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Acer Aspire 5738G - no POST

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    Acer Aspire 5738G - no POST

    Hi,

    I have a laptop which has stopped working and thought this might be the best place to get some guidance as to where to look next.

    Acer Aspire 5738G (ATI HD4570 graphics)
    Winstron
    JV50-MV M92 MB
    48.4CG07.011

    Some background: Laptop was bought new back in 2009, battery died a couple of years back so been used on mains only. Was having overheating problems where it would shut itself off every so often - usually when on the bed etc. Because it was on mains only I was in the habit of closing the lid and pulling the power cord out. Had been using it the night before it stopped working and had done just that.

    The laptop now doesn't want to post.
    - Power LED's come on
    - Nothing at all on screen
    - Power switch is working
    - Fan comes on, then stops, seems to come on again as the laptop heats up
    - Can hear the HDD spin up, heads move once, then just sits there spinning (HDD works fine in a USB caddy)
    - The southbridge does seem to get quite warm after a while - this might be normal though?

    I've tried the BIOS emergency recovery but got no response.

    I've checked quite a few of the power rails and they seem ok, 5V_S0 and 3V3_S0 come on/off with the power button as expected.

    With the main board by itself, all drives, display etc removed I'm getting:
    0.02A @19.0V (first application of power)
    1.17A @19.0V (power button has been pressed, fan has stopped spinning)

    I put a logic analyser on the BIOS chip and I'm seeing data on both the input and output. No idea if it's valid and my analyser can only sample at 24MHz.

    Due to the overheating and after reading quite a few other posts in these forums I suspect I might be looking at a bad BGA joint, but would appreciate if anyone else has any guidance on where to look to help narrow down the issue. I am looking to buy a new laptop - primarily use my desktop, but would like to track down the issue just out of interest.


    Thanks.

    #2
    Re: Acer Aspire 5738G - no POST

    Try to reflow GPU for 20sec at 260-280C.

    Comment


      #3
      Re: Acer Aspire 5738G - no POST

      Originally posted by PlusCom View Post
      Try to reflow GPU for 20sec at 260-280C.
      Yep, that was the problem.

      Used some tinfoil to mask the graphics chip, thermocouple attachment for my DMM to monitor the temps (sat it on top of the die) and my heatshrink gun (Proxxon MH550) to reflow. Probably done it for around 1 minute since the temperature took a little while to come up. Plugged the LCD in (with just the RAM) and now get POST with no OS found etc displayed.

      In case it helps anyone, with only the RAM in the board I can now clearly see the bench power supply current fluctuating up/down for a while when the power button is pressed whereas it was previously sitting steady. Now settles at roughly 1.60A (front panel reading).

      Now to find all the screws and reassemble...

      Comment


        #4
        Re: Acer Aspire 5738G - no POST

        No...now you need to replace that chip because the problem will return to you very soon.

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