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Dell Precision 5530 15" died to blown chip. Replaced chip and now only get momentary fans, lights, no screen or boot

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    #1

    Dell Precision 5530 15" died to blown chip. Replaced chip and now only get momentary fans, lights, no screen or boot

    Hello,

    My Dell Precision 5530 turned off suddenly when I was running Matlab and wouldn't turn on, show any lights, fans, and/or any signs of activity at all. I opened the case, removed the battery and looked at the board with a thermal camera while the AC adapter was connected. I saw that PU1252 was >120C so figured the chip had died on me Got the part number off the attached schematic (see Mouser link below) and replaced the chip. After replacing the chip the board (connected to AC adapter) was able to briefly power on, spin the fans a little bit, and turn on the front led lights. However, after turning on for about 1 second it then shuts off. Also looked at it again with the thermal camera and nothing is getting hot now.

    Have a good amount of hardware experience but not so much computer architecture and which voltages need to be what in order for things to work correctly. Took the measurements below so far, but can take whatever other measurement you think would be useful.

    When I say "briefly" I mean that voltage reads 0V until I press the power button and then the voltage appears briefly before dropping back to 0V when the computer turns off. Resistances obviously measured with power disconnected

    Thanks for any help

    B+ 13.52V
    VALW 1.053V (briefly)
    1.2V_DDR 1.195V (briefly)
    1V_PCH 1.053V (constant)

    GPU_Core 1.8 Ohm to Ground
    0.8V (briefly)

    VCC Core 3.2 Ohm to ground
    1.05 V (briefly)

    1.8_PCH 1.86V
    1.8_PCH_LDO 0.63v (Resistor rh5880 not populated)
    1V_PCH_PRIM 1.053V

    https://www.mouser.com/ProductDetail...6VEJNV1A%3D%3D
    Attached Files
    Tags: None
    #2
    Hi. Suggest to read the sticky above on charger circuits by piernov. Then carefully check the voltage to ground of the DCin mosfets.

    being a Dell product, the single wire ADAP_ID is critical. Check the voltage to ground of this line. Without proper adapter ID detection will fail.

    Comment

      #3
      Went back and traced through some of the charger circuit. Saw 19V on DC_IN but not on SDC_IN or DC_IN_SS. Could be reading this schematic wrong, but doesn't it seem like I am missing this 0ohm resistor to PQ205 gate that pulls down the PQ200 gate and turns S1 on?
      Attached Files

      Comment

        #4
        The missing 0 ohm resistor could now be just a pcb trace to save on cost. Check with no power and meter in resistance mode. Measure the resistance from the logic gate to this mosfet gate pin.

        Comment

          #5
          PU1252 is a dual n channel mosfet i beleive(not looked into schematic/bv) and if it was shorted,there is high chances that cpu got damaged.

          PS: I dont see any merit in troubleshooting charging section as almost all major rails are rising which is a proof enough that B+ is generated correctly.

          Comment

            #6
            You were right about the missing 0 ohm and the pads measure short across.

            I am no longer getting fan spin or lights when I hit the power button and +B is 1.6V now (instead of 13.5). If the CPU was damaged and dying I could see trying to repeatably restart the computer finally cause it to kick the bucket. Not sure where to go from here.

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