A few weeks ago I tried to turn on my computer, and nothing happened. After checking all the connections and trying different things, I found out that I needed to push in the power button and hold it in for at least 5 seconds or so before the computer would power up. Normally, the computer would power up instantaneously as soon as I pushed in the power button.

Since this first occurred a few weeks ago, it now takes over 10 seconds of pushing the power button and holding it in before the computer powers up. So whatever the problem is, it seems to be getting worse.

The computer is a Dell 4550 and is nearly 5 years old. In the past I would often turn the computer on and off manually every day via the power button, but lately I've been leaving the machine powered up 24/7.

My computer runs perfectly fine once it does boot up. It's just the pushing in of the power button that's the problem. Any suggestions on how I should address this?

Sounds like the transformer in the power supply is going out.

A transformer should either work of fail, nothing in between. There could be a component on the board inside the PSU that is failing, or there could be a problem with the motherboard as there is a relation between the momentary switch closing which shorts the green wire in the PSU bundle via the motherboard to turn on the PSU.

agreed, Try unplugging the main power harness from the motherboard and grounding the green wire (pin16) on the connector to the black wire ( pin 15 or 17 ) next to it, if the power supply comes on immediately its not the power supply. If you have access to a voltmeter with continuity test you can check the power switch function and make sure its operating properly. This Link describes the function of the power switch and how it should operate (and how the old ones used to).

First things first! Either unplug the computer or turn off the PSU by the switch on the rear before you try this. Forget counting the pins and they differ on the 20 and 24 pin connector, there's only one green wire and you can use any black wire, place a jumper between the green wire socket and any black wire socket. If your PSU has a switch on the rear of the case that is the best way to turn it back on, but plugging it back in works as well.

The on/off switch on the front of the case is a momentary type that when pushed makes contact between the two wires from the header and only maintains contact as long as the switch is depressed.

Thanks for the responses! Before I did anything, a friend told me to first just try using a can of compressed air to blow out any dust inside the machine. After doing this, the response time after pressing in the power button has improved considerably! So too much dust might have been the whole problem. At least, I'm hoping it was something that simple. I'll keep an eye on things in the days ahead and see if the problem returns.

switch could have been dusty