Powering a PCB without its original power supply

[JoyMonkey]

Just to try out something different than putting together Mame cabs, I picked up a Tekken2 vB PCB on eBay. I haven't even thought about a Jamma harness in years, so it'll take me some time to figure out how to get it hooked up right.

Right after the auction I had a thought:
I don't have any arcade power supplies lying around any more. How am I going to power it?
If it just needs 5v and 12v, could I use a PC power supply?


( By the way, while I was looking into buying the PCB, I found a huge archive of Namco PCB manuals in PDF format HERE )

[grafixmonkey]

if it wants 5v and 12v, then the PC power supply should work fine.  (might want to check with someone who's tried it, but I can't think of any reason it wouldn't.)  The PC power supply will be able to provide all the power it needs, at least.

You might need an AT power supply, those have a switch to turn it on and off.  I think the ATX power supplies make it difficult to turn the power on and off without having a motherboard attached to them.  (soft power and all that.)

[OSCAR]

Sure, you can do this.  In fact, I'm doing it here: http://www.arcadecontrols.org/yabbse/index.php?board=10;action=display;threadid=11924

The jamma standard calls for +5, +12, and -5V, all of which are available on a pc power supply.  The drawback is that pc power supplies don't have an adjustable +5V which you may need for some games if you have too much voltage drop due to the game board load or if the wire harness has dirty/corroded pins.  The plus side is that pc power supplies typically are higher amperage than arcade power supplies, and I've heard that some people have run multiple jamma boards from a single pc power supply.  I haven't actually done that, but I guess it's possible.

[Cisco Kid]

actually the Sparkle and some Antec PSUs have adjustable pots which control the 5V line ... you just have to take the cover off them to be able to adjust them and be care not to shock yourself  

[OSCAR]

actually the Sparkle and some Antec PSUs have adjustable pots which control the 5V line ... you just have to take the cover off them to be able to adjust them and be care not to shock yourself  

Yeah, figures...  I was betting that when I wrote that someone would mention there are certain brands/models of pc power supplies that have adjustable +5V output.  

As a general "rule" though, if you pick up just any old pc ps or scavenge one out of a used case, it most likely won't have an adjustment pot.  Or maybe I'm the only cheapskate that has no-name, generic power supplies laying around, too.  

[JoyMonkey]

Yeah, figures...  I was betting that when I wrote that someone would mention there are certain brands/models of pc power supplies that have adjustable +5V output.  
As a general "rule" though, if you pick up just any old pc ps or scavenge one out of a used case, it most likely won't have an adjustment pot.  Or maybe I'm the only cheapskate that has no-name, generic power supplies laying around, too.  

So basically, should I be trying to get a little more than +5V from the PC power supply? I've a couple of generic power supplies that I was thinking of using. I'm pretty sure their +5V output is around +4.8V, I'll need to test them to be sure.

Is there a good chance that 4.8V will do the job okay? I won't actually have the PCB to test for a week or so, I'm just trying to iron things out in my head first.

[OSCAR]

It depends on the game, but you will probably be okay.  Some old boards, like the Williams, are pretty sensitive to low voltage.  And since you have to send the +5V to about 4 different boards with those, the +5v can dip a bit.

I haven't had a problem running native jamma boards with a pc power supply, but the only way you will know for sure is to try.  If the voltage is too low, the game will probably just do flakey things like reset while playing and stuff like that.

[JoyMonkey]

Thanks for all the help, I think I've got the whole power thing into perspective. But now I've got another worry....

How will I get this to display on a PC monitor?

I've wired PC's to arcade monitors before. Is it just as easy to hook up a jamma harness to a VGA monitor? I've a feeling it won't be so simple. I'm guessing it'll depend on what resolution the arcade PCB uses.

If it can't be done, do you think an old Popeye monitor would work with Tekken2? The manual I found doesn't say what resolution/refresh the game runs at, so I'm not sure if it'd be compatible.

[OSCAR]

To connect RGB from a jamma board to a PC monitor, you can use an upscan converter like the XRGB-2.  A Google search for that device should turn up a retailer.  Or a rgb -> composite/s-video converter from www.jrok.com will let you run it on a TV.

If you happen to have an old NEC multisync or Amiga monitor that accepts 15kHz, you should be able to connect it right to the jamma board without doing anything.

I'm not too familiar with Nintendo monitors, but I think you may need to do a color inversion mod or something to make it work with jamma games, I'm not sure.

Anyway, there are lots of different ways to display jamma games, I only listed a couple.

[JoyMonkey]

Sure, you can do this.  In fact, I'm doing it here: http://www.arcadecontrols.org/yabbse/index.php?board=10;action=display;threadid=11924

I tested powering on an ATX power supply like you have done by connecting the 'power-good' to a 5v line and it worked fine.

But then I tried doing the same using the older power supply that I was going to use with the arcade PCB; it powers on for a brief moment (long enough for the PSU's fan to turn a couple of times) and then it powers back off itself.

Any ideas?

[OSCAR]

I've heard that some pc power supplies will shut themselves off, or may not be stable, if they don't have enough load on them.  I have to imagine that a jamma board would have enough load to keep a pc power supply stable, but you can try wiring in an incadescent lamp to the +5V so there is load present as soon as the power supply is turned on.

I can't guarantee this will help at all, but it can't hurt to try, either.  

[IceCold]

Sure, you can do this.  In fact, I'm doing it here: http://www.arcadecontrols.org/yabbse/index.php?board=10;action=display;threadid=11924

I tested powering on an ATX power supply like you have done by connecting the 'power-good' to a 5v line and it worked fine.

But then I tried doing the same using the older power supply that I was going to use with the arcade PCB; it powers on for a brief moment (long enough for the PSU's fan to turn a couple of times) and then it powers back off itself.

Any ideas?

Make sure the wires coming off the power supply are not shorted.  If I short the red and black or yellow and black wires together on my older power supplies, it will shut off and make a buzzing noise.  Maybe this is it?