820-3115-B No Boot

[sangolossyfon]

Board symptoms- Fan runs max speed when plugged in no matter what. But no backlight or display, no activity when USB is plugged in, even in SMC bypass. All S5-S0 5V and 3.3V rails are good so suspecting CPU failure. This one had no sign of life at all until I replaced C1768 which had broken loose from the board and now it just spins the fan. G3H voltage 13.22V, PP5VS0 5.23V, P3V3S0 3.51V. Draws 18W from wall.

 

[2informaticos]

What about CPU core voltage?
Also check PLT_RESET_L level.

 

[sangolossyfon]

CPU core voltage is 0v.
PLT_RESET_L is also 0v.

 

[2informaticos]

Which big coils get voltage?

 

[sangolossyfon]

I actually re-measured CPU core voltage and the PLT and they were 1.15v and 3.3v respectively. While USB ports do get power there is no usb activity.
Coils-
L7030- 13.5/14v
L7630- 1.1/7.5v
L7100- 0.8/1v
L9701- 2.5/3.5v
L7520- 8.8/1.1v
L7510- 4.4/1.1v
L7260- 5.4/6.4v
L7220- 3.5/3.8v
L7330- 1.6/1.6v
Only coil with 0v was 7550, 0v on both sides.
The cpu does get a bit warm.

 

[2informaticos]

CPU core should drop from 1.1V to 0.7V aprox, when board boots.
There may be a communication problem between PCH, CPU and BIOS.

BTW, stop checking DC voltage on any coil's input pin.