RADIO EQUIPMENT CARE

VIBRATION

It is very important to make certain that your receiver is not subjected to excess vibration from the engine in your model. The common practice is to wrap the receiver in soft foam and stuff it into the fuselage. However, the new design of receivers have several, up to five, components that are very easily damaged, or change values to affect a receiver's performance when subjected to vibration. The best method is to make a box or tube of soft foam plastic or rubber, and make it a size that allows a little movement for the receiver. Then, wrap the bundle with masking tape, not rubber bands, as these compress the foam, and reduce the insulation from vibration. Finally, make absolutely certain that the servo and battery wires emerge from the bundle at the opposite end from the antenna.

REVERSING SWITCHES

I have had many transmitters with channels not working or with travel jammed at one end. Many times this is due to a channel-reversing switch not being set correctly. Some transmitters have very light action reversing switches that can change position very easily. Check to make certain that all the switches are at their end positions, and toggle them several times to help keep the contacts clean. If the channel is still bad, then it is usually a problem with the respective stick assembly, usually the pot or its wires.

TRANSMITTER BATTERY PACKS

I hate to see the familiar method of installing transmitter NiCd packs using unreliable snap fasteners rubbing on spring leaves. Too often I have seen these corroded and lacking tension, with corrosion down inside the press studs parts. It is my practice to change all of these battery connections with two heavy-duty two-wired connectors which make a safe and easy to replace pack. I also get to the isolation diode, which will prevent cycling, or load testing of the internal battery. Here, I install a fuse across the diode, so that it adds to the safety of the charge circuit, as the fuse will blow if a short is made across the external wiring and then the standard diode backs up the protection.

SERVO GEARS

After a severe landing or crash the servos need to be checked for damage to their gear trains. It is not necessary to open up the case, as a real test is to rotate the servo output arm, without the servo being installed and driving the gear train back through its reduction to the motor. This very severe test will show up any weak or damaged gears by a ratcheting or even a freewheeling action. If you decide to replace the gears, make absolutely certain that you find and remove all the broken teeth, as they are sometimes the same color as the silicone grease used to quieting the gear action. Check for teeth stuck into the good gears and look where the motor pinion is located for more hidden parts. When you install the output gear, be very careful that you orient it in the correct direction to allow full circular travel looking at the position of the end stop molding.

TRANSMITTER ANTENNAS

The metal whip antennas take a beating, so you need to look them over regularly. Extend it fully and give it a shake, checking for slop in the sections, as this can be an intermittent connection. Clean it with tissue and alcohol and use WD40 as a lubricant. This will keep the internal connecting springs clean. If any of the sections slide back, replace the antenna, and never use metal gadgets to hold the flag in place. If you break the antenna, simply solder the pieces together with brass tubing while you wait for a replacement. Also check at the bottom as the threaded insert often breaks loose.

RECEIVER ANTENNAS

The standard length is one meter, while USA made receivers use three feet. However, the actual length is not that important, so don't panic if you chop off a few inches. You can safely splice back the broken end and cover the joint with heatshrink sleeving. To replace the antenna at the circuit board requires soldering skills, so it may be better to splice. Use a similar stranded wire, the gauge and insulation is not very important. Never string a antenna to the model using a metal clip at the end! Always try to route the antenna at least two inches clear of any other internal wiring.

Editors Note: Changing the receiver antenna length can and will adversely affect the range of the receiver.

TRANSMITTER DEAD?

You can check the operation of a 72 or 75 MHz transmitter by turning on a standard TV set to channel 3 or 4 and noting the pattern on the screen when the transmitter is close to it. You should hear a change in the buzzing sound as you move the sticks on a AM or FM, but not the PCM! A common cause for a dead transmitter is the internal fuse, which is sometimes well hidden. JR transmitters have a problem with weak spring metal in their fuse holders, which can be an annoying intermittent problem and needs retensioning when replacing the fuse.

The Futaba Attack and Conquest Transmitters often have intermittent on/off switches and the only way to replace them is complete dismantling of the stick assemblies and removing the front plate!

If you have a battery box for loose cells, this is deadly! Replace with soldered in cells, and in the Futaba 5 AU and 7 AU, these need their spring battery contacts removed and the connection replaced with suitable matched connectors.

Don't run you transmitter for longer than 15 minutes with the antenna collapsed, as this will, in time, damage the RF transistor due to excess heat build up. Use a servo driver to set up the servos, then use the transmitter to fine-tune the neutrals and travels. A low meter reading us usually a sign of a bad battery pack!

From Flightline, Jean Sellers, editor
13136 Surcease Mine Rd
Yankee Hill, CA 95965

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