Try taking the topcase off completely, and bridging the power-on pads on the board with tweezers. If it behaves exactly the same, then at least you've ruled out topcase issues. Or I guess an even simpler way to deal with this is: Does the optical drive make noise as a response to pressing the power button, or does it make noise automatically when you connect to the AC? If it responds to the power button, your topcase is likely good.
I would also test your RAM slots by attempting to power up with one populated and the other empty, and then with the other populated and the other empty.
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It's a boring suggestion, but the common denominator with both boards is that you're got the same left I/O board in there, so it may be worth swapping that out to see if anything happens.
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It's a boring suggestion, but the common denominator with both boards is that you're got the same left I/O in there, so it may be worth swapping that out to see if anything changes. It's much cheaper than the board itself, so I always try swapping that before taking a massive gamble and buying a new board.
Also, remove the battery, and disconnect the optical and hard drive cables. Until your computer has a pulse extraneous components will only complicate the issue.
Try taking the topcase off completely, and bridging the power-on pads on the board with tweezers. If it behaves exactly the same, then at least you've ruled out topcase issues. Or I guess an even simpler way to deal with this is: Does the optical drive make noise as a response to pressing the power button, or does it make noise automatically when you connect to the AC? If it responds to the power button, your topcase is likely good.
I would also test your RAM slots by attempting to power up with one populated and the other empty, and then with the other populated and the other empty.
It's a boring suggestion, but the common denominator with both boards is that you're got the same left I/O board in there, so it may be worth swapping that out to see if anything happens.
Also, remove the battery, and disconnect the optical and hard drive cables. Until your computer has a pulse extraneous components will only complicate the issue.