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ATX to Lab Bench Power Supply Conversion

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Step 4: Connecting front-panel items

Here, I am connecting the appropriate wires to the binding posts, power switch, fuse holder, and LED's.

In an ATX power supply, there should be a wire that is used to turn on the power supply. You can see this wire (It's green) in the second picture; it is the green wire in the middle, where it says "ON/OFF" on the PCB. I connected this to the switch, and the other pole of the switch went to ground. The +5, +12, and -12 are connected right to their wires on the PCB. The ground wire is connected through the fuse holder before the binding post.

Initially, I was going to use green LED's, but I realized I had many more red LED's than green LED's, so I switched them over to reds. In the first picture, you can see the holders I installed into the front. I connected the LED's through a common resistor to ground. The LED on the left (from the front view) is a standby LED. It is lit whenever I have the power supply plugged into the wall. It is connected to the +5V standby wire on the PCB. In my PS, it's purple. The other LED is the "Power On" LED, and it is lit when I have the power supply turned on. It's connected to the "Power OK" signal wire, which goes to +5V when the power supply detects that it has stabilized the voltages. In my PS, it's the gray wire.
 
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seraine2 years ago
For some reason, my standy led takes about a minute to turn off when it loses power because it takes a while for the voltage to drain off. Is anyone else experiencing this, and is there a simple solution?
This is likely because of the inductors and similar components found within the psu. When on they build up a large magnetic field so when turned off the field collapses and produces current which will keep the LED on for a short while.
matthewbeckler (author)  seraine2 years ago
I see the same exact behavior when I unplug my PSU. I don't know if there's a way to change this behavior, but I also can't think of a reason why it would be a problem.
NiKiToS3 years ago
I have no writing near green wire which says on/off and it doesn't say PGS near the gray wire, it does say +5v SB near my purple wire... should i just ignore the fact that it doesn't say it, and carry on with your arrangement, or search for another PSU?
matthewbeckler (author)  NiKiToS3 years ago
Hi NiKiToS, thanks for the comment!

Since all three wires of interest (green, gray, purple) should be in the main ATX power plug, you should be able to give this PSU a "test drive" without doing any mods.

Try connecting an LED-resistor in series between the purple wire and a black (ground) wire. You could use any resistor between 220 and 1000 ohms. The longer lead of the LED should go to the purple wire, the shorter lead to one side of the resistor, the other side of the resistor to a black wire. The LED should light up when the PSU is plugged in, but still off.

Next, try putting a wire between the green "on" wire and a black wire. This should turn on the PSU and hopefully the fan (if any) will start up and begin to spin.

Try the same LED test for the gray wire, which should light up when the power supply is properly turned on.

Those quick tests should help you identify if the colors are correct, and if you'll be able to use this power supply. Good luck!
hyratel4 years ago
You know, it really does help if you put all this effort into a WORKING psu, instead of a dead one. </frustrated>
theyikes6 years ago
Sweet! Finally I have a use for my ever increasing stock pile of PSU's! keep up the great work and keep the ideas flowin'! Cheers!
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