TM   55-1520-240-T 1-1   FAILURE   SYMPTOM   LIST   (CONTINUED) 1-1 SYMPTOM TASK SYMPTOM TASK DOPPLER/GPS   NAVIGATION   SYSTEM   (DGNS) EDGE  LIT  PANEL  DOES  NOT  LIGHT  OR  VARY CDU MAL LAMP AND ALL LED SEGMENTS ARE NOT ILLUMINATED CDU DISPLAY NOT GO ALL GPS ALERT INDICATOR DOES NOT ILLUMINATE PRESENT  POSITION  NOT  DISPLAYED  ON  CDU CDU DOES NOT DISPLAY DOWNLOAD WAYPTS DURING    WAYPOINT    LOADING INDICATIONS   ON   THE   FOUR-LINE   DISPLAY AND HSI ARE NOT THE SAME GPS  DOES  NOT  ZEROIZE GPS HAVEQUICK TIMING NOT WORKING HF  LIAISON  FACILITY AN/ARC-220 CONTROL-DISPLAY SCREEN INTENSITY LEVEL DOES NOT VARY WITH BRIGHTNESS    SWITCHES AN/ARC-220  CONTROL-NO  DISPLAY  VISIBLE TSEC/KY-100 CONTROL RCU-NO DISPLAY AN/ARC-220  CONTROL-DISPLAYS  "SYSTEM- NOGO"  AFTER  POWER  -UP  BIT  (P-BIT)  TEST AN/ARC-220  CONTROL-DISPLAYS  "SYSTEM- NOGO RT-CDU COMM FAIL” DURING RCV OR XMT BIT AN/ARC-220   CONTROL-DISPLAYS   “LOAD-FAIL” DURING DATA/KEY FILL AN/ARC-220 RECEIVER-TRANSMITTER - RECEPTION/TRANSMISSION   NOT   CLEAR   OR MISSING IN ALL MODES HF  LIAISON  FACILITY-“CALL  FAIL”  DISPLAYED WHEN PLACING ALE OR ECCM CALL HF LIAISON FACILITY-SYSTEM CANNOT BE TUNED   OR   SYNCHED   DURING   ECCM   OPERATION HF LIAISON FACILITY-PREAMBLE TONES NOT HEARD WHEN PLACING A CALL IN ECCM MODE 18-3.4 18-3.5 18-3.6 18-3.7 18-3.8 18-3.9 18-3.10 18-3.11 18-3.12 18-4.4 18-4.5 18-4.6 18-4.7 18-4.8 18-4.9 18-4.10 18-4.11 18-4.12 18-4.13 HF  LIAISON  FACILITY-“LINKED”  IS  NOT DISPLAYED   ON   HF   CONTROL   WHEN   PLACING ALE OR ECCM CALL HF LIAISON FACILITY-HEADSET AUDIO IS NOT RESTORED   AFTER   LINK   ESTABLISHED   WHEN PLACING ALE OR ECCM CALL HF LIAISON FACILITY-” RCVING PREAMBLE” NOT DISPLAYED  BEFORE  AN  ECCM  CALL  IS  RECEIVED HF    LIAISON    FACILITY-PREPROGRAMMED INFORMATION   CANNOT   BE   ZEROED TSEC/KY 100 CONTROL RCU CANNOT KEY FILL FROM  KEY  FILL  DEVICE TSEC/KY-100 CONTROL RCU-KEYS CANNOT BE ZEROED SECURE VOICE OPERATION - WITH KY-100 CONTROL SET TO CT MODE AND PLAINTEXT TRANSMITTED   TO   RADIO   UNDER   TEST, COMMUNICATION  NOT  HEARD SECURE  VOICE  OPERATION  -  WITH  KY-100 CONTROL  SET  TO  VARIOUS  POSITIONS  AND BOTH CIPHERTEXT AND PLAINTEXT TRANSMITTED   TO   RADIO   UNDER   TEST ABNORMAL COMMUNICATIONS AND ANNUNCIATOR   OCCUR 18-4.14 18-4.15 18-4.16 18-4.17 18-4.18 18-4.19 18-4.20 18-4.21 Change   16 1-16A/(1-16B  Blank)