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  1. #1
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    820-3332 shuts down after 3 seconds and restarts

    This one has had a repair attempted on U8900, but after that it stopped turning on. Also there were two capacitors knocked off the board (C8927 and C8923), which I replaced.
    I reflowed U8900, but there was no power. So I then found a short on PP3V3_S0 which was traced to U9150 but magically disappeared when I reflowed it.

    Now I get power on, all voltages seem present, also CPU Vcore which is 1.1V and then drops to 0.9V, but immediately after it drops to 0.9V, it powers off, then after 2 seconds it powers on again.

    Next, I replaced U9150 from a donor. I also put a new U8900 on just for the kicks (it was outputting proper voltage with the old one), but situation is still the same.


    I am a bit puzzled, looks like it tries to POST or perhaps it POSTs then it detects something is not alright and it shuts down.

  2. #2
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    Re: 820-3332 shuts down after 3 seconds and restarts

    S0 rail shorts?

  3. #3
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    Re: 820-3332 shuts down after 3 seconds and restarts

    Hi, no S0 shorts.
    I think the board actually tries to boot as the CPU Vcore drops from 1.1V to 0.9V.
    I examined the board under microscope and found no problems or knocked off components...

    Any ideas?

  4. #4
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    Re: 820-3332 shuts down after 3 seconds and restarts

    i'd go back over the solder joints of the u8900 with a soldering iron because alot of times the hot air just doesn't do the job

  5. #5
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    Re: 820-3332 shuts down after 3 seconds and restarts

    I always remove U8900 and clean the pads and retin them with leaded solder, then put the U8900 back.
    Of course, I go around the soldering iron a few times to make sure all the pins are nicely soldered.

    I get 0.90V on PPVCORE_S0_GFX when trying to boot.

 

 

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