A2338 820-02020 5v 0.07 not turning on

[Extreme]

Hello, I have received a Macbook Pro with no power.

The device was affected by water damage, I fixed all the corrosion found, but it is still the same.
The voltage is 5v and 0.05a to 0.08a slowly fluctuating.

PPBUS_AON is stable
3V8_AON is 0.200V going to 0.400V.
LC320 in diode mode is 0.009, is normal or short?

Is any help that I can get to finish the issue quicker?


Thanks in advance.

 

[2informaticos]

I don't have a board for comparison, but such reading is very low for 5V_S2 power line.
You can try injecting voltage and check if something heats.

 

[Extreme]

I have injected 2v on LC320 and UP700 is getting hot.

 

[2informaticos]

Remove it and check again in diode mode.
Check on its output too (5V_SW_LCD).

 

[Extreme]

I took out the UP700, and measured all the lines, but EDP_BLC_5V_EN is shorted to the ground. UP710 might be faulty?

 

[Extreme]

Yes, confirmed the SLG4AP43605V( UP710 ) is shorted to ground. Now the issue is that I am unable to find this ic.
Any hint?

 

[2informaticos]

Need scrap board probably...

 

[Extreme]

I have removed the short, and the MacBook is turning on, but now I get full fan spin and no backlight or touch bar on.
Any help would be appreciated.

 

[2informaticos]

Do you get image, only missing backlight on internal LCD?
Did you check UP710 signals?

 

[Extreme]

I get image, but no backlight. I have replaced the backlight driver but is same. I will check the signals as well shortly.

 

[Extreme]

UP710 from the schematics I see that is enabling the display, which is working; I went to UP800 is not giving any voltage on LCDBKLT_SW, this was replaced.
QP800 I have 11.5V on pin 3 and 11.9 on pin 4.
I am quite confused as I can't spot any other short or any reason why UP800 is not producing voltage for LCDBKLT_SW.
Touchbar and backlight are both not working,

Sorry if this sound awkward, but I never worked on these motherboards before.

 

[2informaticos]

I don't know what kind of voltage do you expect on LCDBKLT_SW.
There is not what you think!

QP800 needs low voltage on Gate.
For this, UP800 must pull down BKLT_SD (0V).

Apart of BKLT_EN_R (high), UP800 requires a good communication with LCD assembly (T-CON), through I2C bus (I2C_BKLT_SCL/SDA).
M1 sends backlight adjust command to T-CON via SPI bus, not directly to UP800.

I recommend you to test with known good LCD assembly.
Just in case, check diode mode to ground on both pins of DP800; w/ and w/o LCD connected.

 

[Extreme]

All right, My apologies; I should have checked with a new screen. I found a broken screen but showing backlight.
It Is amazing how the components communicate with each other.
I kept thinking was a board issue.

Thanks for everything.