Is it possible it is a PSU problem if ...

[CCCustom]

... the PC shut down abruptly, then although the RGB lighting of the motherboard, the standby LEDs of the motherboard and graphics card are also on, the PC won’t boot up again.

Switched off the PSU and took off the power cord, reset CMOS ... then switch the PSU on again, hit the casing power button and the CPU’s HSF starts to spin again, but before the casing speaker (I fitted 1 of those on, still used to beeps ) beeps the HSF will stop spinning again, leaving the RGB lighting and standby LEDs on.

I have a brand new spare PSU (also Seasonic X750 ) in the store room, so I took the 1 from this setup out and fitted the cables on the spare, and it boots up fine.

Does this mean the old PSU is dying? It’s not brand new, it was from another build previously although that build was hardly ever used.

If it matters ...
CPU : Ryzen 7 2700
Motherboard : ASUS Strix X470F Gaming
PSU : Seasonic X750

 

[pikoman]

... the PC shut down abruptly, then although the RGB lighting of the motherboard, the standby LEDs of the motherboard and graphics card are also on, the PC won’t boot up again.

Switched off the PSU and took off the power cord, reset CMOS ... then switch the PSU on again, hit the casing power button and the CPU’s HSF starts to spin again, but before the casing speaker (I fitted 1 of those on, still used to beeps ) beeps the HSF will stop spinning again, leaving the RGB lighting and standby LEDs on.

I have a brand new spare PSU (also Seasonic X750 ) in the store room, so I took the 1 from this setup out and fitted the cables on the spare, and it boots up fine.

Does this mean the old PSU is dying? It’s not brand new, it was from another build previously although that build was hardly ever used.

If it matters ...
CPU : Ryzen 7 2700
Motherboard : ASUS Strix X470F Gaming
PSU : Seasonic X750

You kinda answered the question yourself. No matter the brand or reputation, non-failure isn't 100%, if its still under warranty just RMA it. You just suay lor

 

[jtjt00]

Your old PSU has degraded to the point the 12v rail is not output sufficient current to power on. You mentioned unit was recycled from previous desktop. How long been used in that setup?

 

[CCCustom]

Your old PSU has degraded to the point the 12v rail is not output sufficient current to power on. You mentioned unit was recycled from previous desktop. How long been used in that setup?

It’s not very old actually, it was a brand new RMA replacement when it was fitted in the other build, only used like once a week for an hour or less, and for less than a year, because it was a computer I put at my mother’s place so I only go there when I bring the kids to visit. My previous PSU failures were more ... obvious? Where they are flat-out failures, not even able to power on the board (and card) lighting.

You kinda answered the question yourself. No matter the brand or reputation, non-failure isn't 100%, if its still under warranty just RMA it. You just suay lor

It’s an RMA replacement itself, and unfortunately following the original unit’s warranty period, this 1 has expired The brand new spare that was in the storeroom, is also an RMA replacement. Seems my personal experience with Seasonics hasn’t been good

 

[jtjt00]

Seasonic X series has issues ............
I have one unit of X 650w at work having noisy fan. Replaced with SuperFlower.