820-3437-B not powering

[chrislewis85]

Hi guys,

Got a 3437-B which had fluid damage around U1950. Cleaned area and replaced U1950. Getting green light but no fan spin. Rails so far as follows:

PPBUS_G3H = 8.56V
PP3V3_S5 = 3.0V
PP5V_S5 = 5.0V
PP3V3_S4 = 0V

Struggling to understand on schematic where S4 rails will come from - and is the S5 rail being lower than 3.3V relevant (only 3.0V)?

 

[2informaticos]

You may have corrosion around U7501.
Post diode mode to ground at L7560.

Do you get 3V3_SUS?

 

[chrislewis85]

Diode mode to ground at L7560 = 0.344v

3v3_SUS is 0v

U7501 looks clean (but also fresh solder on test points in the area so likely board has been repaired previously)

 

[2informaticos]

Check S5_PWRGD, PM_DSW_PWRGD, PM_BATLOW_L, SMC_ADAPTER_EN and all PCH's RTC signals.