What’s Lurking Behind Electrical Panels?

Fig. 1: Open your electrical boxes periodically to see what’s inside …
One of the nicest things about the NAB Show is catching up with old friends you don’t get to see the rest of the year. Steve Franko falls into that category for me. Steve is a contract engineer for two groups of stations in Idaho. Many of his sites are inaccessible for part of the year due to snow; routine maintenance often is abbreviated.
Recently Steve was called to a high-power FM that was off the air. He discovered a burned breaker panel that had gone bad on a three-phase circuit. The transmitter had promptly shut down after losing one of the phases.
Fig. 1 shows what Steve found when he opened the disconnect panel. Judging from the middle wire in the box to the right, the panel had not been checked for at least 15 years.
The damage resulted from a not-quite-tight connection from the original installation. Time marches on and so do its offspring: heat and corrosion. The green corrosion and burned wires can be better seen in Fig. 2. Steve said the owner was lucky that only the wire and not the entire box burned.
Let this be a warning to tighten all electrical connections every couple of years, at least. The services of a licensed electrician are well worth the investment, considering what could happen. 
Fig. 2: You may save yourself an off-air emergency, maybe even avoid a fire.
While your electrician is handling the electric panels, why not perform the same tightening regimen on wiring lugs and connections inside your transmitters, and, for AMs, phasors and antenna tuning units? You might be amazed at what this service will uncover, especially inside transmitters with vibrating blower motors. Connections won’t stay tight forever.
Remember to have your cellphone camera ready too. Tell the electrician you want to take a picture of anything out of the ordinary. Send it not only to us at Workbench but also to the station general manager or owner, to remind him or her of the great job you are doing maintaining the company’s investment. Thanks Steve for a great maintenance reminder.

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Bob Groome from ERI passed along a link to a really cool way to build a transmitter. See the RW links page for this issue.

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Scott Dorsey is an independent engineer who handles a dozen or so stations in the Williamsburg, Va., area. He read our tip about using colored duct tape (April 25) and wrote in with a plea for engineers to spend the money and buy real gaffer’s tape.
Gaffer’s tape is available at your nearby theatrical supply store or over the Web, in a variety of colors. It’s designed for gaffing cables down. Best of all, as Scott points out, gaffer’s tape does not leave gooey residue all over your cables and wires as duct tape will.
All great points; yet if you’re on a budget, or if duct tape is all you can find for that last-minute remote the sales staff sold, all is not lost. Pick up a can of WD-40 penetrating oil. It does wonders cleaning off that sticky duct tape residue; and it cleans quickly. 
For more uses of WD-40, head to their website. Also visit http://radioworld.com/May-23-2012 to discover more than 2,000 uses for this product.

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Have you been to the SBE webinar site? A variety of webinars are archived at www.sbe.org, including one on “Springtime Maintenance.” Plus, SBE members can view the ’nars “on demand.”
I had several engineers remark that this webinar was like a “live Workbench column,” with plenty of tips to get your site ready after a long winter. SBE is making continuing education easy with these on-demand webinars. Visit the site today and feed your mind.
Contribute to Workbench, You’ll help your fellow engineers and qualify for SBE recertification credit. Send Workbench tips to johnpbisset@gmail.com. Fax to (603) 472-4944.
Author John Bisset has spent 43 years in broadcasting industry and is still learning. He is SBE certified and a past recipient of the SBE’s Educator of the Year Award. He recently joined Elenos USA, an FM transmitter company.

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Comment List:

When checking connection in an electrical panel I have often used a "Spot Infrared Thermometer" something with a spot/distance ratio of 1:8 or better (8-inch distance = 1-inch spot). Craftsman makes one for about $80. I also find it useful in checking tuning coils and other RF components for overheating in a phasor or tuning unit - but sometimes the high RF field interfers with the readings - so that's another consideration you should keep in mind when selecting a spot infrared thermometer (rf immunity/shielding).
By Tim Sawyer on 5/18/2012

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