Occasionally we query Workbench readers as to the most useful piece of test equipment; the cellphone camera usually wins out.
Dan Gunter is the owner and principal broadcast engineer of Alabama Broadcast Services LLC. He shares photographic proof of the immense value of a phone camera, not only for documentation purposes but as a tool in troubleshooting.
One of Dan’s client stations recently experience a mysterious trip of the 100 amp AC circuit breaker that fed the high-voltage power supply (HVPS) on a Harris HT25FM transmitter. Unfortunately Dan was out of town that day, as was his backup colleague Terry Harper.
Thus it was the station’s chief operator/assistant GM who wound up running over to the site. With instructions from Dan he reset the tripped breaker, which got the transmitter back on the air without a breaker re-trip.
Dan had experienced a similar off-air trip with another of that client’s transmitters, a problem that kept occurring sporadically. This was resolved by giving the arc gap in the HVPS some much needed attention — cleaning and re-spacing the gap per the manufacturer’s specifications.
Because that had worked earlier, Dan decided to do a “wee hours of the morning” shutdown on the trouble transmitter and check the arc gap. He found that it was at 0.3745 inches, nearly twice the recommended setting of 0.1875.
As pictured above, Dan noticed that the HVPS had a considerable amount of dust and debris, so he decided it was time for a thorough inspection and good vacuuming. After turning off all AC breakers and discharging the components, Dan set out to work.
Unfortunately, there are some places you simply can’t see without spending another half hour or more to remove the rear cover from the power supply, such as behind the transformer, choke and filter capacitor. Dan’s solution was to use his phone’s camera to shoot photos in the hidden crannies.
And that’s when he found the little problem seen here:
In case it isn’t clear what’s amiss, the image below offers a closer view behind the capacitor.
Dan says he doubts this was a factory-installed part.
Apparently, this rat snake had managed to crawl into the power supply through a gap at the lower left corner of an ill-fitting front cover on the cabinet. Dan suspects the critter managed to slither across a couple of wrong points in the HVPS and had a really bad day, also tripping the breaker.
Rat snake or not, Nautel’s Jeff Welton calls them all “rattle-headed copper moccasins.” And they don’t belong in transmitters.
Dan sent the assistant GM photos of his findings and work; he also put the dearly departed critter in a box, labeled it and placed it on the desk in the transmitter building, where the manager could inspect the evidence first-hand and dispose of it as he wished. (Let it not be said that Dan takes things from client sites without their approval.)
Dan visited the site a few weeks later and the box was still sitting on the desk, unopened. Imagine that!
As an engineer, you see a lot of strange things. Take pictures of these encounters to help management understand your value.
At one station where I was chief, I put a small bulletin board in the station lunchroom, and posted a “Picture of the Week.” from my site visits. Try it and see the reaction.
Shine a light on it
Like many engineers, as I’ve gotten older, I’ve required more “light” to see details like the numbers on a chip or a resistor color code.
Here is a flexible LED garage light, a replacement “bulb” that actually consists of three adjustable panels and screws into a standard light socket above my garage workbench, throwing off 6,000 Lumens!
Fig. 5 shows some of the possible configurations.
Find it at Amazon, it’s the best $36 you’ll spend.
John Bisset has spent over 50 years in broadcasting and is in his 31st year of Workbench. He handles western U.S. radio sales for the Telos Alliance. He is a past recipient of the SBE’s Educator of the Year Award.
Workbench thrives on your snake stories and tech tips, which count toward SBE recertification. Email [email protected].
