Liquid damage, post logic-board replacement, still doesn't boot

The MBP in question had a soda spill last September. Finally got the correct logic board and replaced it this afternoon. Plugged it in, let it charge for about 30 minutes and tried to boot. Optical drive did its thing (mechanical noises), it made the happy MBP booting up noise (known in my home as the WALL-E sound), and stopped there. The keyboard backlight works, and the LED at the front right corner is turning on and off slowly. I can see the screen is getting power; it's still black, but it's a "powered" black.

My question is, is there something else I should be doing? I have seen several references to a PRAM reset and a PMU reset, both of which were alluded to in situations similar to mine. How do I do these things and would they help?

I heard the sound and got excited. Now I'm down in the dumps again.

Answered! View the answer I have this problem too

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I would delete this, but I just wanted to give some further information for someone who may be in a similar situation. It turns out that it is booting up and going through the complete process. The machine works fine; it's the screen backlight that's not working for some reason. I worked on this thing in a sunny room around noon. When the sun moved, the room got darker and I could see the image now. Hah! Getting closer.

Now, what would cause the backlight to not work? I'm going to dig back into the guts and make sure all the connections are well seated. Hopefully it's something simple like that. Any other possibilities?

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I've been searching all around for a solution to this. One individual had mentioned that he had a near identical issue and fixed it by replacing the I/O board. I'm not familiar with the location of this. Anyone know if this could help or is it a bunch of hokum?

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Also, how difficult is it to change out the LVDS cable? I'm under the impression it requires a breakdown of the display assembly, yes?

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Yes it does. Most people replace the entire display assembly, then sell the good LCD to offset the cost.

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My concern is that it's not the LVDS or the screen, but something else. Are there any multimeter tests I can do to help pinpoint the issues? I have a schematic of the board, but it doesn't say anything about what voltages should be at what points. I'd like to get into this a little less blind, if you know what I mean.

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Check your LVDS cable connector. On your MBP model the LVDS cable carries video and power to the LCD backlight. Since you have a new logic board but probably using your old cable it could have been damaged (shorted) by the liquid spill. If you see black spots on the pins, clean them and try the cable. If you still dont have screen lightning then you could have to replace the LVDS cable. Another troubleshooting step would be to power up your machine directly from the logic board after disconnecting the top case from the logic board to check if you still have the lightning issue. If not then the problem is top case related. Liquid spill on a computer can lead to unexpected issues and sometimes many parts can be affected. If the liquid was not directly spilled on the top case then forget the top case inspection.

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So, it's a possibility that it's just the LVDS cable? I hope so. I can get one of those easily...

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David, either, the LVDS cable is not seated properly, the cable connector is bad, the cable is compromised or the new to you logic board has problems with the backlight circuitry. I'd inspect the connector on your LVDS cable for burn marks etc... clean it if necessary (as suggested by lemerise), then try reseating it and give it a whirl. If the connections are contaminated or not seated properly they fail.

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I'm just hoping it's not the display.

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The backlight system is fused, on the logic board. The fuse should have died prior to any high current getting to the LED backlight and damaging the LEDs. I would not worry about the screen unless you dumped soda up there too.

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This could have happened if you originally blew out your lvds cable coming from your lcd display from the original spill so please check the lvds cable to make sure none of the pins on the connector are burnt/black/bent/damaged if so then most likely you blew out the new working logic board with a bad lvds cable from the your old machine, seen it happen way to many times before but if your lucky you may just have to replace a 2amp fuse to get the backlight working again

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The connector was clean, shiny and showed no signs of damage.

Where is this 2A fuse you speak of? If I could just get in there with my Fluke I might be able to figure out which component is having issues.

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