How to troubleshoot no-power condition?

Hi all,

New poster here :) I have a MBA 11" Mid-2011 machine that I purchased to restore. When the power adapter was plugged in (known-working), the green light was only faintly illuminated. It turns out that the machine came to me without a cable for the I/O board (Thanks iFixit!). Upon installing a proper I/O board cable, the light illuminates at full brightness.

The issue is that the MBA does not respond to power button presses at all. It did charge the battery (orange LED on magsafe). I tried an SMC reset as detailed on the Apple Support page, and the Magsafe LED responded (by temporarily changing to green and then returning to orange). No change in the MacBook's condition.

I did notice a small amount of liquid damage to the top case (keyboard and trackpad board), so I replaced that with a known-good one. Still no dice. There does not appear to be any visible liquid damage or corrosion to either side of the logic board, although I know that is not a 100% indicator.

My question: Are there any specific component-level items to check? Are there any fuses in the MBA logic board that could be preventing power-on (like the PowerBook 2400 of long ago)? Voltages to check? I know that "replacing the logic board" should fix the issue, but I just wanted to check and see if anyone had any other suggestions.

Thanks,

Kyle-