Gigabyte ga-h81m-d2 motherboard has no reset

Gigabyte ga-h81m-d2 motherboard has no reset

Motherboard model: Gigabyte ga-h81m-d2 motherboard

Fault phenomenon: the main board has no reset

Maintenance process:

A gigabyte ga-h81m-d2 motherboard,VCC is normal, no CLK, no reset, check on time sequence, IO did not send pwork to PCH.
Check IO standby conditions are normal, check IO VIN detection, except vin0 no VCC, other VIN check VCC are normal.

Gigabyte ga-h81m-d2 motherboard without reset Figure 1.

Gigabyte ga-h81m-d2 motherboard without reset Figure 2.

Gigabyte ga-h81m-d2 motherboard without reset Figure 3.
schematic 880 is from schematic 804, and schematic 880 is from the Intel v804.

The H61 and B75 boards were repaired. The VIN of 5V and 12V detected that VCC was abnormal, resulting in io not sending pwork to the bridge.

Checking the working conditions of CPU, it is found that the CPU’s 1.75v is only pre VCC, the body is not high temperature, and the pull-up VCC vccst VCC of SVID is abnormal.

Gigabyte ga-h81m-d2 motherboard without reset Figure 4.
Considering that the bridge did not send PG to the CPU, it is speculated that the CPU that has not started may not send this VIN to detect VCC to io.
After the IO is replaced, the fault is still the same, and IO still does not send pwork to the bridge.Check schematic to judge the fault point.

Gigabyte ga-h81m-d2 motherboard without reset Figure 5.
Remove the resistance between the pwork of IO and Fuse between the bridge, and the pwork of IO is still not issued.Finally, lock the IO condition and find the fault point.

Gigabyte ga-h81m-d2 motherboard without reset Figure 6.
The gray line of ATX: atxpg VCC for IO is only 0.14v, atxpg to ground value is 56, remove Capacitor of corroded by moisture, return to 450,VCC is normal 3.3V,switch booting up.This is the end of troubleshooting.