820-2879 LCD connector shorted now won't power up

Hi, I have an 820-2879 where the LCD connector locking arm shorted out the connector.

I have a green light on charger but no power up. I am trying to learn board repairs so thought a good one to start on.

PP3v42_G3H is at 3.48v but

I'm finding PPBus_G3h on the output of F7040 to be going from 12.8 - 2.8 pause then starts again at 12-8volts and goes down.

I am trying to learn so presume U7000 is what helps produces PPBus_g3h is that correct?

Q7030 has the same irregular voltage on pin 4.

Am I looking down the right line, can I have some help/advice please on where to go next?

Could it also maybe be something trying to turn on then can't hence why it goes back through the voltage cycle.