If your PC won’t turn on but motherboard light is on, remove all input and output peripherals, RAM, hard drive, and fan connector try to turn on. If it does not work, reinstall the CPU properly. Not getting a response from the system at all, try to reseat all the components of the system. Otherwise, read the article below.
The way to fix PC won’t turn on but motherboard light is on
Motherboard: If reseating all the components cannot fix your problem, I would recommend you to replace the motherboard. Because sometimes bad motherboard causes the problem.
Power Supply Unit (PSU): You can test your PSU to another working PC. If the PC works fine, the problem is with other parts of your computer.
Otherwise, Disconnect the PSU to test if the voltage supply is out of range. Then, use a paperclip to short between the green wire and one of the black neighbor black wire to turn on the PSU. If the test cannot pass, it is dead. Otherwise, reconnect DMM to the back of the main power plug.
Memory: The memory might be non-ECC, bad, faulty, or incompatible. So, you should test it. Follow the guide shown in Step 2.
Boot: Try to boot with the motherboard, CPU, one RAM module in one slot, and the cooling system.
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