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The Reference Room
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Wired for Sound: Steve Lampen
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| Spills and Chills, On the Air |
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by Steve Lampen,
9.13.2006
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Steve Lampen is Technology Specialist, Multimedia Products for Belden Electronics Division. Steve holds an FCC Lifetime General License (formerly a First Class FCC License) and is an SBE Certified Radio Broadcast Engineer. On the data side he is a BICSI Registered Communication Distribution Designer. His latest book, "The Audio-Video Cable Installer's Pocket Guide" is published by McGraw-Hill.
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In an earlier column on the history of wire, I mentioned ancient batteries that used the first wire to conduct electricity. Inside these batteries, the liquid that made them run probably was grape juice.
So it shouldn't come as a surprise that grape juice, dumped into a broadcast console, doesn't help. If you dumped battery acid, it wouldn't work too well either. I've seen recent comments in newsgroups about what is allowed in studios - Coke, coffee, water, grape juice - and/or who gets charged when the console needs to be cleaned.
I've been talking with several people about this. What effect do these "chemicals" have on board traces or cable? Since this column is actually about wire and cable, I asked an organic chemist here at Belden, Jeff West, who said that even inexpensive PVC jackets were highly resistant to these liquids. As long as the copper inside is covered, the conductors are protected.
You might have seen old cable that had turned green inside. This meant the jacket and dielectric (core) didn't do a very good job of protecting the cable. In the old, old days it could also have meant that there was "compound migration," in which the chemicals in the jacket separated and oozed through the cable until they got to the core. You might still see this with some offshore brands.
Another aspect is how equipment, especially on-air consoles, is set up. Old boards used to mount parts away from the bottom of the console. I remember a Gates Yard and a Gates Executive that seemed amazingly impervious to spills.
But then came the fancy console with a motherboard and card edge connectors for the modules. Now you could hot-swap modules, but the design also meant that anything you spilled ran down the cards, into the card edge connectors and onto the motherboard.
Any board with card-edge connectors should be checked to be sure you have gold edge into a gold socket. If you put gold edge into a tin socket you now have a potential of 1.84 volts and a few drops of almost anything will start that battery running. Gold might not oxidize, but it also does not resist corrosion, reacting with other metals (how do you think they gold-plate cheap jewelry?). "Like-metal to like-metal" is the only way to get a ZERO volt reaction.
Pools
Mike "Catfish" Dosch of Axia Audio recalls working at PR&E where he saw "many a Coke spill ruin a console motherboard. The vertical cards didn't get so much damage as the exposure was minimal, just a bit of residue left behind on the liquid's journey to the bottom of the console. But the motherboards would get pools of liquid," he said. "The worst was soda, as it would eat away at the copper if left to do its nasty business - and operators wouldn't admit they spilled the Coke, so of course it would sit on the motherboard until something failed."
Designers are thinking about this stuff. Dosch said the Axia Element control surface, for instance, minimizes damage from spills. There's nothing on the bottom of the console pan; the modules are connected to a small distribution board in the meter panel area via Cat-5 cables. "We carry +48VDC power and signals - CANbus in this case - over those cables. I guess in the case of a very nasty spill, the jackets of the Cat-5 cables will be sitting in cola. Hard to imagine any damage that could be caused really; but if a cable is damaged, it is easily replaced. Click-click.
"Of course, we would much prefer operators not to bring their Big Gulp soda into the studio."
What's the acidity of common liquids found near your on-air equipment? Here's a list. (A pH of 7 is neutral. The lower the pH, the more acidic the solution.) Coke and other carbonated soft drinks have pH of 2.5. Diet Coke and similar carbonated diet soft drinks are 3.1. Orange juice and carbonated water are 4. Milk is 6.5. Neutral at 7 are water, flavored water and sports drinks. Coffee and tea are 7.5.
Jeff West tells me carbonation is a major factor in lowering pH. Carbonic acid is formed when carbon dioxide is dissolved in water. However, if you read a label of a soft drink, you'll often notice phosphoric acid and citric acid are also present, just to name a few. These also lower pH.
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