TM  11-5820-890-20-2 4-1 CHAPTER 4 CONTROL, RECEIVER TRANSMITTER (RCU) (C 11561) Subject Para Page Operational Check 4.1 4-1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . Troubleshooting Flowcharts 4.2 4-5 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4.1. OPERATIONAL CHECK. General guidelines for checking problems in the Control, Receiver Transmitter (C 11561), commonly referred to as the remote control unit or RCU, are as follows. In that the RCU is always used in conjunction with some version of the SINCGARS radio, an important first step is to isolate the problem between the RCU and the radio as early as possible. If a vehicular radio is used with the RCU being checked, it may be necessary to troubleshoot a VIC or Single Radio Mount (SRM), as covered in other chapters of this manual. Once the problem is isolated, make use of the appropriate radio troubleshooting procedure or the one for the RCU which follows. As in troubleshooting a radio, the RCU Operational Check is the start point. It will identify the faulty component or direct you to a specific Troubleshooting Chart to use. Once replacement or repair has been completed, it is important that you again perform the Operational Check to ensure full operability. If feasible, RCU and radio should be at the same location for troubleshooting. If co location cannot be achieved, troubleshooting requires two personnel. OPERATIONAL CHECK FOR RCU STEP 1.    PREPARATION: STEPS TO PERFORM CHECKS TO MAKE ACTIONS TO TAKE 1.1 Perform Operational Check on radio system If Manpack Radio, see TM 20-1 Chapter 2 PASS:  Go to Step 1.2 FAIL:    Troubleshoot manpack radio If Vehicular Radio, see TM 20-1 Chapter 3 PASS:  Go to Step 1.2 FAIL:    Troubleshoot vehicular radio If Single Radio Mount, see this TM  Chapter 5 PASS:  Go to Step 1.2 FAIL:    Troubleshoot SRM 1.2 Set RCU: FCTN to STBY CHAN to MAN MODE to SC RF PWR to HI VOL to Mid Range DIM to Full CW COMSEC to CT SPEAKER to OFF N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A N/A 1.3 Handset (HS), H250: Connect to RCU AUD/DATA Ensure HS  is operational Install known good HS 1.4 Main battery * Ensure good power Install known good battery, if required 1.5 Hold Up Battery (HUB) Ensure good HUB Install known good HUB, if required *  If RCU is vehicular mounted perform STEP 6 at this time and return to STEP 1.5.