ATX Power Supply powering Jamma or vice-versa.

[Numbski]

So I'm wondering if there's any extensive documentation out there on this topic.  I'm 90% certain that an arcade power supply has all of the lines required to power an ATX mainboard, and an ATX Power Supply has the lines needed to power a Jamma-compliant arcade board.

I'm trying to save some space inside the bottom of my cabinet.  I know that an ATX board has some sort of power sensing that I can't just hack it up and turn it on.  I know wattage might be a concern, but let's presume I have a nice solid 600 or 700 watt power supply - something that could easily power both a PC and a Jamma Board simultaneously without issue.

Are there any solid guides on this topic?  If I can have just one power supply inside the cab instead of 2, it would go a long way for me.  I'm torn as to which one I would want to keep.  I guess it would be nice to throw the switch for the arcade PSU and just bring that up with the monitor, and if I want to run Mame, perhaps toss a second switch to bring up the PC.

[grantspain]

you can bypass the power switch on an atx easily
one thing that an atx will not give you an adjustable +5 v ,not strictly that important but older boards do need +5 at the correct level

if you had a standard switch mode in then you will not have the outputs required to run a pc

[Numbski]

Could you clarify what you mean?  "Standard switch mode, then you would not have proper inputs to power a pc".

[grantspain]

a standard jamma switch mode supply will have the following outputs
+5
+12
ground
-5   or +24

you pc mobo needs -12v,3.3v

[Numbski]

Ah, I see.  So really if I'm going with one power supply, it needs to be an ATX.  Not a problem.  Just need to figure out how to bypass the auto-sensing on so that I can control which device gets powered on and when.

So far as the concern about +5V, couldn't I just wire a potentiometer in-line between the 5V line of the power supply and the Jamma harness?

[grantspain]

to bypass power on then short pin 14(green) to ground(black)
http://pinouts.ru/Power/atxpower_pinout.shtml

remember you will not have a facility to adjust the +5v

[Numbski]

remember you will not have a facility to adjust the +5v

The more I think about what you're saying, the more I think it's not hard to fix.  Do a small circuit to step up the voltage to 6V, then put a pot on it to adjust it down beneath that.  Then you should be able to control the +5V to your liking without much trouble.

[grantspain]

well i guess you could do the same if you removed one of the resistors on the +5 v output and replaced it with a pot inside the psu