech, Feb 28, 2015.

  1. mohkamtech

    mohkamtech Well-Known Member

    Feb 25, 2015
    Likes Received:
    Hi members,

    Hp 6720s- platform: DDD UMA 6050A2137901-MB-A03

    When started, fan spins continuously but no display on screen and external monitor.

    Current reading : 0.003-0.48 and stopped at 0.68

    Steps made :

    Replaced ram, and cpu, with known good working ones, same problem.
    Flashed bios, reflowed GPU for test purpose to no avail.

    Tested mobo :
    -CPU voltages :
    Vcc_Core :+1.12V
    VCCP : +1.18V
    +V1.5S : +1.7V a little high
    H_Pwrgd : +1.18V
    H_Cpurst# :+ 1.8V

    GPU voltages : +1.18V; +1.44V; +2.08V

    All other voltages are present and measured good except :

    -At CN17 (lvds connector) :
    +V3A(pins 18-19-20) is missing due to "LVDS_VDD_EN" absent.
    LVDSA_DATA pins signals are also absent.

    -Bios (soic8) pins 1 and 2 always 3.54v strange !!!

    Please advise as where to dig further ! Bios, I/O or other component
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