Jijia B75 has no reset and no signal repair

Jijia B75 No Reset No Signal Detection Pin Capacitor Short Circuit Blowing off C3 Capacitor Power-on Display.

Machine model: Jijia B75

Fault phenomenon: no reset, no signal

Maintenance process: repair a gigabyte B75 motherboard, measuring memory VCC 1.5V, bridge VCC 1.05v, 1.8V normal, VTT pwrgd 1.05v, CPU on, no CPU VCC.According to the H61 timing sequence, CPU VCC is pre VCC at 0V, and CPU VCC will not output until all VCC signals are normal.The reset on PCI slot and CLK are not found, indicating that the circuit is abnormal.

According to the characteristics of Gigabyte it8728, the premise of sending IO pwrok is that the circuit VCC on the main board is normal, and the 12V and 5V of 127 and 128 on the IO pin are detected, and the IO pwrok will be sent out only when the pin is detected to have 2V, and the rear axle will send out CLK signal.

Jijia B75 has no reset and no signal repair Figure 1 .

When measuring 12V pin, i.e. there is no VCC in the 127 pin of IO, a problem is found. After that, C3 Capacitor Short circuit on 12V detection circuit is detected, resulting in 12V detection pin VCC being 0V.Blow off C3 Capacitor, power on display, troubleshooting, maintenance is over!