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Early 2011 Model: A1278 / 2.3 GHz i5 or 2.7 GHz i7 processor

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Need help identifying a component on logic board

i have a client who spilled a smoothie on her MacBook Pro a1278.

When powered up, the chime sounds and the HD spins, but there is no response from the LCD display.

I noticed that there was a corroded chip on the logic board near the display cable, and was wondering if anyone could help me identify it, so i could figure out if it's the lcd or the logic board that needs repair (i don't have an extra lcd to test if it's the lcd).

Here's a photo with a red arrow pointing to the component.

http://postimage.org/image/fm97fqcqj/

thanks for any help!

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I do agree wholeheartedly with rdklinc. Looking at your image, there is a lot of cleaning left to be done:) now I am not a Mac person, but do wonder about the R005 in your image. (of course not if you edited this;) Anyhow, the R005 sure does look like a current sense resistor, so check on the datasheet right here

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thanks! also, just for my personal reference, what is the function of a current sense resistor? could that affect the lcd powering up?

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sense resistor, do just that, they sense current on a circuit and react on that. These are used in charge circuits as well as part of Apple's SMC circuit. Probably not related to the backlight. It should be easy enough to measure the resistor with a multimeter

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The first thing besides inverter, cables and missing components, clean your board and make sure all the corrosion is removed. You can measure the component with a multimeter, use the datasheet from my comment. It does support what Dan and rdklinc have already stated and is really not much of an answer, but it is the only way to post an image on here. I do not like to use image hosts. The images shows the location of the backlight fuse. It is the same board as yours. The fuse is a 2amp - 32v fuse in a 402 package. It can be purchased at digikey.com and the part number is P15123CT-ND. check it for continuity with your multimeter. Hope this helps, good luck.

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while answering another question, I realized that I have not finished this one. "that is reference designator R5400. It is a 0612 MF 1W 0.005 resistor. It is part of the High Side Current Sense / Filter circuit. Comparable resistors are available at places like this. Hope this helps, good luck.

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You should probably clean off the corrosion with a toothbrush and 90% alcohol, and see if that resolves the issue before trying to come to conclusions.

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okay, will try cleaning thoroughly. can you tell me what a sense resistor does? would that in any way be related to the lcd not working?

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I have no idea what a sense resistor does, unfortunately. Personally, I don't like to guess, so I do troubleshooting by process of elimination and replacing parts, i.e. swap the screen assembly, swap the board, etc. Many of these unibodies have a fuse on the underside that controls the backlight, but if you're seeing absolutely no image, you've probably got a bigger problem than that. Have you tried an external display?

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It looks like your logic board will likely need to be replaced as many components are very difficult to locate or are custom to Apple.

As oldturkey stated you still need to finish cleaning off the junk before going forward.

Also note you have a newer version of this system early '11 model Vs ' late '10 they are different logic bds.

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dan, thanks for that clarification. didn't realize.

i did a thorough cleanse and still no response from the lcd. everything else powers up though, even the backlighting on the keyboard. but the lcd is dead almost like it's not even plugged in.

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You could try plugging in an external display to verify things. I suspect the video circuitry on the logic board is what is damaged. If the external works then its just the internal display side (not the display it's self). In any case you'll need to swap out the logic board.

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thanks. first time i'm experiencing a completely functional logic board with just that component failing like that. i've seen lcds with lines and such, but this seemed unsure. usually i'm used to other parts shorting out. thanks.

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WHAT ARE THE TWO FUSE BLOCKS NEXT TO R005. the TWO THAT ARE TOGETHER ON THE LOGIC BOARD PICTED ABOVE?

REGASRDS

G

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@soundmanjohns, those care capacitors not fuses

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