BIOSTAR th61 motherboard does not run code

Motherboard model: BIOSTAR th61 ver: 6.0

Fault phenomenon: the motherboard does not run out of code when it is turned on

Maintenance process:

A BIOSTAR th61 ver: 6.0 motherboard, the fault is that the motherboard does not run the code when it is turned on, and it does not run the code from time to time. After a period of power failure, it does not run the code again.There is no solution to the BIOS.

BIOSTAR th61 motherboard does not run out of code Figure 1.
It is measured that the whole board VCC is normal, and the memory conditions are also satisfied, that is, the set display of VCC does not cause code run out.
Run set display VCC up and down tube drive pin to pu6 chip.

BIOSTAR th61 motherboard does not run out of code Figure 2.

BIOSTAR th61 motherboard does not run out of code Figure 3.
pin is connected to pu pin V, and the power supply of the display chip is pu pin, and the power supply of the display chip is c1431.

BIOSTAR th61 motherboard does not run out of code Figure 4.
It is found that pu1 chip has an envgt pin. The voltage of 12V VCC is 3.0V through pr56 (3K) and pr60 (1K). The measured voltage is 1.8V, which is obviously abnormal.When the resistance was removed, it was found that pr56 diode value was too large = 5.6k.

BIOSTAR th61 motherboard does not run out of code Figure 5.

BIOSTAR th61 motherboard does not run out of code Figure 6.
Unable to find a suitable resistance diode value, add a color ring resistor.Boot code running is normal.