820-3437 no fan, pulsing

VinceLx

Member
The board looks ok, no fan, power supply gives 20-30mA with pulses at 120mA every 3-4 seconds as if it wanted to start but cannot

PP3V42_G3H=3.44V
PPBUS_G3H=8.6V

PP5V_S5=5V
PP3V3_S5=3.3V
PP3V3_SUS=3.3V

PP5V_S4=bursts every 3-4 seconds no readable
PP3V3_S4=bursts every 3-4 seconds at 3.3V
SMC_S4_WAKESRC_EN=0V

PP1V2_S5_SMC_VDDC=1.2V
SMC_BC_ACOK=3.4V
SMC_RESET_L=3.4V

What should I check next?
 

VinceLx

Member
In SMC bypass mode: PPBUS_G3H=8.2V, the fan is spinning half a second, then quarter fan spin, and it starts again half a second, then quarter fan spin... Sometimes the fan is just ticking.

I have pulses on L7520, L7630, L7430, L7310, L7320
No pulses on L3095
3.3V on L7560, 8.2V on L7130
 

VinceLx

Member
Q8150 removed, pulse of 3.4V on ALL_SYS_PWRGD, exactly same behaviour in SMC bypass mode, fan is spinning half a second, then quarter fan spin, and repeat
 

2informaticos

Administrator
Staff member
Could be bad CPU, or just broken/corroded resistor.

Check all SPI Bus Series Termination resistors and their traces.
 
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