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Checked again, it's stable. I plug the charger in, it switches to 20v and from this moment CPU VCORE goes up to 0,959v and stays like this. I kept measuring it for 1 minute, it's not changing at all.

I have checked continuity of traces between J4500 and J4501, they are OK. Also checked resistors and traces from J4501. I've reflowed SMC with no effect. I have no idea what else I can do.. Computer even can't be used with keyboard disconnected because it won't have working fans.

PPVCCCPU_S0G is stable 0,959v and CPU gets warm.

@2informaticos today my donor boards got delivered, I've changed SMC along with U1900 and the results are: it turns on 20v right after I connect charger (previously I had to wait a while), but it's stuck at 0,45A. Also, what's good news I already have steady 13v on PPBUS. After connecting...

Replacing SMC solved the problem, computer works stable for few days already. @2informaticos thank you for your help and patience! ;)

For 820-2915 remove u9600 and use solution from this photo + remove R8911 after soldering wires. Some say you can leave u9600 but I always remove it. For High Sierra you will also need to make jumper between pin 2 of R9704 and pin 1 of C9711, otherwise after closing and opening the lid there...

You mean it’s 10ohm each or between them? Resistance between pins 27/28 of U7000 should be 20ohm. Are big coils on the board pulsing while quarter fan spin?

I see, thank you for explanation. I will check more carefully J4501 and inspect the areas under it. Also will check continuity of traces between J4500 and J4501. Would you dig into this board or it seems hopeless?

I’ve tried it, no changes. I connect only display and keyboard, board restarts while booting system. Even with everything connected to board except keyboard, it works perfectly. There are KBD_I2C_SDA and KBD_I2C_SCL lines in connector. I wonder, where are they going to/coming from? Between which...

The whole topcase was replaced by Apple. I’ve asked them for details which parts they left there from old topcase and they have replaced everything except board, screws and Touch ID, so trackpad flex and board were replaced too.

This is reading in diode mode. I get constant 3,3volt on this line when board starts, no matter if keyboard is connected or not.

SMC_LSOC_RST_L is always 3,3v, no matter with or without keyboard connected. SMC_ONOFF_L steady 3,4v All voltages on U5256 are present, only SMC_4FINGERS_RST is 0v Keyboard connector is well soldered, on the other side of the boar there are only Q6000/Q6050 with some caps and resistos, they...

Does system recognise new screen now? What does J8500 look like? Any signs of burn? Disconnect charger and battery and check if PPVOUT_S0_LCDBKLT is not shorted. On these screens even if there is an image it's really hard to see it without backlight, even with flashlight. Also check LID_OPEN...

I've replaced SMC and it seems that it was the problem. Except first 2 tries when board didnt react for charger, now after SMC reset it seems OK - turning on, charging and working on battery, loading OS correctly. I will test it today and report if problem has been solved.

Generally try to not mix EFIs or chips from different boards. If it runs with other U6100 but doesn't boot to OS, try to take new clean EFI for your board, put your original fsys info there and check if it will boot up. Don't forget to perform PRAM reset after flashing EFI.

These boards are big waste of time, in most cases it's dead CPU because of overheating or dead SSD's

I have 820-00239 board which is working perfectly only with keyboard flex disconnected. Customer says, that computer was dropped. In most cases when I plug keyboard flex in (J4500) computer starts, shows Apple logo, loads system halfway and shuts down. Sometimes it lets me to write password, I...

I've already done it in beginning of the thread. I'll relpace it this time.

It's pulsing too, gets to 3,3v then drops. But board doesn't pulse every time I connect charger. Sometimes it just doesn't react at all, sometimes it's pulsing. While measuring ALL_SYS_PWRGD on R2584 it turned on twice, behaving like while normal board start - CPU got warm, fan was speeding up...

20v is not only related to CD3215 controllers. Check their LDO's, also check voltages around U7000.