A1369 820-3023 backlight problem

farfan14

Member
hello. have 820-3023 with backlight problem.when flat cable of I/O board is discconected have backlight several seconds. whats should be problem? thanks
 

farfan14

Member
1) so. without LIO board connected SMC_LID have 3v and backlight present after about 5-6 seconds backlight dont have but 3v still present.
2) withi LIO board connected always havr 1.1~1.3v and no backlight at all
 

2informaticos

Administrator
Staff member
There is a problem with lid sensor, placed on LIO board.
Apart of that, some problem must be on the MLB too, if backlight disappears.

First, do PRAM reset 2-3 times.
If no change, check BKL_EN/PWM.
 

farfan14

Member
so i tried like this

1) without LIO board connected BKL_EN have 2.6v and BKL_PWM have 3,3v. after several second backlight goes off and both voltages dropping to 0v
2) with LIO board connected BKL_EN have 2.6v and BKL_PWM have 0v.
 

2informaticos

Administrator
Staff member
No need to connect LIO board.
In fact it has a problem and you will need to fix that too.

Did you test known good compatible LCD assembly?
You may need to change U9701.
Inspect its area for corrosion.
 

farfan14

Member
yes i tested this lcd on another macbook and also another lcd on this macbook. now i changed u9701 and nothing changed. exactly same problem remained.there is not any corosion
 

farfan14

Member
yes i checked lio boar disconnected also of course. very important thing what i missed to detect and write here. fisrt boot is normal have chime and fan is rotating normaly after several seconds fan stops rotating and macbook is like turned off but ppbus_g3h have 8.4v. with and without LIO board is same only different is that without LIO board backlight working and we can see apple logo and loading bar after loading bar completes about 70% macbook is turning off. but ppbus_g3h have 8.4v as i said. with LIO board connected also we have apple logo and loading bard and after 70% turning off. but no backlight with LIO board before its turning off.
 

farfan14

Member
its very old model and i hope someone have this problem in experience. i hope you have some ideas about this problem 2informaticos

thanks in advance
 

2informaticos

Administrator
Staff member
Get good LIO board/flex and test again.
Let see if beeps RAM error.

You can also run the corresponding ASD.
 
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