Question Abnormal behaviour of sleep, shutdown and powered-off states on my PC ?

[syjxsk]

I've been observing weird behavior in the last 2 months of my 4yo self-built Ryzen PC.

I've uploaded 2 Videos on YouTube showcasing the problem,

When powering ON the PSU (Scenario-1)

When shutting down the PC (Scenario-2)

In Scenario-1, at 0:08 seconds of the video, as I turn on the switch, the hdd/system activity LED & EZ Debug LED (showing CPU fault) on my MoBo turns ON and remains ON until I press the power button on the cabinet to turn ON the system itself.

In Scenario-2, as I shutdown the PC, at 0:06 seconds of the video, power button light turns OFF as intended but hdd/system activity LED turns ON and remains ON along with all the System fans running at a constant speed until power switch for the PSU is toggled OFF.

Is my PSU at fault? Or is the Motherboard? I've a gut feeling that my PSU is showing these signs of failure. Please help me troubleshoot this issue, PC runs fine as it is, but my usage has been sparse since I've also got a gaming laptop with me.

PC Specs
MBD: MSI B550 Tomahawk
CPU: AMD Ryzen 5 3600
GPU: Nvidia GT 710
RAM: Crucial Ballistix 32GB (16GB x 2) 3600MHz CL16
PSU: Gigabyte B700H 700W

 

[Ralston18]

Refer to the Motherboards User Guide/Manual and double check the case/front panel connections.

It is very easy to get the connections mixed up.

This Motherboard?

https://download.msi.com/archive/mnu_exe/mb/MPGB550GAMINGPLUS_EN.pdf

Verify that I found the appliable User Manual.

Front Panel connections are presented on physically numbered Page 33.

 

[syjxsk]

Refer to the Motherboards User Guide/Manual and double check the case/front panel connections.

It is very easy to get the connections mixed up.

This Motherboard?

https://download.msi.com/archive/mnu_exe/mb/MPGB550GAMINGPLUS_EN.pdf

Verify that I found the appliable User Manual.

Front Panel connections are presented on physically numbered Page 33.

This motherboard -> https://download.msi.com/archive/mnu_exe/mb/MAGB550TOMAHAWK.pdf

I've double checked the connections of my case's front panel IO and switches with Motherboard and they're all okay.

I haven't touched them at all since 2020, this issue started happening recently. I redid the power ON and OFF test got the same result

 

[syjxsk]

Removed all peripherals except system fans, same behavior was observed
Video link below
PSU turned ON with all peripherals removed

 

[Ralston18]

Install a fresh CMOS battery per the User Guide/Manual instructions for doing so.

Do you have a multimeter and know how to use it? Or know someone who does?

FYI:

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158

PSU is not under load: however, any voltages out of spec would make the PSU very suspect.

 

[syjxsk]

Install a fresh CMOS battery per the User Guide/Manual instructions for doing so.

Do you have a multimeter and know how to use it? Or know someone who does?

FYI:

https://www.lifewire.com/how-to-manually-test-a-power-supply-with-a-multimeter-2626158

PSU is not under load: however, any voltages out of spec would make the PSU very suspect.

Bought a new CMOS battery and installed it, got the same result.

As for multimeter, Yes I do know how to use it, will have to borrow one of those from my workplace tomorrow.

Will report you later with the values

 

[syjxsk]

@Ralston18 I think we've caught something here very strange with this PSU haha

Voltages measured below with GND probe at Pin 24 when PSU wasn't powered ON,

Pin 1	0V
Pin 2	0V
Pin 4	0V
Pin 6	0V
Pin 9	5V
Pin 10	0V
Pin 11	0V
Pin 12	0V
Pin 13	0V
Pin 14	0V
Pin 21	0V
Pin 22	0V
Pin 23	0V

Voltages measured below with GND probe at Pin 24 when PSU was powered ON,

Pin 1	3.39V
Pin 2	3.39V
Pin 4	5.05V
Pin 6	5.06V
Pin 9	5.05V
Pin 10	12.03V
Pin 11	12.03V
Pin 12	3.39V
Pin 13	3.39V
Pin 14	-11.53V
Pin 21	5.06V
Pin 22	5.06V
Pin 23	5.06V

What I found really interesting were the observations listed down with voltages measured as I turn on the PSU's toggle switch at the back, but didn't power ON the PSU

+ve probe	-ve probe	Volts
Pin 2	Pin 18	3.38V
Pin 1	Pin 17	3.34V decreasing down to 1.7V gradually
Pin 13	Pin 18	3.34V
Pin 4	Pin 18	2.75V decreasing down to 1.7V gradually
Pin 11	Pin 18	14.34V decreasing down to 0.1V gradually

This isn't supposed to happen according to Section 4.1.3.1 of ATX Spec as per my understanding.
Video recorded during measurement
Looking forward to your opinion, hopefully my formatting of texts and table here are clear so that anyone easily understand.

 

[Ralston18]

I do not remember seeing the voltages decrease as you observed.

Not sure about what is happening with those gradual discharges but you may be seeing some capacitor discharging....

That said, lets' double check the process:

Did you disconnect all connectors? Red wire in video is at Pin 24 (COM) - correct?

Noted that 5 volts on Pin 9 - standby ( SB) voltage per the Lifewire link.

And you are using/referencing the voltage specs provided on physically numbered Page 20 of the ATX spec - correct?

Measure via the connectors as shown in the Lifewire link. I could not see a jumper wire - Pins 15 and 16 (Step 5) in the video.

 

[syjxsk]

Did you disconnect all connectors?

Yes.

Red wire in video is at Pin 24 (COM) - correct?

No, that was the Pin 1 (+3.3v).
Red wire is positive probe of my multimeter and while recording the video I was measuring Pin 1 (+3.3v) with respect to Pin 17 (COM)

And you are using/referencing the voltage specs provided on physically numbered Page 20 of the ATX spec - correct?

Correct

Measure via the connectors as shown in the Lifewire link. I could not see a jumper wire - Pins 15 and 16 (Step 5) in the video.

Values with jumper wire connected are listed on the 2nd table of my post above (where Pin 14 is reading -11.53 volts)

My video was meant to show the issue that when I don't connect the jumper wire between Pins 15 and 16, I am effectively not providing PS_ON (Power Supply On) command -correct?

Now, as soon as I turn on the PSU's switch, there's some voltage being measured on Pins as listed on 3rd table , which wasn't supposed to happen in my opinion as my PSU wasn't in the ON state. I hope I was clear 😅