Asrock 970 PRO3 - missing 1.1V on NorthBridge

[kotel studios]

Hi,

Recently I got this Asrock 970 PRO3 board from scrap. It had a few missing caps under the NB which I've replaced. Sadly, one of them went short (NC597 from boardview file). I did replace it and there doesn't seem to be any shorts left, but the board is not executing POST nor beep codes. I once got it to POST after I was slightly bending it, but that was only once. I tried to redo the same steps but to no avail. All caps on the backside of NB have 22-ish ohms.

I have traced the problem to an dead Northbridge VRM. There's no voltage on Phase (pin 8), FB (pin 6), UGATE (pin 2) and LGATE (pin 3). There's VCC and 0.8v on COMP/EN (pin 7). No voltage besides on the tabs of the two MOSFETs.

I do not know whether it's a shorted NB or dead VRM, so I'd like to ask for help during troubleshooting.
I have double checked each component and trace for any obvious damage and there wasn't anything that seemed to be damaged. And yes, that trace repair under the SB is crap, but it made the RESET line work correctly now.

[kotel studios]

After removing the coil from the NB VRM I measured 0.22V no load on the output. Sadly, even with an 1K resistor as load the whole VRM shuts down. The values of each pin of the RT8120B (datasheet) changed too:
before / after (removal of coil)
BOOT: 12V / 12V
UGATE: 0.03V / 0.19V
LGATE 0.45V / 0.45V
PHASE: 0.03V / 0.19V
COMP/EN: 1.1V / 1.11V
FB: 0.03V / 0.03V
VCC: 12V / 12V

For clarification, 22ohms on caps was before I started replacing the caps and before the capacitor failure.

North bridge draws too much current from my benchtop PSU (on 600mA the voltage is 0.7V) which might point to internal short of the NB, but then why would the VRM be so funky? Collateral damage of the capacitor going short?

Any ideas?