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No boot, fans running, and no Beeps

Last response: in Systems
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April 26, 2010 4:32:00 AM

I turn on my computer (home built and working for 4 years) and get no boot. The fans run but the monitors (power button) flashes as if there is nothing to display (different than if there was no signal, seems like a sleep mode).

I took the memory out and got a long repeating beep, so I think the mobo is still working.

What could it be? I tired switching video cards so that is not the problem.

Any tips?
April 26, 2010 5:42:19 AM

Well the PC has been working fine, it is not a new build. I'll run through the list when I have time.

But the lack of beeps once the RAM is back in makes my think the PSU has gone bad. Just seems odd the fans and everything would come on if the PSU was bad.
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a b B Homebuilt system
April 26, 2010 1:54:59 PM

It would help us a lot if you would post your COMPLETE system specs so we know what we're working with. A PSU that can muster enough power to run a system fan may or may not be able to provide enough power to run a system. A cheap PSU can cause all sorts of problems, but this sounds like something else to me.

Have you tried booting with each stick of RAM installed by itself? That's step #6 on the checklist. The checklist isn't just for new builds. It's a general troubleshooting guide for all systems.
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a c 122 B Homebuilt system
April 26, 2010 2:52:19 PM

Or you could have all the voltages, but there's something wrong with the "Power Good" signal from the PSU to the motherboard. If that's not right, even with all the power voltages present, your PC will not boot.

Work the checklist. Then, if the PC still not working, the best way to test the PSU is by substituting a known good one of similar capacity. Brand new, out of the box, untested is not a known good one.

Breadboard - that will isolate any kind of case problem.
http://www.tomshardware.com/forum/262730-31-breadboardi...
Breadboard with just motherboard, CPU & HSF, case speaker, and PSU.

You can turn on the PC by momentarily shorting the two pins that the case power switch goes to.

You should hear a series of long, single beeps indicating memory problems.
Silence indicates a problem with (in most likely order) the PSU, motherboard, or CPU.

Next best thing is to get (or borrow) a digital multimeter and check the PSU.
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.
http://www.youtube.com/watch?v=5FWXgQSokF4&feature=yout...

This checks the PSU under no load conditions, so it is not completely reliable. But if it can not pass this, it is dead. Then repeat the checks with the PSU plugged into the computer to put a load on the PSU. You can carefully probe the pins from the back of the main power connector.
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April 26, 2010 4:06:01 PM

Dang, looks like I have my work cut out for me :o  . Really temped just to buy a new PSU and give it a go. Perhaps that is just hope :??: 

At least there are beeps when I take the memory out, gives me hope that the mobo is still good.
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April 27, 2010 2:54:59 AM

UPDATE:

I went through the wrong checklist expect the bread boarding. It seems I can get a long repeating beep out of the mobo speaker if I remove all the RAM. I have 1 sticks of 1GB each and I have tried them all as singles and in different slots.

Computer turns on, fans on, I hear spinning up, but nothing. Monitor power buttons just flash as if it was sleeping, as opposed to no signal when i put the cord.

PSU?
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