820-00840 no fan spin, no boot.

[Sr. Robot]

Hi, got an 820-00840 that doesnt not boot nor fan spin, no signs of visible damage.

PPBUS_G3H: 13v

PP5V_S5 is erratic between 2 and 5v

PP3V3_G3H: 3.4v

PP3V3_S4: 0v

PP1V8_S3: 0v

 

[2informaticos]

You must get 3V3/5V_S5 stable first.

Did you check the board alone on the desk?

 

[Sr. Robot]

Yes i measured it alone on the desk. At several points but its the same, its jumping from 2 to 3 to 4 and 5v

 

[Sr. Robot]

S5_PWRGD is also jumping around

 

[2informaticos]

Remove R7661 and tie C7663 to ground.
Check 3V3/5V_S5 behavior then.

 

[Sr. Robot]

No change

 

[2informaticos]

Now do the same for R7662 and C7668 pads.
Check if 5V_S5 gets stable.

 

[Sr. Robot]

Now PP5V5_S5 PP3V3_S5 are both stable 0v

 

[2informaticos]

Strange, 3V3_S5 should be 0V when P3V3S5_EN is tied to ground.

Check diode mode to ground on all big coils; compare with good board.