Asus Z97-AR mainboard Won't Turn On repair

Asus Z97-AR mainboard Won’t Turn On repair

Main board model: ASUS Z97-AR main board

Symptoms: motherboard Won’t Turn On

Maintenance process:

An ASUS Z97-AR motherboard, plug-in standby light is on,short-circuit Switch does not respond no power on.

Measured according to no power on, 3VSB is normal, DPWROK/RSMRST# 3.3V is normal, SLP_S3# 3.3V is normal, and 0.0V after O_PSON#Switch switch.

Asus Z97-AR motherboard Won’t Turn On repair figure 1.

Looking at Boardview, it is found that there is an MOSFET(O2Q1) between 0_PSON# and ATX socket, which is MOSFET of N-channel. When measuring G pole, there is no VCC, and there is no conduction between 0 _ pson # and ATX socket, which indicates that switch condition is missing.

Asus Z97-AR motherboard Won’t Turn On repair figure 2.

G pole signal name O2_CUT_PSON# of MOSFET(O2Q1) comes from EC(O2U1), and EC chip on motherboard is involved in startup timing, adjustment of VCC and fan control. Measuring no waveform of BIOS 1 pin of EC with oscilloscope shows that EC chip is not working and O2_CUT_PSON# cannot be sent.

Asus Z97-AR motherboard Won’t Turn On repair figure 3.

Test the working conditions of EC chip: 1.VCC 2.CLK 3. Reset 4. Procedure

VCC is 3VSB normal;

Measured at 32.768MHz CLK, no vibration.

Asus Z97-AR motherboard Won’t Turn On repair figure 4.

Measure Crystal,pin Diode value is normal, replace Crystal and resonant Capacitor, and then measure the waveform.Crystal waveform is perfect, but it still can’t be switch, and measure the 1 pin chip selection or no action of EC BIOS!

Asus Z97-AR motherboard Won’t Turn On repair figure 5.

The reset O2_RSMRST# 3.3V is normal, and it is suspected that there is something wrong with EC program. Prepare to brush BIOS, remove EC BIOS, and type BIOS PAD diode value. It is found that BIOS 2 PAD 24301O2 _ SPI _ miso _ R PAD 18401 PAD 22601 is obviously too large. 1 pin is 660 to ground diode value, 2 pin is 800 to ground diode value, and normal SPI 4 lines are similar to ground diode value. Obviously, there is something wrong with 2 PAD 24301 lines.