820-00281 ON CRITICAL UPDATE U4200 VERY HOT

huzeafa

Member
Good day guys, am currently having a 15 inch board with critical update error and crashes , I followed up to U4200, ( by the way, I have had an issue like this I past, which I was able to solve, thanks to @2informaticos , just turns out to be a different cause this time ) the U4200 (Berkelium) gets very hot, so I want to replace it , but am not sure if I can take from the same donor board and get the machine to work, please help guys
Also on PP3V3_S4_SOC_PMU I get 0.077 on diode mode , which is slightly lower than a functional board , but surprisingly, I get 3.3V still on that line, though U4200 gets really hot
 
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2informaticos

Administrator
Staff member
Do you get all voltages controlled by U4200?

Did you try external monitor, disconnecting internal LCD?
This way can discard an ALS/CAM issue.
 

huzeafa

Member
Yes I do get the voltages controlled by U4200, please help me answer the part of the the chip getting hot and the replacement option. Also about about how diode mode measurement is lower than a reference board .
Thanks for your time
 

2informaticos

Administrator
Staff member
"Did you try external monitor, disconnecting internal LCD?"
???

U4200 can get hot because of excessive current consum of other chip.
Lower reading in diode mode can be caused by U4200, or something else connected there.
 

huzeafa

Member
I tried an external display with internal screen disconnected , but the result is the same, and U4200 still gets extremely hot, can I replace it ?
 

2informaticos

Administrator
Staff member
If you still get critical update error on external monitor (internal disconnected), then is not ALS/CAM issue.
There are few things more to check, mentioned by dukefawks; you should have that information saved on your PC.

Not sure if U4200 firmware is board dependant, but shouldn't be a problem if you pick it from same donor board.
 
Just received a Mac from eBay very similar to this one.. Couldn't get around critical update. No touch bar or keyboard backlight.
Clean everywhere but when looking under u4200 I noticed junk around pins 36-84 so I replaced from a donor board.
Mac took a while to boot the first time but everything worked and no more critical update error.
Not sure if this was the same mac.. but this definitely solved the problem for me.
 
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