Diagnose a dead power supply unit (PSU) – What to do when a PC power supply fails

Corsair VS550 power supply unit (PSU)
Corsair VS550 power supply unit (PSU)


“Sir, I need help.. My PC is not working.”

– Please provide its make and model and describe what is wrong with it.

“My PC is not starting at all. Nothing comes on.”


The cause could be a faulty power cable or mains socket, a dead power supply unit (PSU), bad RAM memory, a dead motherboard, etc Therefore, it could be free and easy to fix or difficult and costly. You are lucky if the cause is a faulty cable or dead PSU.

There are plenty of videos on YouTube that show how to diagnose and fix a dead computer.

Here is one of them –

Troubleshoot A Dead Computer – PC No Power – Easily Fix A Dead PC –

Take care if you try using the paper-clip method of testing the power supply unit, as demonstrated in the first video.

Here is another good video on this problem:

Dead PC Diagnosis and Repair –

Note that you must NEVER open up a power supply unit to try and fix it yourself

It can hold a lethal charge. Buy a new one!

If the cable or PSU is not the cause of the problem, then test the RAM memory. First remove and re-seat the memory modules. Make sure that you do that properly. You can then use MemTest86 – http://www.memtest86.com –  to test the memory. Click on the FREE DOWNLOAD link on that page.

The second video provides links on its page to tools to use to service a computer – test the memory and the health status of the hard disk drives and SSDs, etc.

Note that you should still be able to access the PC’s BIOS if only the boot drive fails to boot. BIOS access only requires RAM memory, graphics card and motherboard that are working

Crystal Disk Info is a free tool that tests the health and temperature of hard drives and SSDs.

The processor very rarely fails. Therefore, you should only take it into consideration if every other option fails.

If a dead motherboard is the cause, replace it. If you replace it with a recent motherboard that is new or much more recent than the dead motherboard, depending on how old your PC is, you may have to replace the RAM memory and the processor and maybe the PSU itself to newer compatible components.

Diagnosing a dead motherboard of a desktop PC –


About Eric 275 Articles
I am an experienced PC technician who has been the owner and sole writer of the PC Buyer Beware! website since 2004. I am learning all the time in this very dynamic, ever-changing field.