820-4924 Missing PPBUS_X239_REG

[Ryanlen2]

Minor liquid damage around clock area, but board was still working. I replaced the really nasty looking stuff just to be safe. Now board doesn't work at all. Going down the power rail list I found that PPBUS_X239_REG is at .015V and is supposed to be a 12V rail.

Q7979 Measurements

pins 1,2,3 @ 12.51V
pin 4 @ 11.70V
pin 5 @ 0.015V
Resistance on PPBUS_X239_REG, 97.4K

Thank! a good one.

 

[2informaticos]

"PPBUS_X239_REG is at .015V"
Did you measure with trackpad connected?
However, that voltage is not required for the board to turn on.

Which components did you change?
Check all of them and their traces.
Do you get 3V3_S5, 5V_S5, 3V3_SUS, PM_RSMRST_L, 5V_S3 or/and other voltage?

 

[Ryanlen2]

Thanks for the info on PPBUS_X239_REG not needed for turn on.
I just went back to the area and noticed that I have PPVRTC @ 3.3V on pin1 of c1910 but PPVRTC goes down to 2.7V by the time it gets to C8090/1/2. This is most likely my problem?

I replaced U1900, Y1905 and surrounding components.

 

[Ryanlen2]

I think I found it. I have poor continuity between pad 1 of c1910 and the rest of PPVRTC components. Will run a wire and see what happens. Thanks.

 

[2informaticos]

OK, waiting your feedback...

 

[Ryanlen2]

That was it. Im all set. Thanks for the help. Much appreciated!

 

[Ryanlen2]

Unfortunately i think I spoke too soon...

I have 1.8V on PPVCC_SO_CPU but no post /no chime/no video. No light on USB Mouse either.

I dont have an O scope so all I can give are Voltages on U1900, sry.
Also all signals seem to be properly reaching their destination.

https://photos.app.goo.gl/sQpgxDPehjNw5Egq8


u1900
pin 1 - 3.324V
pin 2 - 3.324V
pin 3 - .965V
pin 4 - 1.18V - 1.2V
pin 5 - 3.325V
pin 12 - .324V
pin 13 - 3.405V

Y1905
pin 1 - .960V
pin 3 - 1.208V

Thank you. have a good one!