Chosen Solution
So I bought a 13” Macbook Air with an 820-3437 logic board that the owner said the backlight went out so he took it to a shop to have the backlight fuse replaced. Well I guess the shop replaced the fuse, doing a poor soldering job at that but also rendered the computer unresponsive. i get a solid PPV342 but PPBUS is oscillating between 8.6 and 7 volts. I hear a ticking sound around the SMC area. could that be shot even though I am getting PPV342? I am at a loss on this one.
Not very uncommon that people selling faulty machines just tell part of the whole story. I doubt anyone with experience in component level repairs would replace a random fuse when the machine doesn’t even start up. It seems you have a faulty main power line there, PPBUS_G3H should have a steady voltage. Ticking probably comes from a faulty mosfet and it’s impossible to tell which mosfet it comes from just by the ticking noise. It may as well be a faulty U7000. No way to tell without isolating the problem, but replacing at once U7000 and the 5 close related FETs would give good chances to solve the issue.
