Cross connecting a powersupply to be always on to supply 12v and 5v?

[cmoses]

I am thinking about using a laptop for a MAME project.  If so I would not have a normal computer power supply to draw the 12v and 5v needed for coindoor and control interface. 

Is there a way to wire a or cross connect a power supply so that it would be on all the time when it was receiving electricity?  I figure there must be a way to cross connect a couple of wires on the plug that normally connects to the mother board.  This way when the power supply received electricity it would be on.  I need 12V and 5V to power coin door, lights, control interface, etc and think it would be easiest to do it this way.

Any thoughts?

[MonMotha]

Connect the PS_ON line to a ground line (indicated by COM on that diagram).  The PS_ON, aka "remote", line is often green.  The ground should be black.  This will force the supply to turn on any time it has power.

[cmoses]

Thanks, sounds easy enough.  Any problems or issues in running the power supply when it is not hooked up to a computer?

[MonMotha]

Many power supplies of this nature require a load on the 5V, 12V, or both 5V and 12V rails for proper operation.  Some need load on 3.3V, but this seems less common.  PC power supplies will in general shut down if they have no load (unlike some, especially older, arcade supplies which can sustain damage).  The required load is generally not overly large.  A couple lamps is usually sufficient.