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.

 

[2informaticos]

Read about diode mode checking here:

HOW TO collection

I hope this "How to" collection will help our members. I will possibly modify this post in time, if updates available. Trigger SMC_ONOFF_L (PMU_ONOFF_L): It reffers to simulate power button function, when the keyboard is not connected. We need to do this when we work with the board...

boards.rossmanngroup.com

What relation did you see between pin 3/J7000 and L7560???
Do you get PPBUS_G3H and 3V42_G3H?

Do you habitually inject voltage without real reason?
Tell us which, if had any this time...

 

[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

 

[2informaticos]

So you don't get PPBUS_G3H, nor 3V42_G3H.
Why then expect voltage at L7520 (5V_S4RS3)???

Post diode mode to ground at F7140 and L7095.
If no short, post U7090 voltages; use surrounding components as test pads.

BTW (for the future), you can perfectly write 0V instead of 1.3mV; which is a non-sense reading.
0.24V looks also much better than 240.2mV.
Do not think that 4/6 digits multimeter helps more than 3 digits one...