820-2838 not turn on

Mellerv89

New member
The MagSafe has green light and fans spinning, but no screen and chime.

PP0V9_ENET and ALL_SYS_PWRGD 1.8v are to low. Where can I find the reason for this? Because all the input voltages are right?

PP5V_S0 5.08v
PP3V3_S0 3.3v
PP1V5_S0 1.51v
PP1V05_S0 1.05v
PP1V05_S0_MCP_PLL_UF 1.05v
PPVCORE_S0_CPU 0.99v (1.25v)
PPVCORE_S0_MCP 0.93v (1.05V
PPDDRVTT_S0 0.68v (0.75v)

PP3V3_ENET 3.3v
PP0V9_ENET 0.29 (0.9V)

SMC_PM_G2_ENABLE 3.3v
PM_SLP_S4_L 3.3v
PM_SLP_S3_L 3.3v

ALL_SYS_PWRGD 1.8v

C7990 had corrosion. Cleaned it but not replaced.
 

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dukefawks

Administrator
ALL_SYS_PWRGD is the first issue to tackle here. Only thing I can say is look at schematic how it is generated. All S5 S3 and S0 voltages must be there for it to go high. Look at U7870 and all the power good lines that come together there. One must be pulling it low.
What is the resistance to GND on the ALL_SYS_PWRGD line?
 
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