Gigabyte B85M-D2V 3.0 does not trigger repair

Gigabyte B85M-D2V 3.0 does not trigger. Replace the IO and repair the fault.

Machine model: Gigabyte B85M-D2V 3.0

Fault phenomenon: no triggering

Maintenance process: The colleague took a motherboard and asked for help. He said that the bridge might be broken. Let me see if I can save it.

After getting the mainboard, pressing the switch did not respond. The 2.56V measuring switch pin was obviously abnormal. Continue to measure the 1117 5V produced by the standby 3.3V, and the normal output was 2.56V. The normal output should be 3.3V, but the 1117 could not be broken!

Gigabyte B85M-D2V 3.0 does not trigger repair Figure 1.

It is still the same when removing one from the material plate and replacing it with another, that is, there is a problem with the rear stage. Disconnect the parts that are in contact with the standby 3.3V one by one. In addition to the bridge, 2.56V is still the same for half a day. I have decided that the bridge is broken, but I still don’t give up. Connect voltage regulator 3.3V to 1117’s 3.3 output pin.

Measure 0.25V of the starting pin again, but measure 3.3V at one end of R172 and 0.25 at the other end, which is completely different from the previous one. That means there is no problem with the bridge. Then why is the output of 1117 not 3.3V? Cut off the power and replace the two electrical groups NR176 NR180 connected to 1117 that have a 2pin partial voltage. Power on the test and the output is 3.3V, but the switch pin is still 0.25V. Continue to remove the IO. The switch pin 3.3V is normal, the IO is broken, and the feed plate is replaced, triggering the startup and lighting up, Here’s the fix.