PC Building

[Homi]

Hey guys I got a upgrade to am5 recently but while testing the powersupply did not turn on when connected to the motherboard but it works when connected to a powersupply tester. My motherboard is a msi pro a620m and my cpu is 7600x.

[elstaci]

Generally you can turn on your PSU manually to enable output power by shorting out two pins (Green and Black wire pins) on the Motherboard's cable as shown:

Connect a case fan to one of the PSU cables if it starts running normally then your PSU is good and the problem is with your motherboard or a connected hardware.

If you have a hard short on your motherboard that would prevent the PSU  from working since it would shut off immediately to prevent damage or a damaged 24 pin motherboard connection.

A short can be something like a motherboard screw shorting out to the computer case or some other obstacles shorting out the Motherboard.

If you remove the Motherboard from the PC Case and the PSU works indicates a screw is shorting out the PSU when the motherboard was installed or some other metallic short after removing all connections from the motherboard first.

First visually check the Motherboard's 24 pin connector and make sure it isn't physically damaged. Then I would disconnect all hardware from your Motherboard including the CPU including all Case fans and all cables.

Just leave one Case Fan connected to troubleshoot.

When you connect the PSU does any Motherboard LED light up or Case fans start working?  Does the PSU look like it is shut off?

If not it would indicate a defective Motherboard. I would then remove the Motherboard and reconnect the PSU to see if it works and to physically check the Motherboard for damage or burn marks.

EDIT: @FunkZ brought up an excellent tip that I forgot. IF the Case Power Switch is bad that would also prevent the PSU from turning on. So I would following FunkZ advice first to rule out the PC Power on switch.

[Homi]

My power supply worked for my first pc but when I connect the 24 pin to the motherboard then it doesn't turn on but the motherboard is new 

[FunkZ · Accepted solution]

If the power supply powers on when connected to a tester (which completes the turn-on circuit that @elstaci details) then the problem is with the motherboard or power-on switch header.

Verify that the case power switch is good and is closing the circuit on the power-on header. Alternately you can simply jumper across the two header pins to close the circuit with a flat bladed screwdriver for example.

[Homi]

I think it's the motherboard then

[BigAl01]

Did you resolve the problem @Homi ?  

[Homi]

Yes and no. I found the solution but didn't buy the motherboard yet. The problem was with the motherboard because it either came doa or I made it die.

[BigAl01]

In general, I build systems outside of the case.  I verify the components are working and then I install the motherboard, PSU, etc.

In fact, I once had a shorting situation with a motherboard that was mounted in the case.  I believe it was a screw that had fallen underneath the motherboard.  Yes, I had to replace the motherboard.

The case switch not being connected properly, or the switch could be bad, is a good idea to check.  It's a momentary contact type switch.