Pavilion Elite M9040N turns itself on and off continuous

[johngibbons]

I have a Pavilion Elite M9040N media centre desktop and it started turning itself on and off continuously.  The fans, the DVD drive and the power button light all turn on for about 3-4 seconds then it turns off for about 3-4 seconds then starts the cycle again.  The bios doesn't get to start and nothing comes up on the monitor.  I changed the power supply hoping that was the problem but no luck.

Has anyone run into this before?

Does anyone know what is going on?

Thanks

John

[Big_Dave]

Try the below procedure and see if you can isolate the issue. Don't skip any steps.

Trouble Shooting Power Supply Issues.

[johngibbons]

Update

When the power supply is plugged in the green light is on and without pressing the power button the computer starts itself on (fans and DVD drive start spinning, light around the power button illuminates.  After about 3-4s the computer shuts itself off again (green light on power supply goes out, fans and DVD drive stop spinning, light around power button goes out).  After about 3-4 s the whole process starts again.

I tried to follow the steps outlined on the HP support page for green light on resolving power supply issues for Windows 7, but I can't get to the bios page before it shuts down and starts the cycle again.

I left the new power supply in the computer and plugged the old power supply in, the green light turned on and stayed on, so the original power supply is not the problem.

I tried the steps in the "green light on or flashing" to the point where it indicated a bad component.  Following the instructions to the point where it said the issue is likely to be a bad component so I removed the 2 PCI cards (tuner and video card), and the memory neither resolved the issue. 

From the possible bad components list that leaves motherboard or processor.  The thing that gets me is that the computer turns itself on and off with out the power switch being touched.  Does mean it is more likely to be the motherboard then the processor?

John

[Big_Dave]

You might want to check the switch.  Trace the switch wire to the motherboard and then unplug the wire. Now plug the PC in. Does it power up?

Try clearing the CMOS.  It's a long shot.

[johngibbons]

Update 2

I traced the power switch wires back to the mother board and unplugged it.  Turned on the computer and still no change from the cycle on on and off.

Following the instructions for clearing the CMOS, When I plugged the computer back in it did not start the cycle of on and off immediately.  So I pushed the power button and the on and off cycle started again.

I found a replacement mother board on ebay at a reasonable price since it is not longer available through HP.  It is apparently new and an exact replacement from ASUS so hopefully that will work.  I thought about an after market mother board but decide I would rather get my system back up and running then start from scratch rebuilding it.

I will update after I get the mother board and have a chance to install it.

Thanks for your help!

John

[johngibbons]

Update 3

I managed to get a replacement motherboard on Ebay from China.  It was an exact replacement even had the correct HP part number on it.

I replaced the motherboard and the issue with it turning on and off has been resolved.  

I now have a new issue.  After the bios boots it get the following dos message 

BOOTMGR is missing

Pres Ctrl+Alt+Del to reboot

I suspected I may have inadvertently switched the sata data cable locations on the motherboard for the two hard drives.  I switched their positions and was able to boot the computer.  Windows went into start up repair, I suspected to see something like this given the replacement of the motherboard.

It is trying to repair itself know, I will let you know if I am able to resolve this issue or if I have to reinstall Windows.

John 

[Big_Dave]

John,

Good show!

[johngibbons]

Update

Not good news,  The Windows self repair rebooted the computer after it was done and it never came back up.  It beeps from the moment it is turned on.  Two short beeps then one long beep.  It repeats this cycle several times then goes into a long series of short beeps.

Anyone got any ideas about what is wrong now?

John

[Big_Dave]

John,

This might help.  HP BIOS beep codes.

[johngibbons]

Update

The beep codes indicate video problems.  I pulled and reseated the video card, no change.  I pulled the card out completely and the computer stopped beeping and appeared to start up.  I can't tell for sure as I can't see anything without a videocard.  

Looks like I am going shopping for a new video card tomorrow.

John