A1398 820-00426 no power

[hgoncalves]

Hi.

I have an A1398 820-00426 with no power.

PPBUS_G3H is shorted. I already lifted F7140/41 and F7700, and PPBUS_G3H is shorted (0.002 on diode mode, and 0.5 ohms to ground).

No big coils seams to be shorted.

I've already injected 3V on PPBUS_G3H, I get around 2A of consume but I can't see anything hot in the thermal cam.

Shall I go higher on voltage, or is there any better way?

 

[2informaticos]

First remove CPU heatsink.
Did you check for short at L7095 too?

If you really got 6W (2V/3A), IR camera should show something.
If for sure no short on any secondary power supply, then increase the voltage slowly.

 

[hgoncalves]

HI.

After increasing the voltage, U7310 was getting hot, and after replacing it, now PPBUS_G3H is OK, and I have 12.53V there.

However, still no power on.

PP5V_S5 = 5V
PP5V_S4 = 0V

PP3V3_S5 = 3.3V
PP3V3_S4 = 0.427V

Can it be Q8000?

Tks.

 

[2informaticos]

CPU is probably dead; overvoltage occured through U7310...