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No Sync Signal Jrc Radar -

The "No Sync Signal" error on a JRC radar typically indicates a critical communication failure between the display unit (processor) and the antenna (scanner unit). This message generally means the display unit is not receiving the necessary synchronization pulses—specifically the trigger or bearing signals—required to render the radar sweep on the screen. Common Causes of "No Sync Signal"

  • Quarterly:

    Part 2: Common Causes on JRC Radars

    Troubleshooting Methodology

    Resolving a "No Sync Signal" requires a methodical approach to avoid unnecessary parts replacement. The first step is a "heartbeat check": verifying if the antenna is rotating. If the antenna is stationary, the issue is likely a power failure or motor fault, not the sync circuit itself. Assuming the antenna rotates, the next step is utilizing built-in test equipment (BITE) or diagnostic software available on JRC units. However, the most definitive test is often a continuity check or voltage measurement. A marine electronics officer or technician will measure the voltage at the scanner unit output and compare it to the input at the display unit. If the signal exists at the source but not at the display, the cable is the fault. If the signal exists at the display input but the alarm persists, the display board is likely defective. no sync signal jrc radar

    • Locate the sync signal lines in the scanner cable shield (refer to your JRC manual’s interconnection diagram).
    • Measurement: Probe between SYNC+ and SYNC- (or SYNC and GND for single-ended).
    • Expected waveform: A 0-5V or ±2.5V differential pulse, 1–10 microseconds wide, occurring once per antenna revolution (plus a "heading marker" – a longer pulse at ship's heading).
    • What you may see:
      1. Loose / disconnected sync cable between antenna head and display unit.
      2. Failed slip-ring or brush assembly in antenna causing open/ intermittent sync contacts.
      3. Faulty sync generator or tachometer in antenna head.
      4. Damaged or corroded connectors, pins, or cable (moisture intrusion).
      5. Incorrect configuration or mode selection on the display (wrong antenna type or sync source).
      6. Power supply issues to antenna head (insufficient voltage, blown fuse).
      7. Faulty display unit input stage (sync input amplifier / isolator) or internal board failure.
      8. Interference from nearby electronics or grounding faults causing noisy/absent sync pulses.
      9. Firmware mismatch between antenna unit and display (less common).
      10. Failure of related sensors (gyro/heading encoder) when sync is combined with heading data — may present as sync/heading errors.
      • Blank or rolling PPI display, no rotating sweep.
      • Erratic bearing or range traces, or a frozen sweep.
      • Error message or alarm on console: “NO SYNC,” “SYNC LOSS,” or similar.
      • Radar transmitter may run (antenna rotates) without display sweep, or display shows timebase but no sync.

      No Sync Signal — JRC Radar: Causes, Diagnosis, and Fixes

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