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Throughout the day, my Windows 7 desktop system is shutting down without warning every 2-6 hours or so. The frequency seems to be getting greater, but I'm not yet completely sure of that fact. This is the third day that this has been recurring. I replaced the motherboard (to: Asus Sabertooth 990FX) and CPU (to: AMD 8 core) about 1 month ago due to a fried chip on the previously 4 year old motherboard. The PSU is a 4 year old Corsair HX750w. During the past 4 years, I've never had a hardware issue other than the fried motherboard. I'm running a low power single slot graphics card, due to no onboard video, and don't currently play games. I don't think that too much power consumption is an issue absent the possibility of a PSU issue.

My CPU temp hovers at a steady average of about 42C. The mainboard is at 35C, the fans are running without issue, and the voltages are as follows: +3.3v = 3.147V; +5V = 4.974V; +12V = 12.055V. I have low latency (cas 7), low voltage G.Skill RAM installed that is not on the Motherboard approved list (carried over from my last setup). However, the motherboard seemed to instantly adjust and just runs the 8 Gb of RAM at different timings and voltages (1.5v vs 1.3v) than the RAM has the optimum potential for. It hasn't been a problem thusfar, and in actuality the updated hardware gives me better RAM performance (operations per second) than did the previous equipment according to the windows experience index.

It doesn't automatically reboot after it shuts down, and it doesn't restart when I press the power button. It does restart after I tilt the case slightly and then press the power button. Every time this happens, I need to tilt the case slightly and then it starts right back up. Today, for the first time, it restarted after I merely titled the case slightly without pressing the power button.

This seems to be a strange set of symptoms, and I thank anyone ahead of time who may have any insight into this.

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Anything in the event logs? Is it possible there is a short or something like that in the case? –  Mitch Jul 21 at 17:41
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What you describe is everything I would expect when a PSU is starting to fail. –  Ramhound Jul 21 at 17:53

2 Answers 2

I would check your case, the fact that it will turn on and off by tilting the case to me screams that there might be an issue with the power switch. Unless you've changed the case in the last 4 years, it could be just general wear and tear, if you have spare case I would try moving things into that, or buy a cheap replacement to experiment with.

Edit: or a short in the case, when you changed the motherboard did you ensure that nothing was touching anything it shouldn't be?

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My prime suspect here would be the PSU.

I'm thinking there's something that's a bit loose and is moving due to heat. When you tip the case it falls back into place and the machine works again.

While I see Sam's point I disagree--because the power switch is only a temporary contact anyway. If it fails open nothing happens.

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