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Upgrade an Optimod Power Supply

Plus, energy-efficient lighting products

Fig. 1: The dead Optimod supply. When the switching power supply used in Gary Morgan’s Optimod 8200 (Fig. 1) died, the OEM replacement would have cost around $600. He sought to find another solution.

If you’re still using the original power supply module, the small switching power supply may go bad. This little supply can be replaced easily and re-soldered for about $75 (Artesyn NFS40-7608), but with a lack of adequate cooling, it will be gone again in a couple of years.

Gary got the idea of replacing this supply cheaply by using an ATX computer power supply. It comes with its own cooling fan. Naturally a 300-watt ATX computer supply won’t fit into the 8200 processor box, but it does sit on the top nicely and doesn’t take up much space in your rack.

As long as the original 8200 15 V linear supply is in good shape, this ATX switching supply will last for many years. Any decent 300-watt ATX computer power supply will work just fine. You’ll be using the +12 V, –12 V, +5 V feeds, as well as the circuit grounds.

Pull the fuse on the original Optimod switching supply, and leave it in place. You can then route your computer supply wires through a small hole drilled in the back of the original supply. The voltage feeds are then soldered to the TP (marked test points) on the original power supply board.

Gary soldered his wires first to the TPs in the box, as seen in Fig. 4, and then attached the wires to a Molex plug (Fig. 3). This way, the ATX supply can be disconnected from the Optimod if needed. You “turn on” the ATX supply by shorting its green wire to any black (ground) wire. You can use an external switch, short or solder your wires to the internal Optimod on/off switch.

Fig. 2: The new supply sitting on top of the Optimod. The supply connections are as follows:

+12 VDC (Yellow) — TP-11
–12 VDC (Blue) —TP-8
+5 VDC (Red) — TP-10
Grounds (Black) —TP-9

Gary has two 8200s that have been running on ATX supplies 24/7 for more than five years.

Robert Gonsett, editor of The CGC Communicator newsletter, writes in a recent issue that the FCC’s Enforcement Bureau has done a wonderful job of reorganizing its field actions list into year-by-year pages.

This means you no longer need a supercomputer to download years of data just to see the most recent enforcement actions. Kudos to the commission staff for getting this done. Visit

And thanks to Robert Gonsett for getting the word out.

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Craig Pringle started his electronics career as a hobbyist, “playing radio” with a rented Wollensak reel-to-reel and a low powered Allied/Knight Kit three-tube AM transmitter (Model 83Y706). After graduation, Craig worked at a variety of stations.

Being around all that broadcast equipment he caught the engineering bug, which led to a First Class License and, eventually, the formation of Telfax Communications, maker of the first truly compact telephone remote audio mixer.

Craig’s latest venture is, where he specializes in energy-efficient lighting products for commercial and industrial applications.

He has used the lettering process we outlined in the March 1 column, “Your Panel Lettering Made Easy,” but instead of printing on paper, he uses aself-adhesive printing media known as BestPrint, made by Chartpak.

The product is a thin opaque white appliqué film (8.5-by-11-inch sheets with peel-off paper backing), which works nicely in laser printers and copiers. An inkjet version is available.

The finished product is durable and trims up nicely using an X-Acto knife, resulting in a professional appearance for any project.

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Fig. 3: A Molex plug is inserted in-line for quick disconnect. Paul Sagi sends his regards from Kuala Lumpur, and offers a really slick resource for Workbench readers using Google Chrome.

All radio engineers who use the Chrome browser should have a look at CircuitLab, an extension for Chrome. You’ll find the link at

CircuitLab is a schematic editor and circuit simulator. It lets you build and test circuits right in your browser. Use CircuitLab to design circuits with their easy-to-use schematic editor. Then perform accurate analysis in seconds.

Fig. 4: Solder the wires to the Optimod test points to complete the modification. The software provides beautiful schematic printouts in PDF form. Watch the video for an idea of what the tool can do. If you do any kind of circuit design, this tool is a must.

Paul also sends a link for multiple virus scanners. Not all virus scanners will detect every virus every time. Thus, it’s best to use multiple virus scanners. However that’s usually inconvenient — until now. The URL is also on our links page.

Contribute to Workbench. You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to [email protected]. Fax to (603) 472-4944.

Author John Bisset has spent 44 years in the broadcasting industry and is still learning. He handles West Coast sales for the Telos Alliance. He is SBE certified and is a past recipient of the SBE’s Educator of the Year Award.