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HP Desktop won't power on.

Last response: in Motherboards
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June 16, 2011 3:58:47 AM

After using some compressed air to clean out some dust from my HP Pavillion a6242n, my computer no longer powers on.
The green light on the power supply is on but when I press the power button, nothing happens except the green light goes off (even with only the mobo connected and all other devices disconnected).
I've used a multimeter to check the PSU and the Power button and they are fine.
I checked the motherboard and saw no signs of damage, but could it be that my mobo is dead now? How can I know for sure? And could there be something I'm missing?

Thanks in advance.

My computer:
HP Pavillion a6242n
Mobo: MCP61PM-HM (Nettle2)
CPU: AMD Athlon 64 X2 4800+
RAM: 3GB DDR2(2x1GB+2x512MB)
Graphics: MSI Nvidia GeForce 210
PSU: HP-D2537F3R 250W

More about : desktop power

a b V Motherboard
a b α HP
June 16, 2011 4:15:54 AM

have tried to take out the video card and memory, and then turn it on?

is the CPU fan working? unplug it and plug it back in.
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June 16, 2011 4:24:06 AM

yes I have, to no avail. Just to be clear, no fan or anything turns on when I press the power button now. The only thing I notice is that the power supply green light turns off and stays off until I unplug the power and re-plug the machine back in.
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June 16, 2011 8:46:19 PM

I have noticed something interesting, I tried disconnecting the 4 pin ATX connector and pressed the power button, and I think the fans and drives start up, but nothing boots up. This leads me to think that it could be a CPU-Mobo error. (when I reconnect the 4 pin ATX cable nothing goes.

Any ideas?
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a b V Motherboard
a b α HP
June 16, 2011 9:12:51 PM

bad CPU fan speed sensor wire
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June 18, 2011 1:06:04 AM

what exactly is the CPU fan speed sensor wire?
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a b V Motherboard
a b α HP
June 18, 2011 1:23:10 AM

one of the tree or four wires, usually the yellow one, connecting to the MOBO lets the BIOS know if the fan is spinning and at what speed.

if the BIOS does not detect the right signal from the fan, it will not boot to protect the CPU.

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June 18, 2011 7:44:42 PM

Checked the fan, doesn't seem to have anything wrong with it because with or without the CPU only when I unplug the ATX12V 4-pin cable do the fans turn on. Otherwise, nothing boots.
I think it has to do with the 4-pin connector on the motherboard, but I have no way of testing if that is true.
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a b V Motherboard
a b α HP
June 18, 2011 8:32:26 PM

do you have another PSU you could use for testing?

the 4PIN ATX is the power for the CPU
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June 18, 2011 11:41:04 PM

I don't have a spare one with a 4-pin connector, but I did already use a multimeter to check the voltages of each lead, and they were all fine.
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November 10, 2012 6:52:55 PM

Sadly, the same story happened to my HP Pavilion desktop, too. I googled and found your posting one year back. Just check if you eventually found and fixed the problem? Thanks.

Jyh-shiarn
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November 10, 2012 8:02:41 PM

I ended up concluding that the motherboard just got fried. Gutted my machine for its parts. Sorry I can't be of more help.
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!