Help diagnosing a nonworking HP

[forsailbyowner]

I'm looking at a HP pavillion a350n of my girlfriends. Apparently she took it to a local computer shop that is no longer there and paid $150 to get it fixed. When I plug it in it lights up,fan starts up, whirring sound starts then it shuts off. No beeps. What next? Do I follow the steps, take mobo, psu , video card and 1 memory stick and try a startup outside the case? there's no spare money in her household. She's mother of 15yr old quints and is a teacher. There's no computer at her house now and with school these days its kind of a must to have one. Thanks

[David M]

Is there someone with a computer they are not using that they would like to donate?

[forsailbyowner]

I pulled the power supply out and am not showing voltage testing with multimeter on red and black leads and the fan doesn't start in the power supply. Am I testing the right wires? I saw on craigslist someone giving away computer parts. Maybe see what I can come up with. I live on a sailboat and have been doing a refit for the last 3 months. When I work on my boat I'm not working on other peoples(how I make ends meet) so I'm scraping the bottom of the barrel right now. The kids had been using my laptop till it slid off a lap hit the floor and the. hard drive went kaput.

[glc]

When you try to test an ATX power supply that's not connected to a motherboard, you have to "jump" the green wire to a black wire to get it to start.

How To Manually Test a Power Supply With a Multimeter

[forsailbyowner]

Originally Posted by glc When you try to test an ATX power supply that's not connected to a motherboard, you have to "jump" the green wire to a black wire to get it to start. How To Manually Test a Power Supply With a Multimeter

Ok that worked. I had all the proper voltages.

[forsailbyowner]

Got mobo out, on cardboard, 1 stick memory and video card installed and hooked to monitor. Fan starts as soon as power is put to power supply. Not supposed to without jumping power switch terminals? Hey its doing more than it did in case. In my deluded mind I think I'm getting somewhere lol.

[forsailbyowner]

Was dead on water. Fan spun but no display, then swapped out to a different memory stick and Viola!! Got display!! I'm thinking the switch is bad too. When you push it in it stays in and clicks when its pulled out. If it stuck would that cause the computer to start then shut off?

[rjfvillarosa]

Originally Posted by forsailbyowner If it stuck would that cause the computer to start then shut off?

Very likely yes. That switch is a momentary switch, meaning it only makes contact for the moment it is pressed, the idea being that it completes a circuit sending a signal to the PSU/Motherboard to start up. If the switch stuck on it would probably cause the machine to do a start/stop loop, not good.

[forsailbyowner]

Well I hooked up the hard drive and windows loads. What has got me a little confused is the computer boots as soon as I plug it in without jumping the terminals. This is still outside the case without power on switch hooked up. Another thing I noticed is the fan on the heat sink starts up spinning fast then slows down quite noticeably sometime during the boot process. Is this normal?

[rjfvillarosa]

Originally Posted by forsailbyowner What has got me a little confused is the computer boots as soon as I plug it in without jumping the terminals.

Almost everytime I have seen this it has been caused by a faulty PSU. If that switch has been sticking on it is very likely that it has damaged the "switching" inside the PSU hence your problem.

[David M]

That's normal. The default speed of the fan is 100%. When the fan controller software boots the speed drops so it is quieter.

Disconnect the power on switch on the case and see if it still boots when you power on the PSU. If it doesn't then put a screwdriver across the power on terminals on the motherboard and see if it boots. If it does then that indicates your power on switch has shorted.

[rjfvillarosa]

Dave. He still has it in an "out of case" state on the table.

[David M]

I know. I had the impression he had the power on button wires leading outside the case to the mobo. I have had some that are long enough to reach.

[forsailbyowner]

I got mobo back in case. When I plug it in it boots, but I'm able to shut it down from windows then start it again by jumping the terminals. The switch in the case is shot. It just stays in when you push it and has to be pulled out. Currently I'm to a point where I seem to be fine with just the floppy and HDD hooked up. As soon as I hook anything else up it freezes at the HP screen. Then when I unhook the hardware that froze it, reboot, and freezes at same screen. If I unhook the HDD, pull the battery out, start it until it says no bootable drive, then start again it boots to windows. I need to find the keyboard. So far just working with a mouse. I'm hoping there's something I can access in the bios that will see me thru the freeze ups

[rjfvillarosa]

I have a feeling that "sticky switch" has blown the motherboard.