myork

My Feedback: (3)

Does anybody have a schematic for converting a ATX Power Supply to a 12 volt, 4.8 volt power supply with an on off switch. I've looked around and all I have found is people describing how to do it.

Thanks

Andrew

http://web2.murraystate.edu/andy.bat...OWERSUPPLY.HTM

There are only a few connections to be made:

Add a 10 ohm 10 watt load resistor or 1157 auto lamp across the 5v rail: red --> resistor --> black

Add a SPST switch between the PS_ON line and ground: green --> switch --> black

If there is a sense wire (brown or lighter gauge orange) attached to one of the 3.3v (orange) lines on the motherboard connector, it must be reconnected when the motherboard connector is cut off. Some supplies may have sense wires on the 12v, 5v or ground rails -- if there are, these should also be reattached to the corresponding lines.

Some less expensive supplies use wire gauges that are lighter than the industry standard recommendations. If you wish to have maximum power on the binding posts, attach two black (ground) wires to your ground post, two red (5v rail) to the 5v post and two yellow wires to your 12v post. Be sure none of the binding posts are grounded to the PS case.

That's about it.

vicman

My Feedback: (10)

Pictures are worth how many words?

myork

My Feedback: (3)

Thanks Guys!

I acutually just blew mine up[:@] I was trying to read current from one of the 12v sources to ground and I didn't load it first. I just put the red lead of my meter to the +12 and the black lead to ground and BOOM. Oh well atleast it was free

Andrew

myork --

I don't think you damaged your PSU. You can't measure current on this type of supply directly with an ammeter. You can measure the current being drawn by an attached device, however. Your ammeter has a shunt whose resistance is measured in milliohms -- essentially it is a piece of wire with a known and very low resistance and your ammeter quite literally measures the voltage drop across the shunt.

When you touched the meter leads to the output rails, there probably was an arc and pop, then the PSU shutdown. The overload circuitry kicked in -- you PSU treated the shunt as a direct short and cut off. Unplug it, let it sit for a minute, then it should power up again.

myork

My Feedback: (3)

Man I just tried it again and it still will not come on. After it shut down the first time it smelled burnt. I would say it is done.[:@]

Andrew

Yeah, it may be -- that burnt smell is usually a pretty good clue. You might do a visual for any open wires or a blown fuse -- normally, the overload circuit will capture and no damage occurs Hard to say what happened in this case.

myork

My Feedback: (3)

Yeah I feal like and idiot for not putting a load on it first. Oh well I got three more today for free The school I go to is throwing away some old PC's so I told them i would take em.[&:]