There can be a case when you encounter a problem, like a desktop motherboard is powered on, but no display is coming.
So below, we will see step-by-step [solutions for the desktop motherboard power-on problem, which is the most common problem while repairing a desktop motherboard at the chip level.
Step 1. Check Physically any capacitor or chip blown
Do a physical inspection to check if any capacitor or chip is blown out. Mostly, a capacitor or MOSFET gets burnt out or increased in shape. These are called faulty capacitor conditions. In that case, replace that capacitor.
Step 2. Repalce RAM or CPU and Check
The second check is the motherboard by replacing the RAM or CPU with another RAM or CPU of the same type. If the motherboard starts and gives output in this test, your CPU or RAM is faulty.
Step 3. Heat the Motherboard And Recheck
In the third step, heart your motherboard with a BGA machine or OVEN. After heating, let the motherboard cool down. Finally, check the motherboard for working. One note, though: don’t check the motherboard board while it’s super hot; let him cool down a bit.
Step 4. Check RST Light / RESET Signal Blink
The fourth step involves checking the blink in the KQCPET6 Debug Card. You should check it when you power on the PC. The RESET signal should blink only once.
Step 5. Check CLOCK SIgnal Glow
For the fifth step, you will check after pressing the power button whether the CLOCK light is glowing or not in the debug card. If it’s not glowing, then check for a 25 MHz crystal or PCH.
Step 6. Check the FRAME LED light
On debug, card check for FRAME LED light blick when you power on. If it’s not blinking, then flash bios.
Flashing the BIOS should solve your problem. If flashing the BIOS on your Desktop does not give you a display, then replace the CPU and recheck.
If even though replacing the CPU, the PC does not give a display, then finally replace PCH.
Step 7. Whether Run LED Light Is Glowing
Check whether the RUN LED light is glowing after powering on the PC. If it’s not glowing, flash the bios.
Flashing the BIOS should solve your problem. If, after flashing the BIOS, your Desktop does not display, then replace the CPU and recheck.
If even though replacing the CPU, the PC does not give a display, then finally replace PCH.
Step 8. Refer to the Code On the Debug Card
Check for the code generated according to the BIOS type. Some standard codes on debug cards are given below.
NO – It means the CPU is not able to access the BIOS.
00 / FF – It means BIOS is not readable
01/ 02 – CPU may be faulty
C1 / D1 – RAM suspected faulty
Desktop Motherboard Power Display Signals & Their Description
The following are Signals and their description for the desktop motherboard to turn on the PC.
Signal Description
ATX PWR OK SMPS sends a power ok signal from Gray wire saying SMPS power stable.
SYS_PWROK VRM chip generates this signal when CPU CORE VOLTAGE is stable. This signal goes to PCH.
PFMRST PCH generates a signal called platform reset, which resets the entire motherboard. We can check this signal at PCI EXPRESS slot 3 Volts.
CPURST CPU gets the rest 1 Volt signal.
CPUWROK PCH sends this signal to the CPU, saying the CORE voltage is stable.
DRAM_RESET CPU sends this signal to DDR and resets RAM.
CLOCK PCH generates different clock frequencies for the entire motherboard by using a 25MHz crystal.
BIOS CS & RD Pin PCH access BIOS pin no one chip select and PIN read pin.
FRAME Communication occurs between CPU and PCH via the DMI bus, generating that time frame signal.
RAM SM BUS Power-on self-test takes place. PCH checks all devices via SM bus. First, it checks the RAM SPD chip via the SM BUS clock and data.
RAM CLK CPU starts communicating with RAM, sending clock signals.
DMI BUS DMI bus gets active.
DISPLAY SM BUS When everything is done, PCH communicates the display RGB port via SM Bus while it checks that the display output is preset.
FDI BUS CPU sends graphic information to PCH via the FDI bus.
RGB OUTPUT PCH sends RGB H sync and V sync signals to the monitor.
So below, we will see step-by-step [solutions for the desktop motherboard power-on problem, which is the most common problem while repairing a desktop motherboard at the chip level.
Step 1. Check Physically any capacitor or chip blown
Do a physical inspection to check if any capacitor or chip is blown out. Mostly, a capacitor or MOSFET gets burnt out or increased in shape. These are called faulty capacitor conditions. In that case, replace that capacitor.
Step 2. Repalce RAM or CPU and Check
The second check is the motherboard by replacing the RAM or CPU with another RAM or CPU of the same type. If the motherboard starts and gives output in this test, your CPU or RAM is faulty.
Step 3. Heat the Motherboard And Recheck
In the third step, heart your motherboard with a BGA machine or OVEN. After heating, let the motherboard cool down. Finally, check the motherboard for working. One note, though: don’t check the motherboard board while it’s super hot; let him cool down a bit.
Step 4. Check RST Light / RESET Signal Blink
The fourth step involves checking the blink in the KQCPET6 Debug Card. You should check it when you power on the PC. The RESET signal should blink only once.
Step 5. Check CLOCK SIgnal Glow
For the fifth step, you will check after pressing the power button whether the CLOCK light is glowing or not in the debug card. If it’s not glowing, then check for a 25 MHz crystal or PCH.
Step 6. Check the FRAME LED light
On debug, card check for FRAME LED light blick when you power on. If it’s not blinking, then flash bios.
Flashing the BIOS should solve your problem. If flashing the BIOS on your Desktop does not give you a display, then replace the CPU and recheck.
If even though replacing the CPU, the PC does not give a display, then finally replace PCH.
Step 7. Whether Run LED Light Is Glowing
Check whether the RUN LED light is glowing after powering on the PC. If it’s not glowing, flash the bios.
Flashing the BIOS should solve your problem. If, after flashing the BIOS, your Desktop does not display, then replace the CPU and recheck.
If even though replacing the CPU, the PC does not give a display, then finally replace PCH.
Step 8. Refer to the Code On the Debug Card
Check for the code generated according to the BIOS type. Some standard codes on debug cards are given below.
NO – It means the CPU is not able to access the BIOS.
00 / FF – It means BIOS is not readable
01/ 02 – CPU may be faulty
C1 / D1 – RAM suspected faulty
Desktop Motherboard Power Display Signals & Their Description
The following are Signals and their description for the desktop motherboard to turn on the PC.
Signal Description
ATX PWR OK SMPS sends a power ok signal from Gray wire saying SMPS power stable.
SYS_PWROK VRM chip generates this signal when CPU CORE VOLTAGE is stable. This signal goes to PCH.
PFMRST PCH generates a signal called platform reset, which resets the entire motherboard. We can check this signal at PCI EXPRESS slot 3 Volts.
CPURST CPU gets the rest 1 Volt signal.
CPUWROK PCH sends this signal to the CPU, saying the CORE voltage is stable.
DRAM_RESET CPU sends this signal to DDR and resets RAM.
CLOCK PCH generates different clock frequencies for the entire motherboard by using a 25MHz crystal.
BIOS CS & RD Pin PCH access BIOS pin no one chip select and PIN read pin.
FRAME Communication occurs between CPU and PCH via the DMI bus, generating that time frame signal.
RAM SM BUS Power-on self-test takes place. PCH checks all devices via SM bus. First, it checks the RAM SPD chip via the SM BUS clock and data.
RAM CLK CPU starts communicating with RAM, sending clock signals.
DMI BUS DMI bus gets active.
DISPLAY SM BUS When everything is done, PCH communicates the display RGB port via SM Bus while it checks that the display output is preset.
FDI BUS CPU sends graphic information to PCH via the FDI bus.
RGB OUTPUT PCH sends RGB H sync and V sync signals to the monitor.