[SOLVED] No POST beep. CPU fan does not start. Reset button does not work. Is it a PSU or motherboard problem?

[Nav9]

I've been through the "No POST", "system won't boot" checklist on this forum, but my case is different. Here, the PC was working fine until I put it on suspend (which I've done plenty of times before too) and tried resuming it.

The problem and question:
My PC does not start, and I need to know from the symptoms below, if it is a problem with the PSU or the motherboard, to decide which to replace.

How the problem began:
Everything was working fine. I used Ubuntu 20's "Suspend" option to put the PC in suspend mode. When I tried resuming from suspend, the PSU fan appeared to start (I can see and hear the PSU fan running), nothing showed up on the monitor, the reset button didn't restart the PC and pressing the power button for a few seconds didn't shutdown the PC either.

What I've tried:

1. Opened the cabinet and noticed the CPU fan is not starting (it twitches every few seconds, like as though it is going to start, but does not). This video shows it happening:
   View: https://youtu.be/m_NQ63D-lnw
   .
2. Tried removing all RAM modules and disconnected the keyboard and mouse and started the PC. Hoped to hear a beep error, but there was no beep.
3. The PSU fan and another fan are working fine. I tried spinning the CPU fan with my finger, and it spins lazily on its own when given this initial nudge. But if I switch off the power and press the PC power button to start the PC, the CPU fan does not start on its own.
4. As mentioned earlier, pressing the reset button does not restart the PC. When everything was working fine, if I switched on the power supply switch and pressed any key on my keyboard, the PC would start. Now this feature no longer works. I have to switch on the power supply switch and then press the power button on the PC cabinet to start the PC. I can't use the power button on the PC to switch off the PC. Only switching of the main power supply switch can switch off the PC now. When things were working fine, I could press and hold the power button on the PC to make it switch off.
5. I connected a Raspberry Pi to the monitor, and I know the monitor works fine.
6. Removed the CMOS battery, waited 5 minutes and placed the battery back.

Hardware:

• Motherboard: Gigabyte 880 GM Rev 3.1.
• PSU: Frontech 450W, AC 230V.

Asked the question here initially, but I was hoping someone on Tom's Hardware would recognize the symptoms.
Note: I have a vague memory of this kind of problem happening earlier too, but I think it resolved on its own once I switched off the computer and switched it back on. I wonder if it's a problem with dust or summer heat?

 

[Lutfij]

Welcome to the forums, newcomer!

PSU: Frontech 450W, AC 230V.
Try and work with another PSU, one that's reliably built, borrowed from a friend or neighbor.

 

[Nav9]

Welcome to the forums, newcomer!

PSU: Frontech 450W, AC 230V.
Try and work with another PSU, one that's reliably built, borrowed from a friend or neighbor.

Thank you for the welcome. So it seems like the PSU is the problem. I took it out of the cabinet, removed the dust and now it wont start. Checked the power input with a multimeter, and the problem is not with the power cable.
Dont know anyone nearby who'd lend a PSU temporarily, so I'll prolly have to buy a new good quality 650W or 600W PSU so that I'll be able to re-use it when I buy a new motherboard (the Gigabyte 880GM is quite old). Else, I could take it to a local repair shop and ask them to try with a spare PSU.
Thanks for the help.

 

[DSzymborski]

Thank you for the welcome. So it seems like the PSU is the problem. I took it out of the cabinet, removed the dust and now it wont start. Dont know anyone here who'd lend a PSU temporarily, so I'll prolly have to buy a new good quality 650W or 600W PSU so that I'll be able to re-use it when I buy a new motherboard (the Gigabyte 880GM is quite old). Else, I could take it to a local repair shop and ask them to try with a spare PSU.
Thanks for the help.

It's possible the PSU is the problem. Are you shorting the correct pins to start a PSU without a motherboard? It won't start otherwise.

Something else could be the problem; one of the many, many problems of junk-tier PSUs is that as soon as you have any kind of problem that could be power-related, you need to replace it to eliminate it from the equation. So it makes sense to just get something that isn't dodgy the first time.

 

[Nav9]

PC does not start even now. I bought an NZXT 550W Bronze rated SMPS (ASUS was unavailable). The manufacturer was ridiculous enough to give a 16A plug with it. I asked the service centre, and they said it's ok to use my old SMPS's 6A power cord with the NZXT. So I used the 6A power cord, connected the 24 pin ATX connector and the 8 pin CPU connector to the motherboard and switched on the PC. The same CPU fan twitching problem is happening.
So is it safe to assume that the problem is with the motherboard and the problem is not because I used the 6A power cord?
Planned obsolecence, I assume, since it is 10 years since I bought the Gigabyte 880GM. Rev 3.1. Now I need to figure out which motherboard will be appropriate for the NZXT when it runs with a 6A power cord.

 

[Nav9]

Removed the CPU cooler and CPU. Removed the 11 year old thermal paste. Connected back everything (without adding any new thermal paste), used the old Frontech SMPS, but this time I used only 1 stick of RAM. Pressed the power button, and I see that the problem continues. The CPU fan does not start, but twitches every 4 seconds. So I spun the CPU fan with my finger, and then it continued spinning on its own lazily. I let the system run like this. After around 20 minutes,the PSU fans and all other fans stopped working. It felt like a familiar power off. It's like it did an auto shutdown. The processor and cooler fins were extremely hot. I could smell the metal being hot. So if this auto-shutdown due to processor overheating worked, it means that at least some instructions of the motherboard are working. A signal went from the motherboard to the SMPS, to make it stop.
One thing I missed mentioning, was that before the whole problem began, I was using the computer normally and had connected my phone to the USB port of the computer. When going for dinner, I put the computer in suspend mode (Ubuntu). On returning, the computer wouldn't restart or wake from suspend. At this point, my phone was at 86% charge. I disconnected my phone from the PC and went to sleep. In the morning, the phone's charge was at 13%. Some app had consumed a lot of power. I wonder if during the PC's suspend mode, the phone was draining power from the computer, and probably messed up some capacitor?

 

[Nav9]

Update: The NZXT SMPS works fine. I used it with a new motherboard and CPU. So the problem does indeed seem to be with the old Gigabyte motherboard. Either the old Frontech SMPS fried the motherboard or it may have been planned obsolescence. Moving on with the new motherboard now. Thanks to everyone who offered help.