The main symptom for communication problems is the LCD on the RFU will read "waiting for communication" and is stuck on. There are 3 simple choices the end-user can take to fix this problem.
- Check the RFU configuration to see if "Multidrop" is off. If "Multidrop" is on, the RFU won't communicate with the console. To check the configuration, press and hold the top 3 buttons on the numbered portion of the RFU keypad upon boot up ("7, 8, 9" on the EXPN RFU2; "+, Thru, -" on the OBSN RFU2) . Cycle through each option with the "+" key and press the "1" key to change the "Multidrop" configuration. Press "Enter" when finished.
- The following should be done with the RFU unplugged from its' power source: Remove the 4 screws from the back panel and remove the back panel. Locate the main processor IC (U4). This IC sits in a socket. Sometimes, the IC and the socket create open connections between themselves, after inactivity over a long period of time. Usually, the IC needs slight readjusting. Pressing the IC firmly while rocking the IC back and forth inside the socket can fix this problem. It would be better to extract the IC with an IC extractor tool and reseat it back into the socket, if possible.
- Try swapping U2 and U3 with new 75176 driver ICs, if available.