System works outside of case, inside it starts for a second then stops

[Glenn Joseph]

My system http:// works fine when i breadboarded it outside of the case but inside of the case, it turns on for half a second, the fans, led's although it doesn't show anything on the monitor, i've tried everything suggested that i've seen, i've flipped the psu, loosened mobo screws and changed the ram to every slot and nothing is working, please help and advise

 

[GhislainG]

If exactly the same connectors are used, then something has to be shorting out when the motherboard is in the case (extra post or backplate). Why would you flip the PSU for that type of issue?

 

[Paperdoc]

As GhislainG says, something is shorting when you mount things in your case. By far the most common cause of this is misplaced stand-offs.

Stand-offs are short metal tube-like things with a threaded hole in one end, and a threaded short shaft coming out the other. In most cases they MUST be used to mount the mobo in the case so they provide enough clearance to keep the mobo bottom metal traces away from the case itself. These little parts come with your case. The important thing is to place them correctly.

A mobo typically has about 9 holes through it around the board used for fastening it to the case via the stand-offs. Each of these usually has a pattern (often like a star) of little metal fingers radiating out from it a short distance. These are where you put screws through into stand-offs mounted in the case underneath. These are designed to ensure that the mobo is grounded to the case at these specific points, but NOWHERE ELSE.

Now a case is designed often for several mobo "standard" layouts and thus has many places for installing the stand-offs it comes with. Very often some already are mounted in threaded case holes. What you have to do BEFORE installing the mobo is examine where the mobo holes really are, and then arrange for stand-offs to be screwed into the case exactly where those mobo holes are. Ideally there should be a stand-off to accept a screw under very mobo mounting hole, but sometimes one or two don't match up. But THIS is really IMPORTANT: there should NEVER be a stand-off under the mobo where there is NO hole! Having a stand-off at the wrong place can short out the metal traces on the mobo there. Also, having NO stand-offs usually means that the mobo bottom is shorting out to the case in several places.

So, carefully review the placement of stand-offs and the mounting holes in your mobo, and make them match up.