The power supply is often the first component to fail in broadcast equipment, whether due to line surges, overheating or component aging.
A client of Frank Hertel had a console with an internal switch mode power supply that provides +15 and –15 VDC. The supply needed to be replaced but Frank wanted to minimize the downtime and sought a workaround.
This is a simple way to retrofit the internal supply. Fig. 1 shows the parts you’ll need. In this case the console was a DMX Mix, but this suggestion may help with any similar supply in consoles and indeed any equipment that needs a small modular power supply.
Laying power bricks on top of the chassis may not be the most elegant, but Frank’s retrofit would let you cope with any future failures in a matter of minutes without the need to remove the chassis from the rack. Because the retrofit supplies sit on top of the chassis, they can be replaced easily.
Frank chose two separate, off-the-shelf 15 VDC power brick supplies. These are inexpensive and connect quickly to the original internal power supply cable, which you can adapt for this project. One power brick will supply +15 VDC, the second supplies –15 VDC.
The first step is to remove the original internal power supply, along with the supply jumper cable that connects to the motherboard pictured in Fig. 2; you can see how it connects from the power supply to the mother board. Make note of the polarities, colors and connections before removing.
Once the project is completed, the retrofit power supply cable will exit via the chassis cutout (where the original AC power cord connector of the original supply was located). Adding a rubber grommet prevents the edge of the chassis from abrading these wires.
The second step involves cutting the original power supply jumper cable in half, then extending each of the two halves of the colored wires to a length of 18 inches. This will give you enough cable to extend the cabling outside the chassis, for connection to the power supply bricks; see Fig. 3. Use the same color wires when you extend the wires, so there’s no confusion.
Pay close attention to the wiring of the 3.5 mm female connectors (Fig. 4) as they will route the appropriate DC voltage to the mother board, when plugged into the AC bricks.
The third step is optional. Frank could have plugged both supplies into individual AC outlets; instead he fashioned a junction box that ties the two supplies together. Construction of the junction box is straightforward, as pictured in Fig. 5; now only one AC power cable is needed. Upon completion, both power bricks and the AC splitter can be set upon the top of the chassis.
Have you replaced OEM supplies this way? Tell readers about your experience. Email your suggestion to me at [email protected].
