820-3115-B green light, no boot

[Sr. Robot]

Hi, got an 820-3115-B with green light, no boot

PPBUS_G3H: 12.53 v

PP3V42_G3H: 3.47v

PP5V_S5: 0v

PP3V3_S5: 0v

Diode mode to ground PP5V_S5: 0

U7200 is getting hot, but removing it does not take the short away. Near caps arent getting hot.

 

[2informaticos]

Remove L5800, R5805 and check again.
Also check C7273 and C5800.

Don't forget U/C7801.

 

[Sr. Robot]

U5805 was shorted.

Now i have fan spin, HDD light but no image and no chime.

Now i have every rail but PPVCORE_S0_CPU (0v)

 

[2informaticos]

ALL_SYS_PWRGD goes high?

 

[Sr. Robot]

Yes, ALL_SYS_PWRGD is 3.3v

 

[2informaticos]

Post U7400 voltage; 19, 29, 46, 47, 1, 48.
Check R7402/03.

 

[Sr. Robot]

1. CPUIMVP_TONB: 0.5v
19. PP5V_S0: 5.0v
29: PP5V_S0: 5.0v
46. PP5V_S0_CPUIMVP_VCC: 5.0v
47. CPUIMVP_VR_ON: 4.57v
48. CPUIMVP_TONA: 0.6v

R7402/03 values are spot on

 

[2informaticos]

Are you sure to have 4.57V at ALL_SYS_PWRGD???

 

[Sr. Robot]

No, ALL_SYS_PWRGD is 3.3v

 

[2informaticos]

And what difference do you see in schematic between ALL_SYS_PWRGD and CPUIMVP_VR_ON???

 

[Sr. Robot]

Sorry, i measured wrongly. CPUIMVP_VR_ON is also 3.3v

Replaced Q7950 just in case, no change.

 

[2informaticos]

Just in case, change U7400.
What is the resistance to ground (ohm scale) at L7510/50?

 

[Sr. Robot]

Replaced U7400, no change.

L7510: 3,5 ohms

L7550: 2.5 ohms

 

[2informaticos]

Be sure all surrounding resistors and traces are good.
Try known good BIOS.

 

[Sr. Robot]

Resistors look good, traces are good.

Tried working BIOS no change.

 

[2informaticos]

Then bad CPU, or PCH...