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820-00281 2.2V on PP3V3_G3H

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  • 820-00281 2.2V on PP3V3_G3H

    Client brought in device after device was liquid damaged. Noticed a build up of corrosion around U6903 which appears to be where PP3V3_G3H is created, and a blown Diode D6902.

    First thing I did was give device an ultrasonic cleaning to remove the corrosion to get a better look. After which, I replaced D6902 since it was severely blown. Images of before and after cleaning attached below. Device still would not boot, so I then applied alcohol around there area and injected 3V using a DCPS on to D6902 and discovered that C6906 was shorted. I have removed and replaced the shorted C6906, however device still does not boot.

    U7000 is sending 5V to PM_EN_P3V3_G3H to Pin 10 on U6903. (Is this voltage too high?)
    Pin 2 on U6903 is being supplied 4.2V from D6902, however D6902 is being supplied 5.2V on PPDCIN_G3H.
    I believe U6903 is bad and is pulling down voltage.
    Pin 9 on U6903 P3V3G3H_FB is outputting 0.66V,
    Pin 3 on U6903 P3V3G3H_LX Is outputting 2.2V.

    USB-C Ammeter reads 5.2V with .0A consumption. I applied some more alcohol around U6903 and injected 3V on PP3V3_G3H with a .05A Consumption. I am currently waiting for some replacement CD3215 to arrive, but until then, any suggestions on what else I should be looking for? If U6903 truly is bad, I found some replacements on DigiKey.com

    Thank you in advance!
    Attached Files

  • #2
    Do not put the board in UC to clean so small area.
    Scratch with fine tip and fiber glass pen.
    Then clean with IPA and tootbrush.

    I suppose corroded components around U6903.
    Pay atention to R6910/11/12/13.
    Also be sure R6908 and C6907 are both OK.
    Check traces and solders too.
    If all OK, change U6903.

    Comment


    • EsteTron
      EsteTron commented
      Editing a comment
      Thank you for your input. I will make note of the UC for the future. The other components you mentioned test out fine, so it looks like I will be ordering a replacement U6903. Is it okay for the enable pin on U6903 to be 5v? I just want to make sure U7000 isn't sending too high of a signal. Thank you.

  • #3
    Yeah seeing where the corrosion was on this one, I don' think CD3215 issue even tho it is possible. Best for you to order some donors and replace what is nasty especially U6903.

    Comment


    • #4
      It took a while to get back to this board, however I did receive replacement U6903 chips. After replacing the chip, the board still get 2.2v. However, if I remove R6923 at the end of this circuit, the circuit gets 3.4v on Pin 1 of R6923. My thought process is that there is something pulling down voltage on Pin 2 of R6923. I then injected 3.3v into Pin 2 of R6923 which pulled at .015Amps and measured with Multi meter around all CD3215 which all received 3.3v. I am now stumped and do not know where I should be looking.

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      • #5
        Is R6923 ok?? Did you replace any of the corroded components near U6903? My thoughts are something is definitely pulling down your 3v3 line like you said possibly a CD3215 chip OR seeing where your liquid was it could even be the ISL9239. Voltage present at pin 10 of U6903 with a good R6923 on the board?

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        • #6
          I removed R6923 from board and measured 0.4 ohms. Schematic says R6923 is 0 ohms. I did replace all corroded components except L6900, I do not have a replacement for this inductor in stock currently. I did replace U7000 just to be sure there was no internal damage. Pin 10 on U6903 is currently receiving 4.9v from with R6923 on board. I just received new stock of CD3215 from Louis's online store recently, but have not replaced them yet.

          Comment


          • #7
            4.9 seems really really high to me.. sounds like possibly bad ISL9239 or improperly soldered ISL9239. Should be approx 3 volts on enable

            Comment


            • #8
              I thought so too when I initially measured U6930. U7000 originally was sending 5V to Pin 10 before I replaced it. Perhaps something around U7000 is putting out too much power throughout this chip.

              Comment


              • #9
                Just to rule out that there was not any internal issues with CD3215, I went ahead a replaced all 4. Board is still getting 2.2V on PP3V3_G3H. I then removed U7000 again and hooked up USB-C power supply and discovered that with U7000 removed, the enable Pin 10 on U6903 receives 1.5v. From my understanding, it should be 0v with U7000 removed. I think some extra power is somehow in my enable line. I am looking in to this line currently.

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