Dual ATX Bench Power Supply

This is a dual bench power supply consisting of ATX and WTX computer power supplies, one supplying fixed voltages and the other supplying variable, and a dual USB power port all combined into one project case. Technically this could all be done with just one power supply, but I had these 2 lying around and decided to give them their own unique purpose. What's nice is they can be run independently of one another or together as they each have own power switch.

Parts List:

(1) Project case (Zulkit Junction Case Enclosure 12.6"x10.6"x4.7")

(2) ATX power supplies

(3) Mini voltage modules (Bayite 3-wire 0-30v digital voltmeter)

(1) Voltage/current module (Eiechip LED Digital Voltmeter/Ammeter)

(1) 2N3055 or MJ12005 NPN power transistor with heatsink

(2) 6-position barrier terminal strips

(1) 2500 ohm 2-watt potentiometer

(2) DPST Lighted rocker switches 120VAC (All Electronics CAT# LRS-42)

(2) Indicator lamps (I used vintage Dialco indicators converted to LED's)

(4) Banana jacks, 3 red, 1 black

(1) Double banana jack terminal block

(2) Fuse holders

(1) 12-pin connector

(1) Single or dual-ganged USB port(s)

Line up where the power supplies will go and cut holes for the ventilation fans, fuse holders, and line cord input in the rear panel. I modified the WTX supply by soldering external wires to the internal ac input and ran them outside the housing to power the ATX fuse and power switch. This avoided having to use two line cords, but you can certainly do that if you like. Install the barrier strips and fuse holders.

Mount the power supplies and power transistor/heatsink asm. Each power supply has multiple output wires coming out of them. Cut off the connectors then all wires except for one wire of each color: red (5V), yellow (12V), orange (3.3V), black (ground), and green (PS on). Connect the green wire to the black so that the supply will turn on when 120VAC is applied. The ATX I used had additional wires, pink (25.3V) and white (38V). Use the white 38 volt wire for the variable output. Connect the output voltage wires to the barrier strips.

The power transistor is used in conjunction with the potentiometer to vary the output voltage from the 38 volt line. This is a very simple and effective means of varying the output, you don't need any prefabbed voltage control modules for this unless you want to spend extra $$. See the schematic diagram on how to wire it.

All wires to the control panel are brought out through the front. I used 16 gauge wire for the power supply outputs from the barrier strips. A 12-pin connector was used for most of the connections from the panel to base. Small wire nuts were used to connect the mini voltage modules for easy replacement if needed.

Make all connections and verify operation.

Verify correct fan operation.