820-3476 Green light no fan spin

[rlowe215]

Working on a 820-3476 bord, no fan spin

Measurements

PPBUS_G3H 12.62v
PPBUS_S5_HS_COMPUTING 12.63
PPBUS_S5_HS_OTHER5V 12.63v

PPVRTC_G3H 3.34

PP5V_S4 5.15v
PP5V_S0 0.219v 0.401v in diode mode

PP3V3_S0 3.3v

CPU getting hot

 

[rlowe215]

U8080 measurements

PP5V_S4 5v
P5VS0_EN 3.3v
P5VS0_FET_RAMP was shorted so replaced U8080 and short is gone

Now to the interesting. All s4 lines are gone and dont have pm_slp_s5_l

Tested to change U8080 back to the original one and all lines are back but PP5V_S0 0.219v.
Tested another new U8080 and All s4 lines are gone again.

 

[JohnB8812]

Sounds like bad U8080s to me. Remove it and check for short on FET_RAMP pin

 

[rlowe215]

already done done that, with U8080 removed no short on FET_RAMP. with new U8080 all s4 rails are gone

 

[2informaticos]

Something powered from 5V_S0 generates the problem.
Maybe CPU power supply, audio or backlight circuit.
Check first C6412/22/32/42, as common issue...

 

[rlowe215]

but dont even have pm_slp_s5_l after change of U8080

 

[2informaticos]

I bet you have a pulse.
Trigger SMC_ONOFF_L and check all PM_SLP_Sx_L signals.

 

[rlowe215]

after ultrasonic



PP5V_S0 5.16v
PP3V3_S3 3.3v
PP3V3_S0 . 3.3v

fan spin for 15 sec then stops then speed up and constant spinning


cpu getting hot

 

[JohnB8812]

So have you plugged in a screen to see if it boots now?

 

[rlowe215]

its still not booting

ppvcc_s0_cpu short to ground 0.3 ohm and 0V

 

[JohnB8812]

That's done for then RIP.

 

[rlowe215]

yes one more donor board =) Boring with this cards piled for a year.

 

[2informaticos]

Didn't check VCORE before start repair???
Diode mode on big coils, PPBUS_G3H and 3V42 are the FIRST things MUST be done when you put the board on the desk; BEFORE connecting any power!