820-02100 No keyboard or trackpad, screen flickering

I have a 2021 16" 820-02100 board that is liquid damaged. It only had some light corrosion around UD102 area and pin 32 on the keyboard connector, which was for PP3V3_AON_KBD_CONN. I cleaned the corrosion and replaced some resistors and caps. The mac turns on and makes the chime nosie and I can see the apple logo on the screen, but no backlight on the screen. Then the image goes away completely and it just stays like that, until I press the power button once. Then the screen turns on with image and backlight now, and shows the login screen, but keyboard and trackpad do not work. Also, the screen keeps flickering on and off randomly. I checked the board outside of the case with only the charger and trackpad connected and it appears I am missing PP3V3_S2_IPD. This comes from UT390, and I have 3.8v on PP3V8_IPDLDO_VIN and 1.75v on IPD_P3V3_PWR_EN_RC, so the chip is being powered and told to turn on, but no output. PP3V3_S2_IPD is .411 in diode mode, so no short. I replaced UT390, but still have 0v on PP3V3_S2_IPD, and I do not know why. Any ideas?

IPD_P3V3_PWR_EN_RC - 1.75v
PP3V3_S2_IPD - 0v
PP1V85_S2_IPD - 1.85v
PP1V2_S2 - 1.2v
IPD_LID_OPEN_1V8 - 1.8v
PP5V_S2_TPAD_CONN - 5.0v


Staff member
I don't see other reason than bad UT390, or overload on its output; considering is soldered correctly.
Check its voltages with JT400 disconnected.
Yea its still 0v without the trackpad connected. I do not have anymore TLV70733PDQN chips to replace UT390 with. Can I use another chip, like the NCP160AMX180 from older boards?


Staff member
Use it, if has the same size and pin layout.
Be sure to have the same output voltage.
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I got another TLV70733PDQN and replaced UT390. Now I got 3.3v on PP3V3_S2_IPD, but the keyboard and trackpad still did not work. The trackpad does not even click, so it seemed like its not getting power at all. I checked all the traces and they seemed fine, so I suspected the trackpad was bad. Got a new trackpad and tested it, but still had the same issue. It ended up being a faulty lid angle sensor on the screen that was causing all these issues. I replaced the lid angle sensor and everything is working fine now.