820-00281 A1707 TOUCH BAR model . NO BACKLIGHT

[Don Anton]

Hi all,



This is a liquid damaged board but tiny bit near the lcd connector. I check the LCD with working board and LCD by itself is fine. I replaced the LCD flex cable still the same with damaged board.

macbook works fine with external monitor. but with the internal display not sure if this is only backlight or no display as really hard to see the picture on this model LCD's.

I checked backlight circuit.

U8400 get current sensing power 12.66/12.67v on pin 9/10. But EDP_BKLT_EN signal is missing. diod mode its 0.372v.\

BKLT_SD is 12.67v and q8400 not opeing the gate.

Check on J8500 LCD connector . There is 5v on PP5V_S0SW_LCD
on pin 45.

Any clue?

 

[2informaticos]

You must change U9850.
Liquid spilled from pin 43 to pin1 of J8500 killed GMUX.
You are lucky enough; this board has GMUX, that signal doesn't go directly to CPU...

 

[Don Anton]

Hi thank you for your reply. I replced U9850. still no display. u9850 pin 2 and 44 gets 3.3v. LCD_MUX_SEL 3.3v shooting from the SMC. any clue?

 

[Don Anton]

Just let you knwo. I have replaced the U9850 from same 820-00281 donner board.

 

[2informaticos]

DP_INT_HPD is required to detect the LCD.
You should change U9800 too.
Which pins of J8500 have been affected?

 

[Don Anton]

HI, board siede pins are all clear and no liquid onlt LCD
conncetor . but LCD works fine after cleaning as i tested with working board. pins around 45,41,29,37 & 46, 42, 40, 38. I will change u980o update you now. really appreciate your help.

 

[Don Anton]

wait. thats SMC. you recon I should replace the SMC? Coz this works fine with external monitor .

 

[Don Anton]

dp_int_hpd is 3.3v

 

[2informaticos]

U5000 is SMC.
U9800 is DPMUX...

 

[Don Anton]

Geguis, Display is back. Thank you so much for helping me. one more issue now fan goes high from the start. but everythings works fine no slow any thing.

 

[2informaticos]

Did you connect all the perypherals?
Run HWMonitor and see if appears anything strange.
Try other trackpad and cable.

 

[Don Anton]

yes connected everything properly. any evrything work properly including track pad. but fan goes high. when it starts left fan start first high then the righ one after few seconds. I will run HW Monitor and update you. thank you verymuch.

 

[2informaticos]

"macbook works fine with external monitor"
Did you notice fan issue at that time?

 

[Don Anton]

no fan issue at that time. it worked smoothly with external monitor. fan start high after replacing DPmux

 

[2informaticos]

Recheck all you touched in the process...

 

[Don Anton]

all the sensor resdings on hw monitor is around 20c to 40c no anything high aran rpms are around 5500. I took the board out to check and put is back now no display again?

 

[2informaticos]

Resolder U9800...

 

[Don Anton]

Hi, so sorry for not getting back for a month. I was out of the counrty for a month. I just wanted to tell you that I replaced the u9800 again and its working fine. Thank you so much for help.