820-00840 no turn on

[Sr. Robot]

820-00840 with 13v on ppbus.

PP5V_S5 starts at 0.4v and then drops to 0v (no pulsing).
PP3V3_G3H = 3.4v
PP3V3_S4 = 1.1v

L7670 is pulsing and L7030 is stable 0.9v

 

[2informaticos]

Any history available?

Check in diode mode all secondary power supplies.

 

[Sr. Robot]

No history available, PP3V3_S0 is shorted 0.4 ohms to ground.

Injecting 3v and 1amp heats nothing. Voltage drops to 0.5v

 

[2informaticos]

How voltage drops to 0.5V, if you inject 3V???
As I always said, set amp limit to max first!!!

 

[Sr. Robot]

C2976 was shorted. The short is now gone and C2976 replaced. Still no PP3V3_S0 and no PP5V_S5. Could not find any other short in secondary lines

 

[2informaticos]

L7670 still pulsing?

Post U7650 basic volatges: 23, 22, 12, 13, 29, 21, 4.

 

[Sr. Robot]

L7670 is now stable 0.6v.

U7650

23 = 13.01v
22 = 0v
12 = 0v
13 = 0v
29 = 0v
21 = 0v
4 = 0v

smc bypass does nothing

 

[2informaticos]

Check PMIC LDOs.

 

[Sr. Robot]

PP3V3_LDO3V = 3.3v
PP5V_LDO5V = 5.1v
BANJO_FBLDO1 = 0v

 

[2informaticos]

1V25_VREF nothing?

Also check 3V1_RTC.

SMC_PM_G2_EN present?
PMIC_SHUTDOWN_L stays high?

 

[Sr. Robot]

1V25_VREF = 1.25v
3V1_RTC = 3.1v
SMC_PM_G2_EN = 3.4v
PMIC_SHUTDOWN_L= 3.3v stable

 

[2informaticos]

Check U7890 voltages.

 

[Sr. Robot]

SSD_PWR_REQ = 0.4v
PMIC_EN_P3V3S5 = 0v
PM_EN_PVXS5 = 0v
PP3V3_G3H = 3.4v

PMIC_PGD and PM_EN_P3V3S4 are also 0v

 

[2informaticos]

Check if R7883 is good.
You may need to change U7800...

 

[Sr. Robot]

R7883 is good

Any chance is not the SMC? i dont have donor board for this model

 

[2informaticos]

You should change U7800 first...