Mobo powers on without switch

Help. New build. Connect PSU to mobo and turn on PSU power. Mobo fires without post or boot. Case fans, cpu fan and vid card fans all spin. Case switch does nothing (doesn't even need to be connected). Reset either. True on bench test or in the box. Cant find anything online. Anyone seen this. Im afraid something is shorted in mobo. Thought CPU and memory, but cant see how this would allow power up. mobo is biostar t5 xe cfx-sli lga; i5-760, and antec 750 watt psu.

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  1. Have you got a spare PSU you could try? My first guess is that an always-on PSU is busted.

    Or try this - plug in the PSU without connecting it to anything. If it turns on, you've identified the problem.
  2. Yes, i've used two seperate PSUs ... same issue with both.

    Haven't tried the PSU alone idea ... will try at lunch. thx.

    Did speak with manufacturer tech rep ... advised clear CMOS (did that already before they suggested - nothing changed) and then remove/reinstall/replace mobo bat ... (haven't tried that - but not sure how that might help) ...

    Finally, they suggest RMA :(
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