Did you check the power rails? Why do you think the one wire circuit is bad?
While a warm chip maybe bad, it’s not the first thing I jump to. More often I see liquid damage as the root cause when I get a dead system.
As the MagSafe LED is not lighting leads me to checking the MagSafe connector first for dirt and bad connection contact. Did you try tracing the middle contact to the SMC logic.
I make a through inspection of the logic board on both sides looking for corrosion and/or burnt components.