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I recently received a Macbook Pro A1502 Retina liquid spill with logic board number 820-3476-a. Unit boots up but no back light. Does anyone know the location of the back light fuse and wled driver? Crazy thing I had it working fine however when installing the OS back light just went out. Also how many volts should I be getting on pin one?
Thanks
I think this might be the location of the fuse
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This is all wrong. You're talking about buying replacement chips without even having a schematic or a boardview. How can you know what to replace without even knowing where to measure??? How do you know the LED driver is bad?
Get a schematic and a boardview for 820-3476, then answer the following questions before further guessing.
1) Do you have 2.7v to 3v enable signal on pin 17 of U7700?
2) Do you have 5v on pins 5 and 18 of U7700?
3) Is R7733 0 ohms?
4) Is feedback network between R7731 and R7732 functioning properly? Traces to resistors good? Resistors themselves good?
5) What voltage do you have on backlight output, pin 1 of LCD connector? 0v? 12v? 20v? 27v?
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It's never the fuse on these. They are smart enough to turn off in case of a fault state.
I have a question concerning this board I have the same 820 3476 a and I have an amber light all the time with battery or without and no power on can you tell me where to start with this the board looks very clean I had to replace the EFI chip because the board did not have one when I bought it doesn't need flashing how to do that Thank you for your help
Hi
I have got 0V on pin 17 of U7700!!!
can you please lead me what should I do?
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allenzabbal, you are correct. The reference designator is F7700 and it is a 3A 32V fuse in a 0603 package and the driver is U7700 and it is a LP8548B1SQ_-04 IC.
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I checked the fuse and it is not open. Can the wled driver fail without and the fuse still ok? Do you know how may volts I should get on pin 1 on the lvds connector? thanks again.
also where can I get the backlight package LP8548B1SQ? Would a LP8545SQ package work?
https://store.ti.com/LP8545SQENOPB-High-...
Thank you oldturkey03 for your help
zzz AKA Louis Rossmann know his stuff along with oldturkey03
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3 件のコメント
Post some top and bottom view images of your logic board with your question. iFixitでの質問に画像を追加する方法
oldturkey03 さんによる
yes F7700 is the fuse
joe さんによる
its probably fine though, they rarely blow even under liquid damage. start probing U7700 pins 17,18 and 5 what voltages do you have
joe さんによる