Computer wont start, no post, no noise

[DarkKnight]

I'm having trouble with an HP 750n computer. The computer wont start at all. When I hit the power button, no lights turn on, i dont hear any noise, and nothing comes on the screen. I opened it up and noticed that when I first plug the power in, and hit he power button, the cpu and system fan spin for 3 seconds, and then stops. If I press power again, nothing happens. It looks like the motherboard is getting power because the green light on it is on when the power is plugged in.

My sister took the computer on a trip and she said that it worked before she left the place. She said that there were no power outages over there so I dont think that the board got fried. She says that maybe it got bumped aronnd a little bit in the car, but when i opened it up everthing looked intact. I also dusted out the computer, but still same results.

Is there anything else i should do to make the computer work again?

 

[mechBgon]

Here's one idea to check into:

You know how if you press the power button, the system should start, and if you keep it pressed, it takes that as a shut-down-or-else command and turns off. So if your power switch were stuck in the pressed position internally, then when the computer was plugged in, the mobo would go "oh! the button's been pressed, gotta power up!" and then it would see "dang! the button's being held, gotta power down!"

To test that theory, you might start by removing the bezel and just taking a good look at the electrical switch, and if you have a continuity tester, you could test whether the switch is acting as if it's always being pressed.

Or... you could simply pull the case's wiring plug off of the motherboard, and now plug the system in and see if it does not power itself up, now that it's not hooked up to the case's switch.

Does that make sense?

 

[DarkKnight]

I found out that the computers powersupply is broken by testing another psu with the computer, so i guess it needs a new psu. The problem is that the size doesnt seem standard. The hp powersupply is 5.9" wide, 3.4" tall, and 4" deep. Does anyone know a place where i can get a psu this size?