Motherboard light comes on but power button does nothing

thorkle

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Feb 12, 2010
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I just installed a new zalman cooler on my mother baord and degreased and applied some mx-2, and now My computer won't even attempt to turn on, even though the green light on the motherboard is as bright as day. I tried using a different cpu, different ram, I'm alost positive its not the case, it was working earlier today, I suspect that the power supply may have gone bad. The specs are as follows:
Motherboard: Asus p5kpl-cm
Memory: 4gb (2*2gb) OCZ Reaper 1066 mhz ddr2
CPU: Intel e8500
Graphics: 8800gts
Power Supply:LOGISYS Computer PS575XBK 575W ATX12V SLI Ready Power Supply

Can someone please help me out, The jumper settings are fine according to the manual, everything was in working order earlier today before I had to take out the motherboard to apply the back plate. I am highly confused, someone please help.

I am going to try bread boarding in the morning, if this still does not work, I will be at a loss once more, and will probably end up buying a new PSU unless otherwise directed logically
 

jsc

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Goodness. I get to use the same reply two times in a row.

Our standard checklist and troubleshooting thread:
http://www.tomshardware.com/forum/261145-31-read-posting-boot-problems

The motherboard LED is tied to the small, always on, 10 - 15 watts, standby power supply. It has nothing to do with the functioning of the main power circuits that run the computer. About all it means is the the PC is plugged into the wall and the PSU switch is on.

Try to borrow a known good PSU. Or better yet, see if you can test your PSU in another working system. If you cannot do that, try to borrow a DMM to measure the voltages. Yellow wires should be 12 volts. Red wires: +5 volts, orange wires: +3.3 volts, blue wire : -12 volts, violet wire: 5 volts always on. The gray wire is really important. It should go from 0 to +5 volts when you turn the PSU on with the case switch. CPU needs this signal to boot.

You can turn on the PSU by completely disconnecting the PSU and using a paperclip or jumper wire to short the green wire to one of the neighboring black wires.

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead.

If it passes this, reconnect and repeat by connecting the DMM to back of the main power plug.

Logisys is not known for being high quality.

Breadboarding is a good way to isolate case problems from the rest of the system. I think I have the earliest breadboard thread on the forums. If you haven't seen it:
http://www.tomshardware.com/forum/262730-31-breadboarding
 

thorkle

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Feb 12, 2010
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Thanks for the help guys, Like I said, everything is plugged in correctly. Their are only two possibilities that could be causing failure to turn on after reading the check list (thank you very much Jsc). Either I have the board mounted incorrectly in the case, or I have a dead power supply. I am quite thankful for this, since neither are expensive problems to fix. I think I am going to get a new power supply no matter what because I bought this current PSU just over two years ago, when I used to go almost completely for budget parts rather than reliability. Plus I could use the extra PSU to build my self a little Frankenstein computer
 

thorkle

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Feb 12, 2010
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Thank you once again guys. It turns out the power supply was just fine (just like you thought jtt283). I had the mobo installed poorly. I'm gonna stop being lazy with my installation from now on, and use mobo stands and such.
 

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