Power logic board from DC supply

I have this old Macbook Air 13" (A1466 820-3209) which possibly has some liquid damage (not really visible), DC-in board has some damage. So before I get a new one, or attempt to repair it, I would like to test the logic board with a DC supply to see if I get fan-spin.

But where to connect my psu ? Should it be at the dual diode between the battery and adapter D6905 , or is R7020 better ?

Thanks !