820-00239 Not turning on.

[bjf]

This board had some light corrosion on both UB400 and U3200. Other than that I can't find any corrosion other than a little bit near the power button. All of it clean up well in the ultra-sonic cleaner. The board has 20V coming in and has 13.05V on PPBUS. PP3V3_G3H is at 3.4V. PP3V3_S5 is at 3.3V. 3V3_SUS is at an unstable 0.050V. 5V_S5 is at 5V. No cycling on 5V_S4 or PPVCC_S0_CPU. Can't find any shorts. Not sure where to go next.

 

[2informaticos]

PM_SLP_SUS_L pulsing, or steady 3V?

Disconnect power button and battery.
MLB should start automatically when charger is connected.
If not, try to start in SMC bypass mode.

 

[bjf]

PM_SLP_SUS_L is pulsing.

 

[2informaticos]

No pulse at all on other PM_SLP_Sx_L signals?
Check for short at 1V0_SUSSW and 1V0_SUSFUSE.
Does these voltages pulse at least?
Also check for short on big coils.

 

[bjf]

PM_SLP_SUS_L is the only one that's showing any sign of life. It's not pulsing in the normal up and down way, it's just bouncing around at very low voltage levels. All the other PM_SLP_Sx_L signals lines are at 0V.

No shorts on anything that I can find. IR camera isn't picking up any heat. No shorts and no voltage on 1V0_SUSSW and 1V0_SUSFUSE.

 

[2informaticos]

Check RTC signals and 32KHz oscillation.

 

[bjf]

RTC_RESET_L is at 2.7V. R5112 has 1.7V. Outside of that I'm not sure where else to look for 32KHz oscillation.

 

[2informaticos]

Check PCH_SRTCRST_L too.
What is the exact voltage for PP3V0_G3H?
RTC_RESET_L looks a bit lower than normal.

 

[bjf]

PCH_SRTCRST_L and PP3V0_G3H are at 2.7V. PP3V3_G3H is at 3.4V.

 

[2informaticos]

2.7V at PP3v0_G3H is not correct.
This can be a sign of bad U7800, or PCH/CPU...