Question Can motherboard be powered by a jumpered PSU?

[PuzzledToo]

My PC just stopped working in the middle of the day, as per this thread.

Question - ASRock mobo stopped working

The PC was on all day but when I went back to use it, it was dead. It did not respond to power off/on. Nothing. It has a B365M Pro4 mobo with a Samsung M.2 SSD. I checked the Corsair PSU & it works & all voltages are correct. Re-connected the cables & tried to power on by jumping the header...

forums.tomshardware.com

Would it be safe to jump pin #16 of the PSU while it is connected to the mobo? That should power up the PSU, but would that damage the mobo since it would be bypassing the normal system that turns on the PSU?

If the mobo is already dead this should not affect it. But would this affect the CPU and/or RAM?

 

[drea.drechsler]

It may not power-up the PSU, but that alone won't harm the motherboard or CPU. But if the motherboard isn't powering up in the normal manner (using the power pins on front panel header) then something's wrong and it's not ever a good idea to ignore that even if it does power up.

 

[PuzzledToo]

I agree it's not the best idea. I figured if the mobo is bad what's there to lose?

If RAM or CPU or SSD are removed to protect them, will it boot to BIOS and display its information? That would let me note changes I've made so they could be applied to a replacement mobo.

 

[drea.drechsler]

I agree it's not the best idea. I figured if the mobo is bad what's there to lose?

If RAM or CPU or SSD are removed to protect them, will it boot to BIOS and display its information? That would let me note changes I've made so they could be applied to a replacement mobo.

If the operating system SSD is removed it should start directly into BIOS. But if CPU or (all) RAM is missing it will halt in POST and either beep out an error code (to a system speaker) or light trouble shooting LED's to assist.

EDIT add: but that's only IF the PSU thinks it's safe to (try to) start up the system.

 

[Eximo]

Forcing the PSU to start in that way is effectively the same as holding the power button down. Only reason to force a PSU start is to independently check the voltages. If you get 12V, 5V, and 3.3V open circuit, that is some information telling you the PSU is working (only definitive test is a real load, or a simulated load PSU tester).

PSU might appear to be working with say 12V, the fan will spin. But if 5V or 3.3V aren't working, then the system won't boot. A cheap 10-15 dollar multimeter can confirm this for you.

(It seems you did do voltage checking, I am just putting this here for anyone else that comes across it)

Troubleshooting:

Remove/disconnect everything from the motherboard but power, see if the PSU will turn on then (you can still plug in the power button if you don't want to short the pins)

If it doesn't stay on at that point, it is safe to say the motherboard has an internal short somewhere.

If the PSU stays on at that point, try putting in the CPU. See if it stays on. Repeat with the memory, and so on until it either works or doesn't start.

 

[sajid_ali]

Jumping the pin #16 of the PSU to power it up while it is connected to the motherboard is generally not recommended, as it may cause damage to the PSU, the motherboard, the CPU, and/or the RAM.

Pin #16 is the "Power-On" pin and it is used to turn on the PSU by sending a signal from the motherboard. Bypassing this normal system to turn on the PSU directly by jumping the pin could potentially damage the PSU and/or the motherboard. Additionally, it can also cause damage to the CPU and RAM if they are powered up before the voltage regulation circuit of the PSU is properly enabled.

It's important to diagnose the root cause of the problem before attempting to turn on the PSU. It is possible that the problem is with the PSU, but it's also possible that the problem is with the motherboard, the CPU, or the RAM.

A better option would be to disconnect all the components from the motherboard and then try turning on the PSU. If the PSU works fine when it's disconnected, then you can start connecting the components back one by one and see if the problem is with one of them.

If the problem is with the PSU, it's recommended to replace it with a new one. If the problem is with the other components, you can try replacing them or getting them repaired.