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A2141 - 820-1700 - Liquid damage on screen board.

R

ronaldo

Member
Hi, everyone
Please I need help with these Mac.
Liquid damage on-screen board and logic board had some oxidation around C1171.
After cleaning the corrosion and oxidation the board turns on, but no display. Tested with another display and still same.
If I leave the battery connected it turns on and all voltages are present but keep looping every 20 secs.
Without a battery the voltages 20V, 0.0465Amps, 0.950W.
L7600 - PP5V_G3S - 5.13V
L7660 - PP3V3_G3H_T - 3.35V
F7001 - PPVBAT_G3H_CHGR_REG - 12.6V
No other coil has voltage.

But, if the battery is connected the voltages seams normally everywhere for 20 secs, then keep looping.
The voltage on the Amp meter with battery is like 20V always, amps go to 2.2 and drop to o.4

Link for the video showing the power cycling on Amp Meter
 
T

tcampbell34

Member
The battery is probably bad. The batteries on the 16" die all the time and then it will only give you a low battery symbol on the screen and then turn off. Also U9850 is probably bad if you had liquid damage near the LCD connector. You can check diode mode values on the EDP_INT lines on the LCD connector to confirm. Replace U9850 and LCD connector on the screen and try a know good battery.
 
2informaticos

2informaticos

Administrator
Staff member
Before searching for video issue, should confirm USB activity.
At least check for voltage at L7211; should drop to aprox 0.6V after 10-15s.
 
R

ronaldo

Member
on L7211 starts at 1.9v then drop to 0.69v and after 25 secs 0v.
USB ports are normal
Is it normal for the CPU to boil hot just after plugging the charger?
 
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R

ronaldo

Member
tcampbell34 said:
The battery is probably bad. The batteries on the 16" die all the time and then it will only give you a low battery symbol on the screen and then turn off. Also U9850 is probably bad if you had liquid damage near the LCD connector. You can check diode mode values on the EDP_INT lines on the LCD connector to confirm. Replace U9850 and LCD connector on the screen and try a know good battery.
Click to expand...
The battery is good as I've tested the same battery on another mac I had from another customer and it worked fine.
I will check the U9850.
The liquid wasn't near the screen connector on the logic board, but on the little board on the screen.
 
2informaticos

2informaticos

Administrator
Staff member
Droping CPU core looks like board boots.
However, should be good to confirm USB activity.
I'm not sure what you've menat with "USB ports are normal".
Also test for external video.

You've been asked to check diode mode to ground on EDP_INT lines.
T-CONN board is connected to J8500, with the small video cable.
Any liquid problem is transfered directly to MLB!
 
R

ronaldo

Member
Diode mode LCD disconnected.
EDP_INT_AUX_N - 460
EDP_INT_AUX_P - 461
EDP_INT_ML_N<0> - 409
EDP_INT_ML_P<0> - 406
EDP_INT_ML_N<1> - 408
EDP_INT_ML_P<1> - 408
EDP_INT_ML_N<2> - 412
EDP_INT_ML_P<2> - 408
EDP_INT_ML_N<3> - 408
EDP_INT_ML_P<3> - 407
----------------------------------------------
I've connected a mouse with a USB-C adapter and it stays on for the same period as the mac stays on about 30 secs.
On the external video, it recognizes the signal and the monitor shows that black screen just before the apple logo. But looks like just when it tries to show the apple logo the mac restarts.
With another LCD the backlight goes on and then the same behavior I mentioned above happens.

Something I just realized is after connecting the trackpad it stays on for only 5 secs and restarts. So I've removed the trackpad and it has liquid on it.
So, the trackpad is faulty, but even with it disconnected it remains the same as mentioned on above (30 secs on and restarts).
 
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2informaticos

2informaticos

Administrator
Staff member
It restarts with both charger and battery connected?
Is the battery charging?

Something else was affected by liquid on the MLB, or other device connected to it.
Test the board alone on the desk and see if CPU core voltage stays on; or check USB activity properly.

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...
boards.rossmanngroup.com boards.rossmanngroup.com

You can try DFU revive, just in case.
BTW, be sure to use proper charger; 96/140W for this model.
 
R

ronaldo

Member
It is restarting with and without a battery.
The battery is charging fine and it same thing happens only on the battery.
Only the LB alone same thing. CPU core goes to 1.3V then drop to 0.69V and after a few secs restarts.
USB activity on a USB stick with LED light. The USB stick power on starts to blink and goes off.

Here you can see the power loop under the thermal camera.
I notice that the GPU and CPU get hot right after pressing the power button. I don't know if it's normal.
You can notice that the PCH - U1200 shines for a sec under the thermal camera.

Thanks again for your patience and help.
 
R

ronaldo

Member
Yes, that's the one I'm using. 96W.
On DFU mode it reacts the same. It goes to DFU mode and the same happens after about 30 secs.
 
R

ronaldo

Member
Quick update.
After replacing U9850 I manage to put it on DFU mode and all voltages stayed on.
Done the revive and the Mac is alive.
Thanks to everyone that help me out here.
 
2informaticos

2informaticos

Administrator
Staff member
Thanks for solution feedback.
These weird MacBook T2 issues can only be repaired sometime with repair notes from other people.
 
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