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820-00875 no 20V PPDCIN_G3H flickering

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  • 820-00875 no 20V PPDCIN_G3H flickering

    Hello,

    I have this board which wont turn on. When plugging in the USB C charger I get a current draw of about 20mA. I don't have PPBUS_G3H voltage. My best clue so far is that when I measure PPDCIN_G3H I get around 5.2 volts and occasionally, perhaps as the board tries to turn on, it dips down to around 4.7 and then goes back to 5.2v. I discovered that if i disconnect R7020 the flickering goes away and the 5.2V stays stable. I tried replacing U7000 with no change. I also removed Q7030 and Q7040 and L7030 to try and isolate the issue with no change, same goes for F7000, symptoms stay the same. it seems the only thing that makes it go away is to either remove U700 or R7020. I have PP3V3_G3H but this too dips down for a second from 3.4V to 2.99V. Can't detect any shorts around U7000.

    During my work the symptom has changed a little. Initially when plugging into port A my ammeter would totally shut off for a second as if the PS was protecting itself then go back to normal. If I plugged in to Port B it would stay on but would still not give me 20V and the flickering voltage was still there. I removed the USB C controller for port A to see if this was the issue but it wasn't. Currently this IC is still out of the board and I'm not sure if it's totally necessary for the board to boot. During my inspection of this area, heating around the USB C controllers I got 20V when the board was hot but didnt get to measure how much of the board actually turned on. I can't repeat this anymore unfortunately.

    Am new to this board and am not entirely sure what to look for next on this one.
    Last edited by MexicoTV; 07-08-2019, 08:14 PM.

  • #2
    You MUST have both CD3215s on the board or it will not do anything. You likely have a bad CD3215 pulling DC-In and 3v3 down. Replace both with the correct firmware chip and report results.

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    • #3
      If you got 20V after applying heat to the board, looks like corrosion issue on USB-C area.
      First of all be sure to have both CD3215 good and soldered on the board.
      Be aware of termination code!

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