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Maybe I'm missing something really obvious here, but after going through 3 new motherboards in trying to build my new machine, I'm finally certain that the 450W power supply I bought has been destroying them. It seems like it should be simple: just connect the connectors where they fit and switch the thing on. But today after hooking it to my ASUS Sabertooth 990FX TUF Series Motherboard and switching it on, I could see and smell the smoke coming out of the motherboard.

What I don't get is why I can hook this same 450W power supply up to my mATX motherboard and not run into the same problem. What am I missing here? Where on the box or manual is this?

(I have 8x2 GB RAM, AMD FX-4100 3.6GHz CPU, 1 512MB ATI graphics card, 1 WD 7200 RPM SATA hard drive. )

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Do the two motherboards use the exact same power connections? Doesn't the ATX mobo require an 8-pin CPU-power cable versus only 4-pin cable for the microATX mobo? Also, where are these mobos installed; are they in cases or on a workbench? –  sawdust Aug 11 '12 at 17:58
    
They both use same power connections and are in open cases. –  mobile computing Aug 12 '12 at 4:00
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Given that you use the same PSU connections, I'd say that the likelihood that the PSU is the problem is very, very low; there are other areas to suspect first. As a general rule, the likely causes are probably: (1) a short due to metal object on mobo (I've seen this), (2) a short caused by the case, (3) motherboard fault (but with 3 failures seems less likely), (4) faulty adapter card, (5) everything else incl PSU. Given the facts so far I'd put money on #2, the case is causing a short. If you get another mobo, power it up on an insulated surface (e.g. the cardboard box in came in). –  sawdust Aug 14 '12 at 7:15
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BTW as a rule you are better off assembling the motherboard outside the case, on a firm surface. Otherwise be careful when pressing down to install components and connectors, and try to avoid flexing the motherboard. –  sawdust Aug 14 '12 at 7:27

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