820-3115 p3v3s5_en_l

[arghhh]

820-3115 no power, no PP3V3_S5.

Q7221 pin 2, 5 are 3.4v, which means the U7200 entrip will not enable the PP3V3_S5 regulator.

However, I cannot figure out for the life of me how U7941 drops P3V3S5_EN_L. Is it internal? So when SMC_PM_G2_EN is present on pin 2, then U7941 will set the output P3V3S5_EN_L on pin 4 to low?

 

[ALB-Repairs]

Whats the Voltage on R7273?

 

[dukefawks]

Is SMC_PM_G2_EN even present?

 

[arghhh]

Will check and yes.

 

[dukefawks]

If G2 is high and the output of U7941 is not low then check power to pin 1 U7941 or it may be dead. U7941 simply inverts the signal from pin 2 to 4.

 

[larossmann]

When SMC_PM_G2_EN is present on U7941, then U7941 is supposed to make P3V3S5_EN_L_R low, which after R7941, should be 0v as P3V3S5_EN_L.

If P3V3S5_EN_L is high, then P3V3S5_EN is not present - because the _L means the signal is asserted when it is "low", in this case, 0v. "P3V3S5_EN" means enable pp3v3_s5 rail, so P3V3S5_EN_L must be 0v for this to occur.

SMC_PM_G2_EN will go through U7941 which makes it high for P5V3V3_REG_EN - which has to be 3.3v for PP5V_S5 to be created, and low for P3V3S5_EN_L, which has to be 0v for PP3V3_S5 to be created.

 

[arghhh]

Replaced U7941 twice and P3V3S5_EN_L was still high. U7941 had 3.42v on vcc. Shorted out C7942 though and the fan spins... Any ideas?

 

[dukefawks]

G2_EN must not be high then, there is nothing more to this really. You can remove R7941 and see if one of the pins is being pulled high.