Hi, Larry. I've had problems with relays in the TR-4 series transceivers as well as a latching relay at the base of my tower to switch between two feedlines. Any contact that doesn't carry sufficient current (think received signals) will over time develop a layer of corrosion. To "clean" the contact(s), a "wetting current" is required.
The TR7 has a direct path between the "ANT" (SO-239) connector and the "EXT RCVR" RCA connector on the back panel. Although I haven't had any trouble with my TR7, I did use the following procedure as a test: 1) Use a 12Vdc power supply (or a 9Vdc battery) with a series 470-Ohm/0.5W resistor to provide the wetting/cleaning current. The value of the resistor is not critical. 2) Connect one end of the resistor to the "ANT" connector center conductor and the other end of the resistor to the + lead of the power supply. 3) Ground the center of the "EXT RCVR" connector and connect the - lead of the power supply to the TR7 chassis. 4) Turn down the "MIC GAIN" and "CARRIER" controls to minimum settings (fully CCW). 5) Operate the PTT switch on the mic (set up the radio for voice operation) or operate the CW key (for CW operation) several times. 6) Disconnect the resistor and the short and test for proper RX operation. Repeat if necessary. If this procedure isn't successful, then a new relay is probably required. >From the schematics for the TR7, I don't see anything that could cause damage. >If anyone on the Drakelist knows better, pleas chime in! You could also remove the relay and use clip leads to make the various connections to the contacts and the coil of the relay. 73, Bob K9JU
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