820-00164 No power to pin 3 @ J7000

[prodigy83]

I am stumped, I am getting power to pins 1 and 2 @ j7000 14.86v, but I get only .8mv @ pin 3.
I have replaced L7560, U7090, and D7005, because they seemed to get pretty hot with the thermal cam. The LIO board I also replaced.
I did inject voltage to a line which which led to the processor (forgot to write down where), and the processor did heat up, so it looks like that is working.
I am a bit of a novice when it comes to checking resistance to ground, or anything really that is not a short ( I rely a lot on my thermal cam).
History on the board is it did have liquid damage, but I believe I have cleared all this up. I had the board sitting in a drawer for a while, it looks like all the components are there. Where can I go from here? Thank you.

 

[prodigy83]

Thank you, I have saved your article as a PDF for future help. I have watched Jessa's videos from iPad Rehab about placing the red probe on ground and using the black probe to measure. My issue is I just do not understand how to use this without having a "known good" board in my possession, which I often may not have. I tried watching Louis's slideshow presentation he made a few years back, but it is hard for me to follow.
I only try to inject voltage when I know a short is somewhere, or if I think there may be a short

I know pin 3/J7000 has no correlation with L7560 however I would imagine that something like L7560 may be originally responsible because I was getting pulsing at first, until I removed the chip and replaced it. When I replaced it, the voltage on pin 3/J7000 went to nada.

If I do inject voltage, I always start low, but never go over the voltage the chip is supposed to handle. So if it is 3V42, I never go over 3.42v. I usually find any shorts way before I would get to this, if there is a short that is. Am I doing this wrong?

1.3mv @ pin 1/F7700 for PPBUS_G3H.
240.2mv @ pin 1/J9500 for 3V42_G3H
Thanks