Build a PC Power button doesn't work with new PSU

I am fixing a PC for a friend; their power supply went bad, so i switched it but now the PC will NOT turn on using the front PC button but rather it turns on when i plug in the cable in the Power Supply.

& Furthermore, it shows nothing on the monitor when it turns on...

The Power Supply Fan is working, CD Drive open normally & i can hear the Hard drive moving...

Can you guys give me a bit of advance on what i should do next please?


Posts: 1,703   +171
Are you sure you plugged all the connectors correctly? The PC not switching on from the front button would seem to indicate the power switch is not plugged into the motherboard.


Posts: 1,020   +56
Hi, With the monitor not showing an image, does it show anything at all?
Such as 'no input signal' message? Check right through from the mains lead, then to which socket you are attaching the monitor to on the motherboard.
Also is the monitor power by it's own mains lead, or does it take power from the pc's psu ? (Used to be common but not so much today.)
Is the pc using a separate graphics card? Or is it using the integrated graphics option? You wouldn't be the first to plug the monitor into the wrong output socket.
Regarding the power on button, look for a twisted pair of wires leading out from the front panel, on mine they are blue and black but that can be different of course.
You should find a black plug on the end marked 'Pwrsw'
On the multi-pin header on the motherboard, look for the pins marked 'pwrbttn', and connect the twisted pair 'Pwrsw' plug to that point.


Posts: 471   +4
Is the PC OEM or custom built? If OEM what brand and model? Did you make sure to plug in the 4pin CPU connector? Could be power button although it turning on as soon as you plug the power cord in could also indicate a motherboard problem. If the power button is disconnected it shouldn't turn on at all. PSUs (especially cheap ones) love to take motherboards with them when they go so there is the possibility that the old PSU damaged the motherboard. Also what brand and model PSU did you use to replace the bad one? A poor quality PSU or one with insufficient wattage can also cause problems like this.
I had this problem before.

First tell us what is the brand and model number of the client's pc. Also what was the brand and model number of the psu that you used as a replacement.

I had this problem with a client before. In my case the PSU failed and it rendered the motherboard unusable.

In regards to, "the PC will NOT turn on using the front PC button but rather it turns on when i plug in the cable in the Power Supply". I believe that you should check that all of the psu connectors are properly plugged in to the motherboard. Also make sure that the power button connectors are properly connected to the motherboard.

In regards to, "it shows nothing on the monitor when it turns on." At first this may display symptoms of a dead GPU. Does the client have a dedicated graphic card? If so then make sure you connected the video cable to the graphic card instead of the integrated graphics. However, if the client just has an integrated graphics. Then it may be the culprit. When the PSU died, it could have destroyed components on the motherboard. So in my situation, a replacement video card did not work.

This is what you could do.
1. Get a replacement motherboard. (Be careful if you are using an oem case because oem cases may only accept non standard motherboard sizes, and make sure the fan and cpu are compatible with the motherboard.) In situations like this you need to make sure that majority of the components on the system are functional

2. I never had this work in this situation, but if you install a secondary graphic card then you could get the video work. However, when you are dealing with a motherboard that was damaged by a psu then that might not work. If this was a case where the integrated graphics just died by itself then that solution would be plausible.