1. Brief Summary: Troubleshooting document for diagnosing a fault with replacing the coax switch assembly on the 8897B, 9497B, 14400B, ST88, ST94 and ST144 antennas. 2. Checklist: Verify the Band of the Coax Switch Verify DC Voltage Switches the Coax Switch 3. Theory of Operation: The 8897B, 9497B, 14400B, ST88, ST94 and ST144 TVRO antennas feature a dual feed assembly supporting both C and KU band RF. A single quad linear KU band LNB is installed on the feed passing high horizontal, high vertical, low horizontal and low vertical RF paths through to the four channel rotary joint and in turn to the below decks distribution. Two separate C band LNB s are also installed on the feed assembly, one for horizontal polarization and one for vertical polarization. Both the low band KU RF paths are fed into the coax switch as are the C band horizontal and vertical paths meaning that the 4 channel rotary joint can be toggled between the 6 different RF paths depending on the required frequency range of the system. As default when the system initializes the C band RF will be selected, this means no voltage will be provided from the PCU to the coax switch assembly and ports J1 of the coax switches will be selected. Should KU band be selected from the tracking window of the DAC the PCU will output 12 15VDC to the coax switch assembly to select the J2 ports of the coax switched and in turn pass the low band KU RF paths to the rotary joint. 4. Troubleshooting the Coax Switch: Should the antenna not receive all of the KU band channels available then it s possible that the switch has failed and has defaulted to the C band channels. At this point the high band KU channels will still be received as there are fed directly into the rotary joint When KU band has been selected from the tracking window of the DAC it should be possible to measure 12 15VDC between pins 2 and 3 of the IDC connector on the coax switch assembly. If no voltage is present verify if the PCU/pol aux relay is outputting the voltage by measuring between the pins as stated on the below diagram for your model of antenna. If voltage is present but the coax switch has selected the C band RF paths the coax switch is defective and needs to be replaced. If no voltage can be measured on the IDC connector of the coax switch assembly or exiting the PCU/pol aux relay the PCU/pol aux relay isn t outputting the voltage, and needs to be replaced, if voltage can be measured on the PCU/pol aux relay but not on the IDC connector the harness is defective. Page 1 of 4
8879B, 9497B and 14400B ST88, ST94 and ST144 Page 2 of 4
5. Replacing the Coax Switch Assembly: 5.1. Tools. #1 Phillips Screwdriver 7/16 Wrench/Spanner Loctite 242 5.2. Procedure. Procedure for replacing the RF switch assembly, Sea Tel kit part number: 137335 (RF switch assembly part number: 128204 1). *Caution: Power down the pedestal before following this procedure. 1. Using a #1 Phillips screwdriver remove the screw securing the coax switch connection of the reflector harness from the termination block. 2. Disconnect the coax switch IDC connector from the termination block. 3. Now disconnect the two RG 179 coax cables from the in output side of the coax switches using a 7/16 wrench. 4. Now disconnect the four RG 60 coax cables from the input side of the coax switches using a 7/16 wrench. Page 3 of 4
5. With all the cables removed from the coax switch remove the 4 screws securing the switch to the PCU assembly using a #1 Phillips screwdriver. Save the hardware for future use. 6. Install the replacement coax switch to the PCU assembly using the hardware removed in step 5 ensuring the P clips are installed on the lower screws. Apply Loctite 242 to the threads. 7. Reconnect the white and blue RG 179 coax cables to the coax switches as per the labels on the mounting plate. 8. Reconnect the four RG 60 coax cables to the coax switches matching the colors to the labels on the mounting plate. 9. Reconnect the IDC connector to the termination block on the PCB. 10. Secure the grounding point to the screw securing the termination PCB using a #1 Phillips screwdriver. Apply Loctite 242 to the thread. Page 4 of 4