Power Supply Q's

[SavannahLion]

I remember finding a page I think someone linked to from here that gave some information on Arcade Power Supplies. I don't remember exactly how detailed it was, but I think it's where I learned about err... the name of that really good power supply that I promptly forgot. Does anyone know the page I'm talking about?

I have about four or five arcade power supplies. I don't think they're the "good" models but they seem serviceable. I just want to read more about them before I plug them in and smoke them.

In the same breath, I think I remember information here on the forums about people using PC PSU's on Arcade boards. I have known good PC power supplies and it would simplify board testing if I know the board itself is good before I attach an arcade PSU to it. According to the JAMMA pinouts, I don't see a problem with grabbing the voltages I want and I imagine a PC PSU has far and beyond more power than an arcade board would require. Yet I don't see a lot of people mentioning that they use PC PSU's. Any particular reason for that?

[Kevin Mullins]

I don't see a problem with grabbing the voltages I want and I imagine a PC PSU has far and beyond more power than an arcade board would require. Yet I don't see a lot of people mentioning that they use PC PSU's. Any particular reason for that?

It's not a problem using a PC power supply as you described.
The only thing to keep in mind is some games require a -5v and honestly I just can't recall all the voltages on a pc power supply at the moment.
As for the second part of your statement..... I'm guessing that most people here are building MAME style cabs and are already using a complete pc including it's power supply therefore it never even becomes much of a question.

All you really need to understand on those arcade power supplies you have is that there is an AC input, then a +5VDC, +12VDC, Ground and sometimes the -5VDC output. (not all have that) You can simply wire up a cord to the AC input and then measure all your outputs to see if they are within range.
Some of the bigger arcade power supplies, usually has a built in power switch and or breaker, also include an isolation transformer and power for the monitor and marquee light.

Do you have any specific question?

[MonMotha]

ATX and AT PC power supplies do have a -5V rail, and also a -12V rail (which would be unused in an arcade setting).  My cab is powered of a PC supply, and a friend has a PC supply in one half of his Daytona twin: it replaced a dead venerable Peter Chou, which, to be fair, had coke spilled in it.

PC power supplies are in general overkill for most arcade applications, but that's OK.  Just remember that some PC supplies require load on both the 12V and 5V rails, while many arcade applications only really load the 5V rail.  PC supplies in general just shut down if they cannot regulate due to lack of load, so you don't have to worry about damaging anything.

PC supplies usually have the ratings for each rail written on the side and often even have an indication of what color wire is used for what function.  Make sure the supply meets your requirements in terms of current output for each rail.  This generally isn't a problem, but it's easy enough to check.

[knave]

I just read that PC power supplies might not be able to supply enough -5v to boards that use it.  Is this true?  What are some common/possable issues we might face if we wanted to use a PC supply for a standard Jamma cab?

[MonMotha]

PC supplies are fairly limited in current capacity on their -5V rail, but I've never encountered a modern (JAMMA era) board that uses much.  Most noted for using it at all (many don't) are Midway sound boards, which only use it for small signal amplification (preamp) and active filtering.  Most PC supplies are good for at least a few 100mA on the -5V line, which is good enough for these applications.  I've seen various arcade supplies and many aren't capable of much more, though some are.

The most common thing people run into with PC supplies is turning the darned things on.  AT supplies are easiest since they have an external 120V switch that you can just turn on (or jumper the wires together using butt splices or similar), but I don't like having 120V floating around if I can avoid it.  ATX supplies aren't too tough, really: just take the "PS-ON" (sometimes called "remote") wire and tie it to a ground pin with a short length of wire.  This will make the supply be "always on".  If you'd like a switch, you can put a small switch in there.  This switch only needs to be capable of switching a few milliamps as it is only a signal (much like your control panel buttons) and is not actually switching power lines.

Another thing to remember is that all PC supplies tie their power common ("power ground") line to the AC safety ground ("earth ground").  This can sometimes cause problems due to ground loops or the rare monitor that expects fully floating inputs.  Most people recommend tieing these together at the power supply, anyway, unless you have a reason not to, so this isn't usually a big deal.

[knave]

How do we tell if a pc supply will run with "no load"? 

So is it as simple as wiring the correct voltages to a terminal strip and hooking it into your harness?

I'm pretty sure either an AT or ATX would work...I have a few of each.  Would you say I'd be better off using the ATX and shorting the power switch wires?