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Mid 2009 Model A1278 / 2.26 or 2.53 GHz Core 2 Duo processor EMC 2326

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820-3115-b no backlight issue but has video

I have a MacBook Pro 820-3115-B.

There is no water damage and the customer brought it in for a thermal paste cleaning.

I changed the paste and put it all back together to find out they no longer have backlight…

The LDVS Cable has no damage nor the connector as I checked all the pins for damage….

I shined a light from the back and you see a image just no backlight…

Anyways, I am very little experienced in board level repairs and reading schematics but I did check the fuse… I thought it was that an I removed and ran a micro wire for testing and still no backlight..

However though the fuse reads when turned on and booting 11.7volts which I thought should be 12.5 volts

I also tested:

Capacitor C9710 1 Pin, the voltage is 5V

R9731 and R9715 to split voltage, the voltage measured is 2.9volts

Measure the resistor R9704 2 Pin, it has 3volts

I am not sure if U7901 IC Is blown for some odd reason. I take these MacBooks apart all the time and never had this issue….

Can someone guide me fixing this and what else to check….. I don’t know what else to do

Answer this question I have this problem too

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@gns_solutions what voltage do you have on L9701 /D9701

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With no screen plugged in I tested them in dc mode and get 0 volts

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Any other things I can try? I literally just took the board out and changed the paste and put it all back together and the backlight stopped working. It doesn’t make any sense

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It may if you accidentally shortened something out on the connector. Have you checked if you get a backlight enable signal? Do you get the 5 volt to your driver from PP5V_S0_BKL? You obviously have the schematic so check the individual traces/components

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But how can I short the connector when the battery was unplugged . I plugged cable back in and it was fitting right then I plugged battery back in

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2 Answers

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I have changed you to the correct icon according to your logic board.

820-3115-B

820-3115 2012 2.5 i5 Apple Motherboard 661-6588 MacBook Pro 13"

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This is a mid 2012 MacBook Pro according to the serial number 13”

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@gns_solutions see if the serial number (printed on the RAM slot retainer and the serial number on the back of the machine are the same. Also, you did not give us that number so all I had was the board number.

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i did solder the top resistor back to where it belonged as I noticed it touching the bottom one

that most likely caused the short and killed the u9701 chip. I’m assuming overtime the resistor got loose and touched the other one and that did it…

so now u9701 cannot boost to 25 volts..

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