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820-00281 No PPDC_IN

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  • 820-00281 No PPDC_IN

    Board has no signs of liquid damage. Came in with dead battery and no power. When I plug in adapter I get .4## Volts on PPDCIN_G3H. Also QB400 gets very hot and after about 30 seconds the charger cuts off.
    I only have the center portion of a donor for this board as I could not find the right side on ALI. I did however order FDPC4044's from mouser and new ISL's as well in hopes that those would be the issue. After replacing QB400 I still get basically nothing on PPDCIN_GH and QB400 is scorching hot.
    I have zero experience with this board and to be honest am a bit intimidated, LOL. Here is what I get on he power meter. ------------>

    Any help is appreciated. Thanks!

  • #2
    Post resistance to ground on R7020 and F7000.

    Don't wait again 30s when you already detect overhrating.
    In fact, never power up a board before check for shorts...


    • #3
      Resistance to ground on PP3v3_G3H and DC in? Seems like you have a short causing the fet to get hot possibly a CD3215


      • #4

        12.89k on pin F7000
        .428 Diode

        .7 Ohm on pin 1/2 of r7020

        Thank you


        • #5


          3.16k on PP3V3_G3H

          1.2 Ohm on DCIN


          • #6
            Ok so DC in is shorted to ground. Inject voltage on that line and see what heats up.


            • #7
              OK. Thats a 20 V line. What voltage do you think I should start at? Thanks.


              • #8
                Don't think to start with 20V.
                Always start with low voltage, no matters nominal voltage of the rail.
                If you start with 1V, increase voltage maintaining ampers bellow current limit of the bench power supply.


                • #9
                  Yeah I'd say start low around 3-4 volts then work your way up. For me, the DC in shorts usually are found at 5 volts so 20 is probably not necessary.


                  • #10
                    trying to inject 3.5V on DCIN line. Here are 2 pics. One is with PSU set for voltage injection at 3.5 and the other is while attempting injection. Amperage goes up to 3.9 and board will only take .7 V.


                    I did not force by raising the amps/voltage once I saw that the board wasn't taking it.

                    Is this a secondary short? What should I do?

                    Thanks for the help. Have a good one!
                    Last edited by Ryanlen2; 12-19-2018, 05:54 PM.


                    • #11
                      Set current limit to max for becnh power supply.
                      Then start injecting from 1V and go up...


                      • #12
                        Ok, thank you. Will post back in AM. Thanks again.


                        • #13
                          After injecting voltage I found C7029 to be sizzling at 3.5 V. Replaced the cap and all is great!

                          Thanks a lot 2informaticos & JohnB8812 for all your help. I appreciate your guidance.

                          Have a great one.


                          • #14
                            Good job! Glad we could help


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