Solved No POST beep. CPU fan does not start. Reset button does not work. Is it a PSU problem?

The problem and question:
My PC does not start, and I need to know 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 (sound of hte 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:
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. 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 does not work. 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.
5. I connected a Raspberry Pi to the monitor, and I know the monitor works fine.

Hardware:

• Motherboard: Gigabyte 880 GM Rev 3.1.
• PSU: Frontech 450W.

Thanks. I was considering trying with a new PSU, but before buying one, I was hoping to diagnose the problem given the symptoms. Since the PSU fan works fine and considering that the power switch and reset button of the cabinet is unable to switch off the PC or restart it, I was wondering if it may be a problem with the motherboard. I had even tried removing the CMOS battery and placing it back after a few minutes.

Yes Evan, I bought an NZXT 550W Bronze rated PSU today (it came with a ridiculous 16A power cord which didn't fit into any socket in my room, so after asking at the NZXT franchisee service centre, I used my old 6A power cord for the NZXT PSU) and connected the 24 pin connector and the 8 pin CPU connector to the motherboard and switched on the computer. The same CPU fan twitching problem is happening. The computer does not boot. I think this might either be planned obsolesence by Gigabyte, or perhaps the earlier Frontech PSU messed up the motherboard when resuming from suspend. From the motherboard, there are 4 pins which supply power to the CPU fan. I removed the connector and used a multimeter to check if those pins are receiving power, and they are.
Anyway, if the motherboard is dead and there's no other way to verify that the problem is indeed with the motherboard, I guess I'll just buy a new motherboard, RAM and CPU (though I hope to salvage the old AMD FX 4100 AM3+ processor that's currently installed).

@Bruce: It's very kind of you to ask. I tried with the NZXT's 16A power cord too, but the computer does not start. Probably a planned obsolescence executed by Gigabyte. I remember a BIOS update happened without my permission around a year ago (I remember instances of the computer restarting randomly or not waking up from sleep, but this not waking up used to happen with an Acer E11 laptop too). I've seen such "No POST" issues being reported recently on another forum too. Those were ASUS and MSI boards. I wonder if this is some planned "epidemic" or whether hackers are randomly selecting systems to disable just for the fun of it. What still bugs me is that even though this is a 12 year old self-assembled PC, I have no ability to undo the BIOS update and potentially save the motherboard. My perfectly usable RAM (upgraded 7 months ago) and CPU have now gone for a waste.
If you had asked because you wanted to close the thread, please feel free to do so.

Bruce said:

with the power supply being a) the most likely candidate and b) an easy part to swap out, any chance you can get your hands on one for testing purposes.
a unit from a friend, neighbour, family, or work?

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I mentioned purchasing a new PSU. No use.

I removed the CPU cooler, took out the CPU, removed the 11 year old thermal paste on the CPU and the cooler, connected back everything, 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's like it did an auto shutoff of the power. The processor and cooler fins were extremely hot. I could smell the metal being hot. So if this auto-shutdown worked, does it mean that at least some parts of the motherboard are working?
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 shut down or 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 suspend mode, the phone was draining power from the computer, and probably messed up some capacitor?

Bruce said:

Nav, we are spinning our wheels here, the good money is on the power supply unit being to blame.
until that can be addressed, we are in no-man's land.

Click to expand...

Thanks Bruce. I don't have anyone here who'd lend an SMPS for testing. However, I have an analog multimeter, and I followed the instructions here to test the Frontech SMPS. I'm not an electronics person, but on the 24 pin connector, I was able to get the +3.3V readings (for one wire it was +3.5V), the +12V readings and the -12V reading (blue wire, where I switched the red and black probes of the multimeter. For the red wires, I got a +5.6V reading. It should've been +5.5, but I understand that there can be small variations. Also checked that no voltage was detected for the black wires. Even for the CPU power connector, the yellow wires showed a +12V reading. So since the SMPS fan is spinning and the voltages are correct, I assume the motherboard stopped working as a result of either some voltage fluctuation when I woke the PC from suspend or due to planned obsolescence. A year ago, a BIOS update happened automatically without my permission, and the message showed me where the backup BIOS file was stored. I had copied that file into a pen drive. The Gigabyte 880GM Rev3.1 is supposed to have a dual BIOS (the second BIOS data overwrites the main BIOS if data corruption happens), so I planned to try flash the BIOS with either the backup file or a downloaded BIOS file. However, the motherboard manual says I have to press Esc during POST, to start QFlash. So it looks like I'll just have to give up and buy a new motherboard, RAM and CPU. Am grateful for your help.

I agree with you Rustys. However, in my case, the only load was the AMD FX 4100 CPU and the stock Cooler Master heatsink. I tried with and without my PS2 keyboard and 1 RAM stick of 2GB. Also tried with and without the VGA cable connected. The internal speaker was connected to the motherboard. So at least a beep or at least something should have shown up on the monitor. As a last resort, at the shop where I'm going to purchase the new components, I'll ask if they can spare a PSU to test my motherboard before replacing it with a new one. I'll be buying a new one regardless. If the current motherboard can be revived, it'd serve as a useful backup or as a server.

Rustys said:

You posted this information in another forum and have failed to post this vital information here.

Click to expand...

I had mentioned it here. Do scroll up, and you'll see it. The post I made on Thursday. The lack of thermal paste and the CPU fan not spinning at full speed was the reason that the computer auto-switched off after running for around 20 minutes. But the boot problem was there even before removing the CPU and thermal paste. I had tried using the NZXT SMPS before taking out the CPU and thermal paste. btw, NZXT's official support in Europe replied, saying I can use the old 6A power cord instead of the 16A power cord that NZXT supplied. In case you are wondering, I had also tried with the 16A power cord (there's a socket in the kitchen). I'm very grateful that y'all followed up and tried your best to help. But I think we had better abandon this effort. I'll just buy a new motherboard. A few days ago I raised a support ticket with Gigabyte, where I shared with them the link to this thread. No response yet.

I used the same newly purchased NZXT SMPS with a new MSI B550M board and a Ryzen 5 3600G. The SMPS works. So that means either the Gigabyte motherboard had been fried by the old Frontech SMPS or it developed some fault or it may have been planned obsolescence. I guess it's time to move on with the new motherboard. I would like to thank everyone in this forum for the care that y'all gave. I was surprised when one of you had asked if the problem was solved, when I had already given up. In most forums, people don't care to ask. I am very grateful for what y'all did. Thank you.

ps: Gigabyte support responded eventually. Even they suspected it may be a PSU issue. They also mention they no longer test this model board since it is old.