I received a recent in person computer repair customer. They brought me an HP Pavilion slimline S3507C computer that would not power on. After closer inspection the power button would not engage power.
I tried the proverbial release of any electro static discharge. You want to make sure that the power cable is disconnected from both the back of the computer and wall outlet. Now press and hold the power button for at least 30 seconds.
This did not fix this no power problem. I took the case cover off. You will need to remove three screws on the rear of the computer that tightens down the cover. Now you can remove the case cover.
Also, I had to remove two screws to loosen the multi card reader. The card reader is right next to the power button. The power button on this HP Pavilion Slimline S3507 is a two to three inch wider button.
This power button is attached to the front cover. You can release the front cover by pinching four plastic release mechanisms. Once I was able to get the front cover off, I found the small plastic power button.
With modern computers, many times power buttons are simply one plastic button that presses down on another smaller switch that is often times made out of plastic as well. You want to become careful with the smaller switch because the cables can snap off. Also, the smaller plastic piece that you press down on can break.
I plugged the power cable back into the computer and wall outlet. However, pressing directly on the smaller power switch did NOT engage power. I gently moved the power switch around and kept tapping it. Finally, when I pressed down on the switch, power successfully engaged.
Also, you could try disconnecting the power lead to the motherboard, if you still cannot get the power to engage. I placed the front cover on and booted the computer into Microsoft Windows. I tested using the larger power button on the front cover a handful of times until I was satisfied that I successfully fixed this no power issue.
My computer repair experiences with power switches, are that they rarely fail. However, you could replace the smaller switch that attaches to the motherboard if you still cannot get it to engage power. Many times I notice that the smaller switch that connects directly to the motherboard sticks and does not engage properly.
I notice more power switches that were broken than actually fail.