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Power loss to everything but case fans


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#1
RiffRaffCat75

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OK, got a machine that was working fine and then all of a sudden power died to everything but the case fans. When I got the machine to reboot, it wouldnít stay on for more than 1 to 3 minutes, and then the cycle started all over again with power loss to everything but the case fans. I tried again and got it to stay on long enough to do a backup, so Iím good there, thankfully. Since this looked like a power supply issue, thatís where I started. I replaced the power supply with a known good unit and the machine still did the same thing. The last time it did this I noticed that the south bridge on the motherboard was really hot, like almost too hot to the touch, and it had only been on for about 2 minutes before it shut its self off again. OK, Iím thinking its MOBO failure and it needs to be replaced. Anybody else got any other ideas on this one?

This is a custom built machine and specs are as follows;
-Windows 7 Professional
-Sentey Halcon Black ATX Mid Tower
-ASUS Sabertooth 990FX
-AMD FX-8120 Zambezi 3.1GHz 8Core Processor
-CORSAIR Vengeance 16GB
-SAPPHIRE Radeon HD 6570 2GB
-Seagate Barracuda 500GB
-COOLER MASTER GX Series 750W Power Supply
-Logitech X-530 70 watts RMS 5.1 Speaker System
-LG Black BD-ROM Super Multi Blue
-LG 22X Super-Multi DVD Burner
-LG Flatron 22' LCD monitor
-Logitech Black Wireless combo

Side note; this same machine has done this before in the past like twice and at those times I didn't think much of it because everything continued to work fine there after, until 2 days ago.
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#2
phillpower2

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Hi RiffRaffCat75

You may have a short circuit somewhere so I suggest that you do a bare-bones set-up outside of the case, see details below, if this was a thermal issue the whole system would shut down to protect the CPU from frying.

A short circuit can occur in the MB itself, be caused by a bare wire or if the MB is not properly grounded on the case including the I/O plate at the rear of the case.

Bare-bones set-up details;

First remove the MB and do a barebones set-up on a piece of cardboard (make sure it is larger than the MB) only connect the PSU, the GFX card, 1 stick of Ram and the keyboard.
IF your MB doesn`t have a power test switch you will then need to short out the 2 power on pins on the MB header to get the PSU to activate, you can use a small flat bladed screwdriver or a paper clip bent into a U shape, this is perfectly safe if you do not touch anything else, the idea is to see if we can get a BIOS screen if you do you can then add one component at a time until you find the problem component, you must power down and remove the power cord from the wall before adding a component,

Other things worth checking include, if you used stand offs beneath the MB are they securely tightened otherwise the MB will short out, check for stray screws or bared wires for the same reason, check the case switches (power and reset) and finally remove the CMOS battery for a few moments and then replace it - just in case you have a bad BIOS setting, see attachment below;
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#3
RiffRaffCat75

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Alright, it turned out to be a bad mobo and was replaced by ASUS. Then this morning, for the first time ever, I get a Voltage warning pop up from ASUS AI monitor. So I open the monitor and the voltage on the Vcore is all over the place. I'm not sure what it should be, but it goes up and down from 0.888 to 1.367 to 1.080 to 1.368 to 0.888 to 1.212 to 0.970 and all over again. Now it is a constant flow of power but it is fluctuating a lot between these numbers. I have replaced the power supply with a new one and it is still doing it. Is this normal or ok, and if not, what could it be? The MOBO?
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#4
phillpower2

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When you next boot up go into the BIOS and select the MBs default settings, if no joy please refer to the information in my reply #2 regarding clearing the CMOS in case of a bad BIOS - MB setting.

Post back with the results please.
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#5
RiffRaffCat75

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Alright, I tried that and no change. Also, it had it's first BSOD, crash, and reboot, so now what? I'm thinking the mobo is going to have to be replaced again. I'm getting to the point of just buying a new mobo and just be done with it. I just wish I had $200 bucks to do so right now. I guess it will just be down another month again. And no, I didn't get a look at the blue screen before it rebooted. It was only up for a few seconds.

Edited by RiffRaffCat75, 25 August 2012 - 08:20 PM.

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#6
phillpower2

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Was the bare-bones set up that I suggested in my reply #2 ever done if yes what was the result please, if no it may be necessary to do it if after checking the Ram as suggested below if there is no change.

How to physically test your Ram.

The following checks require the computer case to be opened so take the following
safety precautions 1st, disconnect the power cord from the wall socket and take anti static
precautions before touching anything inside, you can do this by touching a bare metal
part of the case.


Have a pencil and notepad to hand.
Remove each stick of Ram and blow out the memory slots.
Insert the first stick of Ram in memory slot one, reconnect the power and in the case of a desktop computer the video to screen cable.
Power up the computer and see how it goes.
Make a note of the results.
Repeat the procedure until the first stick of Ram has been tested in each memory slot and the results written down.
Remove the first stick of Ram and put it to one side on top of a piece of paper with the number one on it for identification purposes.
Repeat the procedure with all Ram until each stick has been tested in all slots, the results written down and the sticks identified numerically.
Please note that some MBs (motherboards) will not boot unless there is Ram in slot one so please refer to your user manual.

Can you also temporarily disable the auto re-start so that if it blue screens while you are doing the testing you will be able to write down the stop code details for us "how to" below;

Just before the Windows 7 splash screen shown above appears, or just before your PC automatically restarts, press the F8 key to enter Advanced Boot Options.

You should now see the Advanced Boot Options screen as shown in the attached .jpeg below.

Using the arrow keys on your keyboard, highlight Disable automatic restart on system failure and press Enter.

After disabling the automatic restart on system failure option, Windows 7 may or may not continue to load depending on what kind of Blue Screen of Death or other major system problem Windows 7 is having.

Post here any stop codes that you may receive please.

A list of Stop Codes provided courtesy of cheathawk1 http://www.geekstogo...ath-stop-codes/
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