We Love That 'Mr. Clean Attitude'

by John Bisset

Aren't solid-state transmitters great? You just plug them in, and forget about them!

Too often that's what happens, unfortunately; and this "out-of-sight, out-of-mind" attitude eventually will cost you. Dirty air is no friend of the broadcast engineer and it can have a dramatic impact on the operation of solid-state transmitters.

Fig. 1: A sparkling clean heat sink is a happy sight.

It's not enough to clean or replace air filters. At least once a year, more often in dirty environments, the RF modules should be removed and their heatsinks cleaned. The easiest method is with a can of clean, compressed air and a damp rag. Avoid air from an air compressor, which contain oil droplets. The suction end of a vacuum can also be useful.

Of course, if you use the compressed air canister, do the cleaning outside the transmitter building; no sense in dirtying other equipment by performing the task inside.

The large heatsink surface area on solid-state modules must be kept clean to conduct heat efficiently. Allow a layer of dust and dirt to accumulate, and the cooling efficiency drops. Permit too much dirt to accumulate, and you may lose the solid-state devices in a module.

While you're cleaning, check the filter on the back of your exciter or IPA drawer. Keep in mind that if this small fan dies, you'll probably lose the exciter.

Fig. 2: Dirty fans reduce cooling efficiency.

So do you have a spare on the shelf? Replacements can be found from Granger or the exciter manufacturer.

If you're lucky enough to switch to a backup, and can really clean everything, turn the exciter off, remove the exciter filter and inspect the fan blades. Blades caked with dust and dirt reduce blower efficiency; the drag on the fan motor will expedite failure, as seen in Fig. 2.

Do a good cleaning of the blades with rags soaked in isopropyl alcohol to take care of the dirt.

I spoke recently at the Ohio Association of Broadcasters. One of the attendees pointed out that most cleaning alcohol that you get at a drug store can be up to 30 percent water. A pharmacy or medical supply store can supply 93 percent, or higher, concentrations. The higher concentration boosts cleaning power and reduces the time for water to evaporate.

Fig. 3: Mark high-efficiency filters with the date.

Before leaving the supply store, pick up a box of unsterilized cotton tipped applicators. They're cheaper than the sterilized version. The cotton is wrapped on 9-inch wooden sticks, making for a sturdy cleaning tool, especially when trying to clean dirt out of the bottom of tube sockets.

If you replace your air filters with the pleated, high-efficiency type, write the date on the side. Track of your filter usage. It helps you budget, and the date is a good reminder of just how long the filter has been in service.

. . .

Remote season is slowing down. This is a good time to perform preventive maintenance on your remote gear.

Inspect and repair any nicked or cut cables and broken connectors. If your microphone or speaker cables or snakes have been plastered to the ground with duct tape, the sticky residue can be removed by coating a clean cloth with 3-in-1 oil. Wrap the cloth around the cable, hold the cable taut and run the cloth up and down the cable several times. The penetrating oil will dissolve the sticky mess, and it will come off in the cloth. Remove any oil residue with a clean cloth, coil the cable and store.

Fig 4: Use colored electrical tape to identify cables

You can color-code the cable ends using colored electrical tape. Any electrical supply shop will have various colored electrical tapes. Invest in a few of the Velcro (or other brand of hook-and-fastener-type) cable ties, which will keep cables coiled and easy to identify. An engineer showed me how he wrote the cable length on each end of the XLR connectors, then used colors to also identify the lengths. The few minutes of effort made digging around in a cable box searching for a cable easier.

Don't forget a fresh box of 9 V batteries and a couple of Sharpie or similar brand of markers to date the batteries if you plan to use the equipment over the winter. If your remote gear will be enjoying a winter slumber, remove batteries and buy a fresh box when your remote season begins.

It won't hurt to spend a few minutes inside your Marti gear, too. Jeff Twilley, director of engineering for Delmarva Broadcasting, has found the biggest cause of Marti failure is dirty connections with the Molex connectors on each board. Typical connectors are shown in Fig. 5.

Fig. 5: Note plug orientation when removing plugs for cleaning

Jeff suggests that before you remove these plugs, note the orientation so the plug gets back onto the same pins. It's easy, in a rush, to get off by one pin, and you don't need those headaches.

Remove all the Molex plugs and treat the pins to a spritz of contact cleaner, or better yet, Caig Labs DeoxIT. Gently swab the pins to apply a thin film of this cleaner/preservative. Work the Molex plug back and forth over the pins to clean the contacts inside the plastic plug.

Again, make sure the plug is properly inserted onto the pins. Fire up the rig before replacing the top, just to make sure everything is working properly before storing the equipment for the season.

A little bit of preventive maintenance now will pay off with snag-free remotes in spring.

John Bisset has worked as a chief engineer and contract engineer for more than 30 years. He is the northeast regional sales manager for Broadcast Electronics. Reach him at (571) 217-9386, or jbisset@bdcast.com. Faxed submissions can be sent to (603) 472-4944. Submissions for this column are encouraged, and qualify for SBE recertification credit.