Question PC wouldn't turn on. No lights, fans etc. Unplugging/Replugging eventually turned it on. Unplugging would repeat the issue, what happened

[donnieberry]

As the title says, the issue has since been resolved as I replaced my motherboard and PSU, but I would like to understand exactly what happened in the first place so I can avoid this situation in the future.

I've cleaned my PC many times and always do it the same way. Open the side panel, use a Compucleaner to blow dust out and use a anti-static brush if needed. I never put one finger on the motherboard directly either. Also, when blowing fans, I put one finger on the fan to stop them from spinning.

I decided to clean my pc out after around 6 months. So, I unplugged it, cleaned it, plugged it back in, pressed the power button, nothing. No lights, no fan spin, nothing.

I done the following:

• Took GPU out
• Did the paperclip test with the PSU
• Jumped the front panel pins
• Triple-checked all connectors
• Took out all USB's
• Reset CMOS
• Replaced CMOS battery
• Had an IT technician test my PSU and it passed all tests
• Technician also inspected the board & case for anything that could cause a short and found nothing
• Drained power from PC by holding the power button for 30 seconds after unplugging

Eventually, after unplugging and plugging back in the power cable many times (think 10 - 20 times), the PC turned on and all was fine, but the CMOS would reset.

From that point, the PC would shut down and turn on just fine if I shut down via the OS and the CMOS would not reset, but the symptoms would come back if I unplugged the power cable, back to the same issue, no power whatsoever. When it eventually turns on after again, unplugging and replugging the power cable, it will shut down and turn on no via the OS problem. And like I said, the CMOS would reset every time this happened.

I ended up replacing my PSU and Motherboard as part of an upgrade and now I can unplug my PC and plug it back in just fine.

But it begs the question, what exactly happened? What broke inside my PC and what caused it?

The best assumption I had was that when I was unplugging the power cable from the PC, all of the power would drain from the motherboard, so that when I pressed the power button, it wouldn't even have enough power to turn on, and eventually after unplugging/replugging the power cable, JUST enough power would enter, allowing me to power the machine on.

 

[Lutfij]

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

I ended up replacing my PSU and Motherboard as part of an upgrade and now I can unplug my PC and plug it back in just fine.
An assumption since you didn't mention the specs to your build, but perhaps your PSU was on it's way out or you have a wiring issue in your abode or the wall outlet at the very least.

The best assumption I had was that when I was unplugging the power cable from the PC, all of the power would drain from the motherboard
That would then lead me to think you have a grounding issue, if you need to discharge the build with physical contact.

Was the CMOS battery exhibiting more than 3v?

Lastly, you should consider reinstalling the OS as you've changed motherboards. It'll save you one(or more)grey hair(s) in the future.

 

[donnieberry]

When posting a thread of troubleshooting nature, it's customary to include your full system's specs. Please list the specs to your build like so:
CPU:
CPU cooler:
Motherboard:
Ram:
SSD/HDD:
GPU:
PSU:
Chassis:
OS:
Monitor:
include the age of the PSU apart from it's make and model. BIOS version for your motherboard at this moment of time.

I ended up replacing my PSU and Motherboard as part of an upgrade and now I can unplug my PC and plug it back in just fine.
An assumption since you didn't mention the specs to your build, but perhaps your PSU was on it's way out or you have a wiring issue in your abode or the wall outlet at the very least.

The best assumption I had was that when I was unplugging the power cable from the PC, all of the power would drain from the motherboard
That would then lead me to think you have a grounding issue, if you need to discharge the build with physical contact.

Was the CMOS battery exhibiting more than 3v?

Lastly, you should consider reinstalling the OS as you've changed motherboards. It'll save you one(or more)grey hair(s) in the future.

CPU: i7 10700k
CPU cooler: Thermalright Peerless Assassin 120 SE
Motherboard: MSI MAG Z490 TOMAHAWK
Ram: 2 x 16gb Sticks
SSD/HDD: 1tb M.2 SSD
GPU: Nvidia RTX 4090
PSU: Corsair RM1000e
Chassis: Fractal Torrent
OS: Windows 11
Monitor: Gigabyte M32U

---

The PSU was around 2 years old at the time of replacement.

Also regarding the CMOS battery, I didn't check the voltage, but as part of my debugging process, I did replace the battery with a fresh one straight from the shop and it had no effect. The CMOS would still reset when I unplugged the PC.