Macbook A1990 820-01041, missing PCH_RTC_RESET_L / PP3V0_G3H_RTC. 20V 600mA no charge

[Paul Daniels]

3rd tech looking at this machine.

LD on U9801, U9850 (GPU MUX related) - replaced
LD on U7370 - replaced
LD on U1950 - replaced

So far nothing has resolve the primary issue where the machine will fire up to 20V, spike 800mA for a moment, then reduce to 600mA constant and run the fans from 'standard' speed up to 'full speed' within a few minutes.

Have gone through a rails list and it stops with PCH_RTC_RESET_L missing (0V) and likewise PP3V0_G3H_RTC missing.

Diode mode for PP3V0_G3H_RTC is ~0.6. No LD around PMIC/Calpe

No battery charge occurs but the board will run off battery.

Power on/off is achievable. Machine is not DFU/RECOVERY mode either (plugging in to an AC2 machine yields "Unable to power/use this thunderbolt device".

 

[2informaticos]

What about other U7800's LDOs (page 76)?

 

[Paul Daniels]

All other LDOs present, LDO_RTC @ 1V5.

LDO_0/1/2_IN also present, likewise VIN_RTC_*

 

[Paul Daniels]

UPDATE: U5870 had corrosion on it, replaced, got my 3V0 RTC PLATFORM_L etc all back and get all the way to ALL_SYS_PWR_GOOD, PM_PCH_PWROK and PM_PCHSYS_PWROK and everything "online" but it still doesn't boot. Still ramping the fans too.

1am, time to put it aside and try again tomorrow.

 

[2informaticos]

What is CPU core voltage?
It should drop until 0.65V, when board really boots.

Check U2072's I/O signals.

 

[Paul Daniels]

0V on CPU core ( 1R50 ).

PLT_RST_L going to U2072 doesn't appear to go high.

I also lose CPUCORE_PROCHOT_R_L out of U7100:46, it's there for a few seconds ( 20V 800mA->600mA ) and then is asserted low (0V).

 

[2informaticos]

Check U4760 power and signals.

 

[Paul Daniels]

All good with U4760, rails and signals being transferred one side to the other.

Might have to put this aside for a bit and look at it with fresh eyes again later.