newbie help/computer wont turn on/where to start?

[pcclueless]

I have a HP pavilion 700 desktop that locked up on me. I turned it off to try and reboot it but it wouldn't turn back on. You could hear the fan come on and the activity light would come on but the power and keyboard lights would turn off after a second. After unplugging it for a couple of minutes and trying to turn it on, the power light now stays on and I can hear the processor start up briefly, but it doesn't seem to get up to normal speed and there is no signal to the keyboard or monitor. The activity light turns off after about 20 seconds as usual. Is this common symptoms for a fried HD or MB. I am familiar with basic hardware principles and operation, but know noting about diagnosis and troubleshooting. Nonetheless, I am mechanically inclined and I was hoping someone could help me to fix it myself. Any insight on where to start would be appreciated.

 

[DigitalMicron]

Ummm do you get any video out of the monitor??? It doesn't sound like an HD or MB problem to me. It sounds like you PSU needs to be replaced. How old is this system???

 

[pcclueless]

The monitor stays in standby mode and says no signal so I guess that would mean no video, right? The PC is a little over 3 y/o. Thanks for your help.

 

[PC eye]

Did you hear the default single beep upon first turning the system on? When a bios chip fails on a board nothing will run unless the cpu went bad on you. This type of problem could be that or a failing supply. A bad hard drive wouldn't stop the initial screens from appearing.

 

[pcclueless]

There is no longer a beep when powering up. Is there a way to test the power supply without buying one and replacing it?

 

[SirKenin]

The motherboard is fine and the HDD is fine, but it sounds like you are having problems with the 5V rail from your PSU.

 

[PC eye]

"problems with the 5V rail"???

I thought that was 12v rails. What sounds like the cpu is probably the fan on the heat sink plus the initial power draw on the supply itself. The heaviest draw on current is generally seen when first starting any system and going through the post tests.

 

[SirKenin]

"problems with the 5V rail"???

I thought that was 12v rails. What sounds like the cpu is probably the fan on the heat sink plus the initial power draw on the supply itself. The heaviest draw on current is generally seen when first starting any system and going through the post tests.

5V powers the mobo and fans. 12V powers the CPU, devices (harddrives, optical drives, etc) etc. As you can tell from the OP, the devices are powering up fine. Come on, this is basic tech stuff.

 

[PC eye]

Around here 12v powers the fans(blue led large). A bad cap will throw a monkey wrench into the works as well as a bad bios chip. Talk to my old board on that one. It had plenty power and still.... put.. put... awww...doa!

 

[Bobo]

5V powers the mobo and fans.

Where the heck do you get this kind of stuff? Fans generally (but not always) run off of 12v lines, and the motherboard uses 12v, 5v, and 3.3v.

Come on, this is basic tech stuff.

Which is exactly why I wonder where you get your information

I can hear the processor start up briefly, but it doesn't seem to get up to normal speed

You cannot hear the processor start up. Are you referring to the fan? Or maybe the hard drive?

 

[pcclueless]

Sorry for the confusion. It is the HD I hear spinning up when I turn the computer on. I also forgot to mention for about the last year, the fan would sometimes get a lot louder than normal (like something was getting caught in it) and would go away after a couple of taps on the top of the case. Would this strengthen everyones suspicion of a bad PSU? Is this a cut and dry plug-and-play replacement, or should a pro do it. Thanks for everyones feedback.

 

[Archangel]

the noise you heared was probably because a bearing of a Fan was/is broke, a few tciks can push it into place again fow a wile.

anyway.. did you true to reset the bios already? ( disconnect the PSU from the mobo, and pop the battey for a few seconds is 1 way to do that, a other way is setting the CMOS jumper onto the other 2 pins than than it's on now (but then you would have to find it first )

 

[SirKenin]

Where the heck do you get this kind of stuff? Fans generally (but not always) run off of 12v lines, and the motherboard uses 12v, 5v, and 3.3v. Which is exactly why I wonder where you get your information

You cannot hear the processor start up. Are you referring to the fan? Or maybe the hard drive?

Oh yeah... Right about the fans.. 12V.. Just double checked.. Sorry, two late at night and I was too hasty in posting.

The motherboard doesn't run off of 12V. It runs off of 5V, as well as the PCI cards. You try to feed 12V to the main part of the board and you'll fry it. The 12V line that runs into the board from the PSU powers the CPU...Well, the mobo takes the power and filters it and then feeds it to the CPU...

The CPU interfaces with the mainboard at 3.3V.

 

[StrangleHold]

The 3.3-5V runs the circuits on the motherboard, so if he is hearing fans run and his harddrive spinning up and nothing else, no boot at all and no beep, it could be a shot 3.3 or 5V rail. But it could be a number of other things as well!

 

[pcclueless]

I reset the BIOS according to Archangel's instructions, but still nothing getting to the monitor or keyboard. Are there any other basic things to check before I go buy a PSU?

 

[SirKenin]

Nope. I'm almost 100% certain that it's the PSU that's the problem.

 

[pcclueless]

Wow.........just installed brand new power supply and to my suprise computer has same exact symptoms. Please someone let me know if there are any other possibilities.

 

[SirKenin]

Really? That sucks. The only thing left is the mobo. *sigh* I was hoping it was something cheap.

 

[PC eye]

Did you hear the default single beep upon first turning the system on? When a bios chip fails on a board nothing will run unless the cpu went bad on you. This type of problem could be that or a failing supply. A bad hard drive wouldn't stop the initial screens from appearing.

The motherboard is fine and the HDD is fine, but it sounds like you are having problems with the 5V rail from your PSU.

put... put.... awww.... doa I've been seeing this on a few new boards lately let alone one that's been in use for a period of time.

 

[Bobo]

The motherboard doesn't run off of 12V. It runs off of 5V, as well as the PCI cards. You try to feed 12V to the main part of the board and you'll fry it. The 12V line that runs into the board from the PSU powers the CPU...Well, the mobo takes the power and filters it and then feeds it to the CPU...

The CPU interfaces with the mainboard at 3.3V.

I am quite aware of this.

put... put.... awww.... doa I've been seeing this on a few new boards lately let alone one that's been in use for a period of time.

Any ideas what exactly causes it?