View Full Version : Computor PSU How to switch ON

11-23-2003, 11:19 AM
I got a few diffent PSU from a friend, I was wondering if anybody new what wires to connect up to get it to switch ON.

If I had the mother boards I could trace it but all I have is a load of wires.

I have identified all the power wires easily enough, and I have a green one labelled on the board On/Off.

This supply is a 230w made by DAN.

11-23-2003, 11:48 AM
Hi Xairflyer,

If this is an ATX power supply, the simple method is that you need an ATX motherboard. Then the power on function is provided by hooking your power on button to the terminal block on the m/b marked "Power on switch".

I suspect from your description, that your old PS was an AT style, which had its own mechanical switch?

11-23-2003, 12:07 PM
I usually put a small car bulb across +5V - Ground to get the supply to switch on (just for testing purposes). It won't produce power if there is not sufficient load.

11-23-2003, 12:47 PM
I assume you would like to use it to power a cnc driver board. It sounds like a ATX powersupply.

You need to tie the green to a black to get it to turn on. A resistor on the +5 volts helps a lot too. 10 ohms 5 watts works good.


11-23-2003, 02:28 PM
They are ATX power supply's, tried grounding the green ON/Off wire and adding a 12v bulb across the 5v but nothing on all four of the PSU I have.

From what you are saying above, Does all Computor PSU need a load before they switch ON.

11-23-2003, 02:49 PM
You should be able to turn it on without the load across 5v. If you have the atx connector handy, just double check that the green wire is pin 14. On some of the older psu's there is also a "power good" wire that may or may not need to be connected. If the fan twitches a little bit when you try to turn the thing on, chances are there is a short circuit somewhere.

11-23-2003, 03:10 PM
Yes the green is pin 14.

Power good !! Yes have one of them too, wondered what PG stood for it is coloured grey and is Pin 8

11-23-2003, 03:19 PM
Actually, it does seem as the power good lead may not be required, according to this page (http://www.xlr8yourmac.com/systems/ATX_PS_in_8600_9600/ATX_supply_in_8600_9600.html).

11-23-2003, 04:18 PM
Thanks Kong for the link

Right I connected a 4r7 17w resister across the 5v and grounded the green wire. Still nothing happens.

Tried the resistor on the 12v no good, tried the same on the othr ATX supply nothing either.
The 230w version has a grey power good wire but the 200w dosn't so I'm still stuck.

Going to add at the bottom of my posts from now on:

Lesson 11 - You think the software is the hard part, until you try to get your power supply going !!

Only joking Balsaman !

12-01-2003, 07:42 AM
Dell PSU's are Proprietory and do not follow ATX Standards, the pins are not in the same spot, they are also not the same color as standard ATX PSU's. A /few/ DELL PSU's are standard, but few and far between.

To turn on a /standard/ ATX PSU' Just connect the Green wire to any Ground (Black Wire), all the grounds are the same, so it doesnt matter which one. If your PSU Requires a load to run, simply connect an old Hard Drive to the Power Supply. However, in most most cases a load is not required.

For DELL PSU's, please read the following website...

Hopefully this helps some people out.

12-01-2003, 07:46 AM
Depending on the PS you might have to have load on both the 5+v and the 12+v. I am using 3 dell 'Server' power supplys and I had to have load on both plus a jumper from the green lead to ground.

04-04-2006, 11:08 PM
Check this out!


I've successfully modified an atx power supply as per instructions from that site.