Introduction: Bench Power Supply

By Ongoing Projects
About: Professional work in various electrical and mechanical fields, obscure sense of humour and typically willing to help... Currently under contract designing environmental monitoring equipment.

Re-purpose a Computer power supply into a Quad output Bench supply.

I have been using this to test a multitude of different circuits and devices!

Step 1: Materials

You will need to know basic soldering skills.

A computer power supply.
Several eyelet wire connectors.
different coloured binding posts.
An LED(i used an old computer power led)
Power resistor. 10Ohm 10W should work.

Optional is a cigarette lighter adapter (CLA).

Step 2: Disassembly

Observe proper precautions when disassembling a power supply.
Make sure it is not connected to mains
Make sure that it is fully discharged.

Remove the cover screws.

Remove any chassis connectors.
Remove the mainboard screws.

Remove the power supply circuitry from the metal chassis.

Cut all the output wires to about 6-8 inches from the mainboard.

Step 3: Identify and Connect

The output section of the main circuit board may be labeled. If it is not The following rules may apply.

Red = +5V
Orange = +3.3V
Yellow = +12V
White(as shown) = +12V
Blue = -12V
Purple = not used
Grey = Power on LED
Black = Common or Ground

Thin orange = 3.3V sense
Thin Red = 5V sense
green = Power on

Separate and bundle the wires accordingly.

The sense wires on my supply are directly between the orange and yellow in the picture.

Group the wires together and fasten them with solder or crimp eyelet connectors.

Any exposed connections should be covered with heat shrink to taped to prevent shorts.

The green wire must be connected to ground.

the thin orange must be connected to thick orange.
The thin red must be connected to thick red.

You should connect a resistive load (some supplies require this for proper operation). I chose a 10Ohm 10W power resistor. it needs to be connected on one end to the 5V red wire and on the other to ground. I soldered this in place then protected the conductors with heat shrink.

I chose to use a CLA and wired this directly to the 12V (white) V2 section of the supply. The ground was connected to a black wire.
The CLA was positioned into the existing wire loom hole in the back of the supply. It is held in place with a rubber grommet.

If you choose to you can connect an LED between the grey wire and ground. use an appropriate sized resistor for your LED,

Any unused wires should be sealed from shorting by covering the exposed ends with heat shrink or electrical tape.

Step 4: Drill the Chassis

You will want a nice way of transferring the power from the inside to the outside.
I used binding posts. The colours chosen were all that the local store had in stock.

Drill holed in a convenient place on the chassis to attach the binding posts to. The rear of my supply was the only place.

Secure thee binding posts to the chassis using the nuts provided.

Drill a hole in a convenient place for the LED mount.

I drilled using standard bits and a step bit. If you haven't used a step bit before, you are definitely missing out on the joys of nice round holes in sheet metal.

Step 5: Test and Enjoy

Test the power connections with a multimeter.

Once you have verified that there is no short and the voltages are placed to the binding posts that you wish, reassemble the chassis.

Label the binding posts for future reference.

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