Verify power connections

1. Make sure the power supply is turned on. If it’s turned on already, turn it off and unplug it from the pc and the outlet(make sure there are no safety mechanisms on the cable before pulling).

2. Inspect the cable for damage. If it’s been folded for a long time, or the shielding is ripped, the cable should be replaced, and kept in a way that it doesn’t stay folded, but rather coiled, if possible, so the shielding and internals remain intact over long periods of time.

3. Make sure the outlet is working by testing it with another device.

4. Make sure the power cable is firmly connected to the PC and the wall outlet.

Remove and Reconnect Internal Power Cables

1. Turn off the power supply before unplugging everything from the back of the pc.

2. Open the PC case.

3. Reseat the 24-pin motherboard power connector.

4. Reseat the 8-pin CPU power connector (usually near the CPU).

5. If using a GPU, reseat the PCIe power cables.

Resuscitate 

1. With the pc plugged in, and the PSU turned on, press the power button for 60-65 seconds

2. Try booting again.

Reset CMOS

1. Power off the PC and unplug it.

2. Remove the CMOS battery (silver coin-cell) for 30 seconds.

3. Reinsert the battery and reconnect power.

4. Try booting again.

Test the RAM

1. Remove all RAM sticks.

2. Insert a single stick into the primary slot (usually slot 2).

3. Try booting.

4. Repeat with each stick to isolate faulty memory.

Test with Minimal Hardware

Disconnect everything except:

• Motherboard
• CPU
• One stick of RAM
• Power supply

Try to power on. If it works, reattach components one at a time to find the failed part.

Seek Professional Repair (If All Else Fails)

If the PC still shows no signs of power or signal, a technician may need to check for:

• Faulty voltage regulators

• Short circuits

• Burnt or damaged components.