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Bad power supply?

Last response: in Components
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October 15, 2010 12:32:18 AM

I recently rebuilt my computer and I'm having a problem with shutting it down and restarting. When I try to restart it it seems to go fine but then goes to a blank screen and just hangs there. I then have to hold the power button until I hear the fans turn off.

When I try to shut down the computer seems to turn off but the fans keep running and I have to hold the power button till the fans turn off. Then press it again to turn the computer back on. Today I tried to update the bios and it wouldn't boot up after trying to load the defaults. I tried to boot it up 2 or 3 times then I noticed the lights on my keyboard and mouse didn't turn off. I then using the power switch on the power supply and everything finally turned off and I was able to boot up again.

Are these normal symptoms of a bad power supply? The power supply is a brand new cosair tx750. I'm going to have my cousin bring over a spare power supply he has and see if that solves the problem tomorrow.

More about : bad power supply

a b ) Power supply
October 15, 2010 1:35:34 AM

This could be a bad power supply problem and the substitution of the power supply is the best test. However the symptoms you describe could also be due to an overclocked processor. After upgrading your BIOS you should clear the CMOS memory by REMOVING THE MAINS LEAD and then moving temporarily the clear CMOS link.
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October 15, 2010 9:25:22 AM

Thats a good idea, try your friends PSU. Because this issue might or might not be because of your PSU, some times this can happen because of bad or faulty Mobo too.
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a c 121 ) Power supply
October 15, 2010 4:42:38 PM

Simple solutions first. Try pjmelect's suggestion to reset your BIOS to defaults. Turn the PSU switch off (or unplug it), move the CLRCMOS jumper, wait a minute or so, move it back, plug in and/or turn on the PSU, and test.
If it still doesn't work, remove all but one RAM stick and see if it will boot. If it doesn't, try a different single stick. If it does, test all your RAM.
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October 15, 2010 11:41:00 PM

Okay I tried the other power supply same problems. So I reset the bios and reloaded defaults and it restarts fine now, but I still have the same problems shutting it down. The fans stay on after I shutdown and I have to hold the power button to turn them off. This happens with 2 sticks of ram or with 1 stick (tried both sticks).

I also ran memtest last week 3 times on a diff computer and it passed. I ram it once with both sticks in and twice with each other stick. Is it normal for the fans to keep spinning after shutdown?
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a b ) Power supply
October 16, 2010 12:25:35 AM

You didn’t say what operating system you are using, but if it is Vista or Windows 7 the power off button can be programmed to perform several functions such as sleep, hibernate or shut down. By Default the power button in Vista is set to put the computer into Vista sleep mode.

http://www.arsgeek.com/2007/05/18/how-to-make-your-vist...
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October 16, 2010 1:01:33 AM

Well I'm using windows 7 and when I was shutting down I would right click on the power icon and go to shut down. I also checked to make sure the power buttons default was set to shutdown in the power options.
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a c 121 ) Power supply
October 16, 2010 1:11:31 AM

Which fans are continuing to run? Some PSUs run their fans for a minute or so after they are turned off, to provide additional cooling.
I don't know if any mobos continue to run fans [at low speed] for a while using +5VSB, but I suppose it's possible...
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October 16, 2010 1:21:43 AM

The fans that continue to run are my cpu fan and my 2 case fans. They all are running at full speed. Not sure if the fans on my video cards are still running though. It's always been way longer then a min.
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a c 121 ) Power supply
October 16, 2010 1:37:21 AM

Odd. I don't think I've ever seen that happen before. Since you've switched PSUs, I'm inclined to think it must be the motherboard. Contact your motherboard manufacturer's tech support and see what they say, or, since you just got it, RMA the board anyway.
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October 16, 2010 3:26:59 PM

Okay guys I think I've narrowed it down a little more. I just set my computer up outside the case on cardboard to see if anything was shorting it. It seemed to shutdown and restart fine, but when I put in my 2nd video card it gave me the same shutdown problem. I'm using an asus m4n75td with a gtx 460 and a gt20 for my third monitor mainly. When I put in the gt 240 it wont' shutdown anymore all the fans keep running the video card fans, cpu and probably the case fans if they were in.

My question is there something wrong with the motherboard?
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a b ) Power supply
October 17, 2010 1:21:09 AM

I think we are back to where we started. Not shutting down with the extra graphics card could be caused by an under powered power supply or a faulty motherboard. Silly idea, try disconnecting the CD drive(s) does it now shut down with the extra graphics card fitted?
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October 17, 2010 1:40:13 AM

I didn't hook up the dvd drive and i'm using my cosair 750watt psu. Shouldn't that be enough power?
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a c 121 ) Power supply
October 17, 2010 2:18:32 AM

If you use just the GT240, what happens? What if you use just your GTX460, but put in the other slot?
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a b ) Power supply
October 17, 2010 7:17:28 AM

Thinking about your problem a bit more I don’t think that the power supply is bad nor do I think that the motherboard is faulty as such. Are you sure that you have connected all of the power leads to the graphics cards and connected all power leads to the motherboard? I would very carefully check this if I were you. If all power leads are connected as they should be then I conclude that you have a design fault with your motherboard and that replacing it with another one of identical type will not cure the problem. It may be a good idea to contact the maker of your motherboard technical support to see if they have any suggestions and to see if this is a known problem.
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October 17, 2010 9:00:24 AM

This is quite rare indeed - When you press the power button in the front panel it will send signal to the motherboard to switched the PSU off if the circuit responsible for this defective - instead turning it off it send signal to your PSU to turn it ON. Return the motherboard.
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October 17, 2010 10:09:26 AM

Yeah I'm sure all the power connections are in the correct places. The computer shutdown fine with just the gt 240, and it shutsdown fine when I have the gt 240 in the pci express slot 1 and the gtx 460 in the 2nd slot. Does it matter what slot my gtx 460 is in?

I'd rather just figure out if something is wrong with the mobo now if possible because I do plan on sling the 460 in a couple of months and it would be a bummer to have to rma the motherboard after buying another video card.
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October 17, 2010 9:17:25 PM

Okay today I put an old 8600 gt I had into the 2nd slot and it shuts down fine but the gt 240 won't so i'm confused. I'm pretty sure the 8600gt draws more power then the gt 240.
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