ASUS B85-PRO GAMER has reset without missing code for repair

ASUS B85-PRO GAMER has reset without code running, short circuit the C and E poles of SQ35, reset the PWROK signal of the bridge, and replace the SQ35 with code running light.

Machine model: ASUS B85-PRO GAMER

Fault phenomenon: code does not run when resetting

Maintenance process: Sometimes the trigger is normally powered on without code running, sometimes it is triggered with power loss like lack of CPU power supply. The fan turns once and cycles for three times before power loss, but the code does not run. When the trigger is normally powered on, the voltage of the whole board is normal, the power supply inductance and MOS tube waveforms are normal, the PCIE clock is normal, the PCIE A11 pin resets, the PLTRST is normal, the CPURST comes out, and the oscilloscope pokes the CS # pin of the BIOS sometimes with a pull-down waveform, I brushed a BIOS, but it didn’t work.

Properly reset and do not run the code. According to previous experience, we decided to measure the PWROK signal of the bridge.

ASUS B85-PRO GAMER has reset without missing code for repair Figure 1.

Measure O according to the test points in the maintenance guide_ The PWROK signal voltage is 3.3V. Open the point and check the connection.

ASUS B85-PRO GAMER has reset without missing code for repair Figure 2.

O_ The PWROK is also connected to the SQ35, and the other end of the SQ35 enters the PWROK of the bridge.

ASUS B85-PRO GAMER has reset without missing code for repair Figure 3.

Measure that the SQ35 control pole has a normal high level when it is in standby. After triggering, it becomes low and set to high O_ PWROK signal, this process seems to be OK. However, according to past maintenance experience, during the process of triggering the power on of the main board until the code runs out, (including manual reset and needle reset, and restart in standby mode). The PWROK signal of the bridge has a high and low reset process, but many mainboards lose power when poking this signal with a multimeter, which is difficult to detect.

So I used tweezers. When it was powered down three times, and the fourth time it was not powered down, I used tweezers to short circuit the C and E poles of the SQ35. The small light on the diagnostic card immediately responded, and then the code ran out. The horn made a drip sound. The code still does not run when it is triggered after shutdown. So the old trick was repeated. The PWROK signal of the bridge was reset manually, and the code ran out.

So the SQ35 was replaced, the code ran off and the machine was lit, and the display card continued to be installed, and everything was normal all afternoon.