820-2936 won't turn on(hasgreen light) no liquid damage

[bighead]

Hi,

I received this macbook with not turning on issue.
No liquid damage. The board was pretty dusty. But no sing of liquid damage.
When I press the power button the fan spins up a little bit and that's it. It does not do the on-off loop.

Here are the measurements:

PPBUS_G3H 12.57V
PP3V3_S5 3.3V
PP5V_S5 5V
RTC_G3H - 3V
32kHz present
Y25010 oscillates

Looks like when I hit the power button every power rails are coming on except: CPU_VCORE.

Checked U2800 and Y2805. Y2805 does not oscillate. I changed both Y2805 and U2800.

What could this be?

Thank you.

 

[aprendiz]

Did you check RTC signals to PCH??, R1800 to R1803, should be about 3V on PCH side... Also could be a short on PP5V_S3 line....... Could be C6521, shorted USB port...

 

[bighead]

Yes, I checked RTC signals. I forgot to mention it in my first post. No short on PP5V_S3 over 20k ohm.

Edit:
I've also
PP3V3_SUS - 3.3V
PP1V05_SUS - 1.05V

 

[dukefawks]

If no liquid I would try BIOS first. Backup the old!!

 

[bighead]

Definitely no liquid damage. I tried different BIOS, but same thing. I've two same non-working board here for parts. I also tried those BIOS on this board. Nothing changed.