GIGABYTE GA-H61M-DS2 DVI motherboard startup fan will stop Restart repeatedly for repair after one turn

Main board model: GIGABYTE GA-H61M-DS2 DVI main board

Malfunction: the motherboard startup fan will stop once it turns.

Maintenance process:

A piece of GIGABYTE GA-H61M-DS2 DVI motherboard,switch has no display, the fan turns for two seconds to stop, and it is automatically powered on again, and then repeated after two seconds.

GIGABYTE GA-H61M-DS2 DVI motherboard startup fan will stop Restart repeatedly repair after one turn Figure 1.

Measured fan speed, CPU VCC.1.1V, memory 1.5V, bridge VCC are all normal, and VCC is not displayed. Brush BIOS first, no results, it is determined that auto power off Restart repeatedly is caused by the lack of VCC on the motherboard. Check VCC, CPU _ VTT 1.05 V, VCCSA 0.95 V, VTT _ PWRGD 1V again carefully, and they are basically normal.

Check the abnormal signal of PCH_VRMPWRGD, and find the component location map. The measured results are as follows:

GIGABYTE GA-H61M-DS2 DVI motherboard startup fan will stop Restart repeatedly repair after one turn Figure 2.

PCH_VRMPWRGD is 0V, which should normally be 3.3V
0.6V for DQ17 2 pin and 0V for 3 pin.
1.1V for DQ16 2 pin and 0.6V for 3 pin.
To sum up, DQ16 2 pin is high level, this tube should be on state, and 3 pin should be 0V under normal state. At this time, it is 0.6V, which is not normal.

Because DQ17 is controlled by DQ16, and DQ17 2 pin is 0.6V, the tube is turned on, which causes the pull-up VCC 3.3V of 3 pin to be pulled down, so CH_VRMPWRGD has no VCC.

GIGABYTE GA-H61M-DS2 DVI motherboard startup fan will stop Restart repeatedly repair after one turn Figure 3.
Replace DQ16 directly.

GIGABYTE GA-H61M-DS2 DVI motherboard startup fan will stop Restart repeatedly repair after one turn Figure 4.
Measure PCH_VRMPWRGD to be 3.3V again, and the fan runs wildly all the way,Normally booting up, troubleshooting.