CB Radio MAGNUM 257HP REPAIR TIP Update June 2010
While transmitting the radio "breaks lock" or the CPU malfunctions. Diagnoses,
1. Unsolder the shield of the coax that is connected to Output side of the RFX-75 where it connects at the radio.
2. Verify that there is continuity from the shield of the coax to the Chassis of the RFX-75. You may need to remove one of the screws holding the inspection plates on to the top or bottom of the RFX-75 and install one side of the ohm meter in the screw hole to get a good connection).
3. If there is no continuity, remove the two screws that attach the RFX-75 to the back of the radio to gain access to the component side of the RFX-75. Locate the screw shown in the picture below, and replace it with a zinc or nickel plated 3MM screw. This will make the connection needed from the Coax Shield to Chassis Ground