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820-4924-A no backlight

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Davis

Member
No liquid spill. Tested with KG screen.
pin 1 on LVDS / 0v pin 28-9-30 5v
F7700 /12.57V
R7700/12.57
C7700/12.57V
R7701- PIN1 -12.57 PIN2 12.47 80k
R7702 - PIN 1 12.46V - PIN 2 12.37V 63.3K
Q7700 - Enable PIN 2 3.332V
 
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dukefawks

Administrator
Makes no sense. Pin 2 on Q7700 is an output pin no ENABLE. But looking at R7701/02 then Q7700 is not turned on
Did you test with a good screen from 2015/16 nothing else works. If yes then first check SMC_LID then replace Q7700 and check if fuse is good of course.
 
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Davis

Member
dukefawks said:
Makes no sense. Pin 2 on Q7700 is an output pin no ENABLE. But looking at R7701/02 then Q7700 is not turned on
Did you test with a good screen from 2015/16 nothing else works. If yes then first check SMC_LID then replace Q7700 and check if fuse is good of course.
Click to expand...

Damn it! off course its not pin 2 it is pin 17 (the secound in that row :rolleyes:) yes i tested with 2 different screens for the same model/year.
 
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dukefawks

Administrator
Pin 17 on Q7700, that is interesting....U7700 I suppose.
Is there even an image? Check with flashlight on the back of the Apple logo
 
D

Davis

Member
dukefawks said:
Pin 17 on Q7700, that is interesting....U7700 I suppose.
Is there even an image? Check with flashlight on the back of the Apple logo
Click to expand...

yes there is image, and yes u7700 pin 17 THE FUSE is fine also replaced it for any case..guess replacing Q7700 is next step.
 
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dukefawks

Administrator
SMC_LID?? Are you 100% sure you check with a known good 2015 LCD? inspect LCD connector for damage to. Only then you touch Q7700
 
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dukefawks

Administrator
Because 1.99V is not right! Should be at least 3.2V. SMC_LID is the issue here.
So corrosion on HAL sensor or trackpad/connector.
 
D

Davis

Member
dukefawks said:
Because 1.99V is not right! Should be at least 3.2V. SMC_LID is the issue here.
So corrosion on HAL sensor or trackpad/connector.
Click to expand...

ok so SMC_LID is 3.385 and not as I said before, got some wrong measurements before for some reason..no liquid or other damage on TP and cable.
 
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dukefawks

Administrator
I cannot give any advise when you give bad information. The quality of my advice is as good as the information you provide me. I need to at least know that you are able to use a multimeter and probe the correct part as I cannot see what you are actually doing.
 
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Davis

Member
It was all about the attitude if the measurements was wrong one could think it is because the lid was close which it probably was so just ask the right questions instead of rolling eyes on those newbies, I know where it comes from since I advice newbies in other levels, find the patience and ask the right questions thats all Im asking for.

Ok please lets proceed to the case.
I now replaced U7700, R7700, Q7700, F7700, Q7701, D7710, R7733, C7740, R7744 AND LVDS connector and yes tested with other displays but still no backlight!
try to guide me out Im probably missing something basic..
 
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dukefawks

Administrator
R7752/53. Also check diode mode on these lines. There is not much else to this anymore. You did try a known good LCD from the correct model year??
 
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