"The early bird gets the worm, but the second mouse receives the cheese."
The old age of the components is not the only cause of equipment failures. Another, more unpleasant, is the infestation of vermin, which will be common again now that the coldest climate is over much of the nation.
If you have not taken steps to place bait traps and moth balls around your remote transmitter site, now is the time. All kinds of animals are attracted to the heat of their transmitter building; and they will be installed quickly at home, sometimes inside or on your computer. See Fig. 1.
Fig. 1: DA parameters outside? No, the antenna monitor was being used as a mouse dependency. The upper vents of the monitor served to channel the liquid inside, destroying the printed circuit boards.
Stop the problem before it starts. Rodents like to travel along the walls; Place your glue or bait traps there to hook them before they enter the racks of your equipment.
Small black mouse droppings on the floor of the building or enclosure are a sign of action. If you find that your site has been infested, protect yourself while removing the nest and droppings. Wear gloves, a gown and, above all, a mask to avoid breathing dangerous pathogens in the air.
Fig. 2: A useful resource can be found at www.bestwaytogetridofmouseinhouse.com/mouse-infestation/#risks.
John Wells has written a useful tutorial on rodent-borne diseases and offers useful advice to ensure their elimination. The URL is in the title of Fig. 2. YouTube also has several videos; Look for "eliminate mouse infestation" for suggestions
Broadcasting engineer Tom Norman read with interest our discussion about Frank Hertel's experience with electrolytic capacitors in an FM exciter. It brought memories that may be useful for other readers.
Tom recalled an instance in which a remote control system failed. His tests could not give a reason, but his operation remained terribly intermittent. Tom decided to place himself at the transmitter site until he could find out what was wrong.
He started with the usual, checking the power supply voltages using a VOM. No problem. Checked the same power supply rails with the scope. There is nothing wrong yet.
At one point in the circuit, one of the power supply voltages was further regulated using a three-terminal regulator. When determining the output of that regulator, it struck the regulator with icy fog. The small amount of wave disappeared. Tom is not sure what he owned to verify the regulator's input terminal, but when he did, he saw a significant ripple. Why was there more ripple at the input of this chip than that present at the output of the regulated power supply that feeds it? He froze the chip again and calmed down.
Tom replaced the chip. No difference. It was then that he considered what was connected to the input and output terminals of the chip. You guessed it: there was a small electrolyte at the entrance. Tom replaced it. The power supply calmed down, but it still had an erratic behavior of the remote control unit.
Tom's next step was to freeze the fog of all active components. He was about to freeze an operational amplifier 741, but touched it inadvertently with the straw from the fog canister nozzle. The remote control unit went from erratic to totally dead. He touched the operational amplifier again, no difference. He froze it. Return to erratic operation. Tom replaced the operational amplifier. The operation was still erratic. Checking the scheme, he observed the electrolytic capacitors bypassing the power supply at the power supply pins. Tom replaced those capacitors. Still erratic.
Taking out the little that was left of hair, he removed the operational amplifier and inserted a new one. Problem solved.
All this happened shortly after a major thunderstorm during which Tom had witnessed multiple direct attacks on the tower.
Although not sure, Tom sees two problems here. One is that lightning can affect the components inside a circuit, where you would normally expect them to be safe and sound. His conjecture is that electrolytics, being old, failed due to the exacerbated influence of lightning. Then, for reasons that you cannot understand, one or the other of the bypass capacitors of the power supply of the operational amplifier became inductive and caused oscillations whose maximum voltages exceeded the limits of the operational amplifier 741, so it became cold. Although this is speculation, it reminds us that electrolytics should be replaced every seven years or so.
Tom also remembers that, as a station engineer, when he found Mallory brand electrolytic capacitors in a computer, he shot them all. He said he had had such difficulty with Mallory's electrolytic capacitors that he specified that new equipment should not contain electrolytic capacitors from that manufacturing.
Tom writes that he still has this prejudice, even while acknowledging that things may have changed since then. Now he doesn't do much bank work, but he will occasionally design small circuits to use in his home environment, and when he asks for capacitors, he selects another manufacturer, which is fun, because Tom has never had a Mallory Sonalert fail.
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John Bisset has spent 50 years in the broadcasting industry and is still learning. Manages radio sales in the western United States for the Telos Alliance. He has the CPBE certification with the Society of Broadcast Engineers and has received the SBE Educator of the Year Award.