I've done a PMIC replacement once on Rasp pi 3B+ and managed to get it working again. This is the second time I've done a PMIC replacement.
The symptoms are exactly the same, PWR LED on, 3v3 and 1v8 shorted to ground. So I used my already-in-stock MXL7704-R3 to do a PMIC replacement. After replacement, I inserted a working SD card tested on another rasp pi. ACT LED turned on with a 4 slow blink and 7 fast blink sequence, indicating a power failure type B. Unfortunately I can't seem to find anything about power failure type B. Any info on this will be appreciated.
After that, I unplugged the rasp pi and plugged it back in. The 3v3 line is still normal. however, there's no voltage on 1v8. Tested for short and no short on 1v8, so there is no problem with the PMIC.
I want to know what's the cause of this problem as I managed to do a PMIC replacement on another 3B+ with the exact same batch of PMIC.
does it have something to do with the programming of the PMIC?
something to do with the SoC and PMIC I2C communication?
Is it possible to fix it by myself or is it a dead end?
edit: Here are pictures of the rasp pi,
I noticed that there're some missing passive components (3 of them). Are these passive components critical? If so what passive components go there? I'm having a difficult time finding out what components that should go there.
Is the missing passive components the culprit? Any info on what components go there would be valuable. I still want to continue fixing this rasp pi to practice my skills.