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2.2 GHz (Turbo Boost up to 3.4 GHz) or 2.5 GHz (Turbo Boost up to 3.7 GHz) quad-core Intel Core i7 processor with 6MB shared L3 cache.

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MacBook backlight not working, need help with diagnosis

Spilled coffee on the upper keyboard/fan outlet. Wiped off and left powered on (I now know that was stupid)— after a couple minutes one string of LEDs turned off, followed by the other. The display still works (can test with torch behind apple logo) and it can still drive an external monitor. Board number is 820-3787-A.

I have had a good look at the logic board and nothing obvious—main fuse is okay, LCD connector seems okay, WLED driver is okay and supplying correct voltage.

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I have a .brd of the board and have checked some other components. This chip Q7706 appears to be the culprit. From the schematic it looks like pins 6, 5, 2, 1 should have 12.6V when pins 3 and 4 supply 12.6V. I am getting 0v on 6, 5, 2, 1. Would it be reasonable to assume that the chip is dead or is it more likely a short somewhere else?

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Also I notice that the capacitor C7701 on my board is missing, shown in upper left of the yellow circle. Could this be a difference in board schematic or could it have burnt off?

Would appreciate some help before I continue any further. Thanks!

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C7701 is not on the board as it is marked as No stuff.

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@imicrosoldering Ah that makes sense, thanks.

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Looks like you’re on the right track! Do you have access to the needed parts as well as have micro-soldering skills?

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Thanks, that's good to hear! Yeah I've found the parts online, and I have some experience with PCB soldering at this level—but not with anything so expensive, so I'll have to practise with some other broken board lying around.

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Hi Dan, still having trouble with this— I've replaced the Q7706 but I don't think I needed to, after more reading (and a better understanding of MOSFETs), it was actually deactivated because the led driver sensed a short. I'm thinking it's the lcd connector or cable, there is only 10ohm between pin1 and ground. Is there any advice you could offer?

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Then you have corrosion damage within the LVDS connector and/or the solder joints. Go back and inspect it.

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Seems okay, no obvious corrosion— with the lcd cable out I'm still getting 10ohms between pin1 and ground (on the cable side) though, would that be an issue?

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Sam Brown will be eternally grateful.
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