Repairing PC Chips M570

[Rainbow]

Something new about my dead M570:
I took an old multimeter and found that there's no 3.3V power. Only about 1V instead of 3.3V on AGP, DIMM slots and near the TAG RAM (3.3V or 5V with 0ohm). The north bridge runs on 3.3V so this looks to be the problem.
With ohmmeter, found that 3.3V on DIMMs, AGP, TAG RAM are connected together. There's some transistor(?) that's connected with this too (Lintek LV1084 - Q5 near BIOS). The ohm-meter also shows that 3.3V output from ATX power connector is not directly connected to the 3.3V on AGP... I guess that it goes through some regulator (because the board has also AT power connector which does not provide 3.3V) - but where?

[Rainbow]

Connected 3.3V from ATX power connector to A16 pin of the AGP slot. Board works, but not with AT supply.
Does anyone know how the regulator should work?