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System won't power up after working for 4 months

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February 20, 2007 7:30:21 PM

I put together my first-from-component system last November. Except for a problem with the memory sticks I initially bought, it's been running fine since then--it is not overclocked at all --yet. Yesterday, I tried to power it up and it was dead-dead. No fans case or CPU cooling unit fans came and def. no components. I disconnected the DVD unit, printer and subbed the direct connect keyboard/mouse for the wireless USB units I was used. Ttried swapping each of the 2 memory sticks into one slot only , but nothing. NO BEEPS, no bootup at all--there is just the green power light on the MOtheboard. Should I assume that the power supply is kaput? or could it be something else? I doublechecked all fittings fro/to power supply:

Asus P5B-E motherboard with INtel core 2 duo 6300 and stock cooler
2 Kingston DDR2 667 memory sticks
2 Seagate SATA 300 GB drives
Sunbeam NuuO 550W PSU
SAmsung DVD Burner
Running Windows XP Pro

It's been running real cool and can't think what might have screwed up.

Got it at Newegg so I should be able to return a defective unit.
February 20, 2007 7:36:23 PM

Have you tried reseating the CPU, cleaned, and fresh paste applied. Also clear all dust out of the PC. :) 
February 20, 2007 7:36:51 PM

This is where spare parts really comes in handy.. try plugging in a different power supply just to the motherboard and see if it will at least POST.
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February 20, 2007 7:37:10 PM

Have you tried reseating the CPU, cleaned, and fresh paste applied. Also clear all dust out of the PC. :) 
February 21, 2007 1:02:25 AM

Thanks for the tips... yes, I've tried removing what little dust is there with a pressurized air can and I reseated the cpu fan and reseated it. No difference. Tonight I reset the CMOS jumpter--nada.
February 21, 2007 2:17:48 AM

If it's not the power supply then your Motherboard is dead. This can happen and the green light on the board will still be on. I've replace about 4 Socket 478 mobos's and CPU combos in the last 4 months.(Almost impossible to get Socket 478 Mobos in Aussie, so we replace them with Socket 775 boards and CPU combo) 8)
February 21, 2007 7:35:49 PM

Thanks all.

If I had a spare with enough kick, I'd try that. So I guess I'll RMA it.

I have a surge protector on it, so I don't think it got fried that way.

Sure hope it ain't the MB, but we'll see.
February 21, 2007 9:43:14 PM

You should be able to get a handy little PC power supply tester from Radio Shack or mailorder for around $10.
February 24, 2007 7:31:58 PM

Well, I bought a Power Supply tester and it shows no problems, AFAIK. Except for the -5v lamp not showing --and the tester says that's common--none of the power connections showed any problem. Granted, this was a display type tester--actual voltages don't show---but should I assume
now that it's probably the MOtherboard?

One thing that was curious when I plugged the main 24-pin power and the Molex connector that controlled the case's fans into the tester, the case's cooling fans turned on where previously they hadn't.

If anyone reads this, would you bet that it's the motherboard rather than the power supply?
February 24, 2007 7:33:26 PM

Is it possible that it's just the case's front side power-on switch that's the problem and not the power supply nor the Motherboard? how can I rule out the switch as the issue?
February 24, 2007 8:14:02 PM

Have you checked the case button. These do go from time to time and are overlooked.
February 24, 2007 8:19:13 PM

that was meant to be my question in the previous inquiry--how do I test that the case button/switch is the issue and not something else?
February 24, 2007 8:21:55 PM

Quote:
... the Molex connector that controlled the case's fans into the tester, the case's cooling fans turned on where previously they hadn't.

Not sure quite what you're doing here. How could the case's cooling fans turn on without any power supply connections (you unplugged all the PS connections to test the PS, right?)?
February 24, 2007 8:24:14 PM

Quote:
...how do I test that the case button/switch is the issue and not something else?

Just unplug the front-panel switch's connector from the motherboard header, and use a piece of conductive metal (such as a screwdriver blade) to momentarily short the two header pins together (that's all the main on switch does).
February 24, 2007 8:27:09 PM

I unplugged everything from the system components. I plugged the 20+4 MB power plug into the power supply tester--everything came up green. I plugged the molex power connector that the system fans are also plugged into and they came on--left the 24 pin motherboard power plugged into the tester else I can't tell what's happening with the power to this or any other of the power connectors, like SATA. The CPU cooler did not come on since it's plugged into a separate power source.

What's wrong with this?
February 24, 2007 8:57:10 PM

I still don't understand, sorry.
Quote:
I unplugged everything from the system components. ...the molex power connector that the system fans are also plugged into ...?

If the system fans are plugged into a power connector, how is "everything unplugged from the system components"?
February 24, 2007 9:55:27 PM

On the back of your computer on the power supply there is a switch that is usually black with an O and a | on it. O stands for off and | stands for on. Switch it to on and try pressing the power button again. :lol: 
February 24, 2007 10:00:10 PM

Sometimes a PC's CMOS gets so corrupted that the PC wont react to the power switch, and the CLR cmos jumper wont work.

Before anyone says I am wrong, or jumps up and down complaining that I am suggesting 'Voodoo'....

My partners PC would do this if it ever 'lost power' due to power cut. If you turned it off it was fine, but if you pulled the power plug, then it wouldnt power back up.

However, there's an easy fix thats certainly worth trying.

1) Remove ATX & ATX+12 power connectors from motherboard (wait for mb lights to go out)
2) Remove the CMOS Battery
3) Set Cmos jumper to CLR
4) Wait 5 minutes.. Sometimes just a few seconds is ok, but 5 mins is 99% likely to work
5) Return jumper to standard position, put battery back in, Reconnect the motherboard power cables, and turn on.

If that doesnt work, then its fried. But following that procedure has 'resurrected' many PC's in my experience. Every time I've used it, I had already tried and failed a 'simple' cmos clear.
February 25, 2007 4:09:41 PM

thznks for everyone's suggestions--Iam still dead in the water though for a brief moment today, the system powered up to the system bios before hanging and returning to its old ways.

Yes, the case external power switch is turned on. I may not be an EE but I know that much.

I tried jumping the system power pins both on the motherboard power pins and the ASUS front panel combination Q-Connector.

I changed the case's power fans (not the CPU's) to the onboard fans from the connection to the molex power cable provided by the Power
Supply vendor. The fans didn't come on either connected to the motherboard or to the separate molex cable.

I reseated all power and data connections.

I removed the battery, reset the CMOS/CTR jumper, removed and reseated to its default , reseated the battery and tried again. No go, though based on the suggestion, I'll try it one more time waiting for longer than 20-30 seconds before I reseat everything.

If that doesn't work, my best guess is that the motherboard is the issue, not the power supply. Would that be the next best course of action--replacing the MB?
!