Help with Macbook Pro A2338 no power and no display needed

[dbuergi]

Hi all

i have a 2338 which had no display (there is a little crack near the edge to the case) but worked with external display. Some weeks later it didn`t boot anymore.
USB Tester shows 5,18v, 0,08 a and 0,38w with power supply.
With battery connected i get 20v and 0,0 a
Thermal camera shows that U0500 is heating up to 30c.

F5200 is not shorted
Visual inspection didn't show any problems.

I'm sure that i need to change the display but what can i do to find my other problem with the board?

[mon2]

Study this webpage on how the 20v power delivery contract is selected:

https://logi.wiki/index.php/CD3215_Bootup_Sequence

Be sure the BMC power rail is present on each port that is active with the power adapter. Do also test the opposite side of each port by rotating the connector by 180 degrees.

[dbuergi]

Okay, looks like i should add some more details. Board is 820-02020A
Checked all fuses now and no shortage.
C5250 shows 12,34v and nothing susicious on second power line. I tried to find this problem with google and got a thread where M1 chip was dead. Is this a possibilty and "fast" way to find it out?

What i didn't try until now is DFU recovery. As stated in other posts i`m new to Apple and don`t know if this makes sense in this case.

[mon2]

Is the voltage @ C5250 stable or power cycling?

Issue may be that you require the DFU.

MacBook Pro A2338 Not turning on, 0.00 - 0.05A current draw at 5V repair - Repair Wiki

Update:

U0500 - any liquid damage to this region? Apply alcohol and clean up this device area if you suspect any liquid spills. 30C is not too high for an IC.

[dbuergi]

No liquid spills and everything looks dry and clean. C5150 is stable.
So tomorrow i will try DFU recovery.

[dbuergi]

I tried several times to enter DFU mode without any success so maybe i missed something else. :-/

[mon2]

The board is not at 20V so this usually means the ACE controllers (power delivery CD321x) are suspects. Check the LDO rail of each such controller.

Carefully measure the voltage to ground of:

I2C_SMC_PWR_3V3_SCL ; at battery connector J5151 (TP5103)
I2C_SMC_PWR_3V3_SDA ; TP5104

[dbuergi]

I2C_SMC_PWR_3V3_SCL is 3,261v
2C_SMC_PWR_3V3_SDA is 3,260v

Checking CD3217 showed
PP5v_S2 on LC320is 0,006v
PP3v3_S2_UPC is 3,3v
PP1v25_S2 is 1,226v

All is present. So if i understand it right there can be a problem with UF400 and UF500?

[mon2]

The LDO rails on the CD321x must be present for the IC that is mating with the usb cable. That is the active port and the PD controller should create each required power rail. If one PD controller fails then you will not reach the 20v contract.

[dbuergi]

Thank you! So maybe another stupid question but can i find out which IC ist causing the problems or should both be replaced?
Im not at my desk so i don't know the name of the points i checked near the ICs but at both ICs i get 3,3 and 1,5v. If this isnt any help i will give more details later.

[mon2]

Study this webpage on how the 20v power delivery contract is selected:

https://logi.wiki/index.php/CD3215_Bootup_Sequence

Be sure the BMC power rail is present on each port that is active with the power adapter. Do also test the opposite side of each port by rotating the connector by 180 degrees.

[dbuergi]

I checked both sides and everything looks the same.
One thing i found is PP3v3_S2_UPC having 3,3v but in diode mode i get 1,6v without power supply attached.
Sorry if i get something wrong or it takes longer to understand but reading all this stuff not in my mother language is way harder than i thought.

[dbuergi]

So once again i'm looking at this board and i guess i made a mistake.
With power supply connected i get 0.070A and it goes up to 0.078 and back down and up. So is this already power cycling?
If so i also get different measurements when testing output of U8100 and U8100.

Diode mode:

PPVDD_PCPU_AWAKE 0,038v
PPVDD_ECPU_AWAKE 0,47v
PPVDD_CPU_SRAM_AWAKE 0,6v
PPVDD_SOC_S1 0,37
PPVDD_GPU_AWAKE 0,034v
PPVDD_DISP_S1 0,091v
PPVDD_DCS_S1 0,46v
PP1v4_LDO_PREREG 1,36v

Resistance is too low on all points. As example PP1v4_LDO_PREREG 3,8k Ohm.

[dbuergi]

I made one more finding. CF031 and CF051 Look corroded.

[dbuergi]

Hello again,

im sitting at this board again and this should be the main problem. UF710 is looking the way shown in the pictures and RF713 is missing.
Right now i don`t have a donor board, so anything i can do without it? Only spare around is a A1466 board.