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[SOLVED] 820-4924-A backlight issue

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premtec

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The MacBook had spilled liquid and the issue is that after some cleaning and replacing C5125 now chimes and display image but no backlight until I close and open again the display.
After that it has backlight but if I close again the display the backlight doesn't go off.
I couldn't find any schematic so I used from 820-3536 because they are too similar.

PPVOUT_S0_LCDBKLT is 49V when I have no backlight and 38V after using a magnet at lid switch and the backlight works.
R5171 has 3,2V at pin 1 and goes down to 0V with a magnet at lid switch.

SMC doesn't look to have any corrotion and the liquid trace at the top case seems that didn't touch it.
LID switch also is perfect.



are there any ASD diags for this model?
 
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dukefawks

Administrator
49V means no load on the backlight. Either damaged connector or cable. Could also be the connector inside the LCD if the one on the board is fine.
 
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premtec

New member
Yes but as I mentioned if I pass a magnet from the lid switch I have backlight after that and the voltage drops to 38V.
If I had and issue with the connector or the cable [both look fine] shouldn't I have permanent problem?
 
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premtec

New member
The issue is that I don't have a same MacBook to make that test, but as I mentioned the issue happened after liquid spill and the path of liquid was from edje of battery through charging cirquit and near smc [without touching it] at the top side of the board only and LCD connector is at the bottom.
The LCD even though it gets the high voltage for the backlight seems to need also an enable signal in order to use it - I can't figure out what but by the time you trigger for a moment the lid switch it works after.
 
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dukefawks

Administrator
I have no idea. It makes no sense to screw around with the board if this is an LCD issue. Get a cracked assembly for testing or something, must be 2015+ model!

You did check SMC_LID is 3V?
 
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premtec

New member
Today I had same model for service, with the second display works perferct!
Thank you duke for the instuctions.
 
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