820-4924-A problems with PP5VS3_EN

[KC Micro Tronix]

I am working on a 820-4924-A "I get to go to war with this one" no time restrictions!

the PP5VS3_EN line is missing. So obviously PP5V_S3 is not turning on.

The PP5VS3_EN line is reading about 0.7V. I have seen this line shorted before so I checked resistance to ground it it was good. About 100k Ohms.
I isolated U7501 pin 4 (EN) by moving R8179 off the pad and PP5V_S3 came on and there is 3.4V on pin 4. I now have 0 volts on the "CPU" side of R8179 which is PM_SLP_S4_L.

Thermal imaging shows heat in the processor area. Unit is pulling 130 mA. No other thermal hot spots that are out of the normal.
I know that PM_SLP_S4_L comes out of the CPU directly. I get this sinking feeling that I am dealing with a bad CPU but am not confident.

I am a little confused. the "L" means it should be low to enable? I really do not have a solid grasp on this circuit or the order of the S3 enable state. I would think the system would be trying to enter S3 just by giving it power. Then move on to S0 if the SMC is happy with what it sees.

Please give me hope

 

[2informaticos]

Removing R8179 will force U7501 to generate 5V_S3, but the board will not start; as PM_SLP_Sx_L signals are not correct.
What about PM_SLP_SUS_L, 3V3_S5 and 3V3_SUS?
Cannot catch any pulse at PM_SLP_S4_L when trigger SMC_ONOFF_L signal?
Post SMC_ADAPTER_EN, PM_BATLOW_L, PM_RSMRST_L.
Be sure to use 60/85W Magsafe 2 charger; not adapter 1-->2.
Did you try to start in SMC bypass?
Also post exact voltage for PPBUS_G3H.

 

[KC Micro Tronix]

1. I soldered back R8179

2. CPU is generating slight amount of heat




requested measurements

using 60W MagSafe cable on bench top power supply

1. 3V3_S5 - (3.3V)
2. PM_SLP_SUS_L - (0V)
3. 3V3_SUS - 0v (P3V3SUS_EN 0V)
4. PPBUS_G3H - (12.5V)

I did not detect pulse at PM_SLP_S4_L when trigger SMC_ONOFF_L signal?
I power cycled the unit during this test.

1. No voltage momentary or standing of any kind at PM_SLP_S4_L

Did you try to start in SMC bypass?

1. How is this done with a board on the bench and not in the machine?

* Side note. I am able to see active data lines in and out of the SMC so it is communicating with the machine and appears to be alive. However the enable states are still not turned on and I don't know why. Is this a wake CPU thing or is this a SMC line thing?

 

[2informaticos]

"How is this done with a board on the bench and not in the machine?"
What about using R5115/16 pads, instead of power button?

"PM_SLP_SUS_L - (0V)"
Check all RTC signals for PCH, page 12.