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Written by: Mark Gilger, WB0IQK
If your TR-3, TR-4 series, or T4X series antenna relay has problems, the first place to start is to perform a proper cleaning. This is best performed with one or both of the following processes. This procedure also can be applied to the carrier oscillator K2.
Minor problems can be corrected by putting a small drop of DeoxIT D5 contact cleaner on a small strip of card stock. Cut a piece to approximately 1/8th inch wide, and several inches long. Make sure the power has been removed from the unit. Slip the card stock in-between one side of each of the contacts and slip it back and forth a few times. Operate the contacts by hand to enable you to slip the card stock in place and provide pressure on the contact as you move it around. If the card stock is dirty when removed, replace it with new stock and repeat procedure. Once the card stock can be removed without being dirty, it now is time to move to other side of the relay contacts. The top side, contact farthest away from the coil assembly, will require you to carefully push each relay contact away from the contact to slip the card stock between the contacts. Repeat the procedure used. In most cases, this procedure should solve your problems. DeoxIT can be obtained from: Antique electronic supply, 6221 S. Maple Ave, Tempe, AZ 85283, Phone 800-706-6789, E-mail: email@example.com, Part Number: S-CD5S-6, http://www.tubesandmore.com
For the stubborn jobs, where the contacts contain a large amount of oxidation, a Burnishing Tool similar to the one shown here will be needed. Put the tool between the contacts, and operate the relay by hand to provide pressure on the contact while you move the burnishing tool in and out (like a file). Perform this operation on both sides of the contact. The burnishing tool has a very, very fine abrasive on it, so it only removes oxidation, not the metal.
This tool can be obtained from:
In place of a Burnishing tool, you can utilize s small strip of 1000 or 1500 grit wet dry sand paper. Fold the strip over, so the grit side is facing outward on both sides. Slip the strip in between the contact and move the strip back and forth. With the strip folded over, you will be doing both contacts at once.
The TR-4C and T4XC relays are more reliable than the earlier model, referenced above, the above procedure can be used. Removal of the plastic cover can be a pain, but with care, its possible by using of a very small bladed screw driver to pry the cover off. Since the relay can be removed from the radio, the actual cleaning process is easier to perform than the earlier models.