Arcade PSU -> Test Bench PSU?

[bkenobi]

I'm not sure if this is the best section, but it should get the most views...

I've seen some DIY mods to convert an old ATX PSU into a lab test bench.  They seem easy enough, but then I thought, why can't I just take an arcade PSU and use it directly?  It already has connections for +12v/+5v/Gnd as well as A/C.

Can anyone post a link to someone that has done this or suggest why it's a bad idea?

[BobA]

It makes a small bench power supply and is simple to wire so why not.   ATX supplies usually provide the same voltages at higher amperage but there are no easy way to wire them without taking the harness apart. They also need the power on jumpered to ground or switched to ground with a switch.

[MonMotha]

Typical PC supplies require a small load to run.  This and the lack of an adjustable current limit can make them difficult to use as a real bench supply, but they're generally going to be fine for testing arcade boards and such. I actually have an old ATX supply in one of my arcade cabinets.

Be aware that you can pull enough current off some PC supplies to make a fairly decent welder.  If you mess something up but don't kick the supply into shutdown, the results can be rather spectacular (and melty).

[bkenobi]

Well that sounds like a couple votes for "yes" as a decent cheap bench power supply.  I'm primarily looking to test small circuits (such as for an Arduino).  Is there an easy way to limit the current so I don't fry things?  I've seen a bunch of DIY ATX mods that look nice, but there are just as many posts that say "be careful".  I'm a mechanical engineer so the main think I know about EE is that once the magic smoke comes out, you have to start your project over from scratch!  I've done plenty of tinkering, but I don't have much formal training beyond sophomore year of college.

[MonMotha]

I can't think of a good way to really limit the current from a PC supply to the levels your talking about that aren't kinda complicated.  You could just use a low value, highish power resistor and accept the small voltage drop that will occur in normal operation (e.g. a 5ohm resistor on the 5V line will limit you to 1A but drop about 50mV at 10mA, which may be OK).

At the power levels you're talking about, you'll definitely need a dummy load to get the supply to run.  An old PC hard drive works great and is easy to hook up.

[bkenobi]

The biggest advantage of the Arcade PSU is that it's already good to go for a bench PSU since the power is already there and easy to wire to.  The disadvantage is that it does not have the negative VDC that the PC PSU has.  Looks to me like the Arcade PSU has +12v, +5v, gnd, AC1, AC2, AC Gnd.  A PC PSU has +12v, +5v, +3.3v, gnd, -5v, -12v (and can also provide 24v, 17v, 8.3v, etc. by using a voltage as ground).  I guess the AC could also be brought to the panel if desired.  But, the PC PSU requires a little work and apparently doesn't provide all that good quality power from what I've read.

Now that I think about it, having those other power choices would be kinda nice, so maybe I'll just bite the bullet and build one with a PSU I have sitting around in the basement.  I gave away my only arcade PSU a few years ago, so I'd have to buy one anyway.