820-4924 No CPU Vcore

bighead

New member
Hi,

I received this board. It was liquid damaged
I don't know where exactly, because it was cleaned before I received it.

Corrosion:
Around LVDS
KB backlight connector
J6100 - I removed it
U7200 - some corrosion next to it.

I cleaned the board.

The board goes to S0 state, but CPU Vcore does not present.
Missing CPU_VR_EN.

PPVMEMIO_S0_CPU 1.205V
PP1V05_S0 is present.

ALL_SYS_PWRGD - 3.3V

Y1905 - oscillates
L7630 - 1.05V
PCH slowly gets warm

U7200 powers on as far there are PP5V_S0 and PPVIN_S0_CPUVR_VIN.

Should I just change U7200 or is there something I'm missing?

Thank you.
 

dukefawks

Administrator
Hmm, that does mean that CPU_VR_ON must be there or there must have been a pulse there. R7201/2 and traces are suspect
 

bighead

New member
I rechecked R7201/2 and everything looks fine there. I've the right voltages on them.
I checked CPU_VR_EN if there is any pulse on that line, but nothing at all.
Checked the resistance on VR_ON again and it's open, so there is no short.

I'm trying to figure out what needs to get that signal.
Looks like it comes from the CPU.
ALL_SYS_PWRGD high and PM_PCH_SYS_PWROK is also present. Is that possible that trace damaged?

I checked R1955 also. No pulses on it.
 
Last edited:

dukefawks

Administrator
It could be anything. The CPU needs to be alive to enable the VR_ON. Could be dead CPU or corrosion under SMC/CPU.
It could be U7200 but it would be my last suspect.
 
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