820-3437 No spill. No power

[bjf]

Not turning on. Not a spill. Board is clean.
- No P3V3SUS_EN
- No shorts
- Has MagSafe light
- 3V42 is good
- PPVRTC_G3H is at 3.3V
- PPBUS is at 8.6V
- No pulsing on any voltage lines
- SYS_PWROK_R is at 0V. No pulsing
- CPU not shorted
- PP5V_S4RS3 is at 0V and no pulsing
- PM_DSW_PWRGD is at 3.4V

Not sure what to assume besides dead CPU. Any other thoughts?

 

[2informaticos]

PCH's RTC signals (4 in total)?
PM_SLP_SUS_L, PM_BATLOW_L, SMC_ADAPTER_EN, PCH_DSWVRMEN, 32KHz from U1900?

 

[bjf]

PM_SLP_SUS_L: 0V
PM_BATLOW_L: 3.3V
SMC_ADAPTER_EN: 3.3V
PCH_DSWVRMEN: 3.2V

I don't have an oscilloscope but U1900 only has .011V on pin 12 PCH_CLK_RTCX1. This is low. I would expect to see something closer to .4V

 

[2informaticos]

Check power 2, 13 for U1900 and pin 1 too.

"PCH's RTC signals (4 in total)?"
Where are???

 

[bjf]

Got it. This is the one customer in a thousand who isn't lying when they say it was only a drop. There was the smallest amount of corrosion imaginable on pin 12 of U1900. I had to pull it and reattach it to remove the short. All good now. Thanks for getting me there.