"No Sync Signal"
Troubleshooting the "No Sync Signal" Error on JRC Radars Encountering a message on your JRC (Japan Radio Co.) radar display is a critical alert that indicates a breakdown in communication between the processor/display unit and the scanner (antenna) unit. Without this synchronization signal, the radar cannot determine the timing required to sweep the display, resulting in a blank screen or a frozen image.
Diagnosis:
Technician used a USB oscilloscope to log the sync line for 1 hour. The log revealed a 200ms dropout every 697 seconds (coinciding with the air conditioning compressor cycling on the bridge).
Physical Connections
: Loose or corroded pins in the multi-core cable connecting the antenna to the display unit.
- Regularly inspect and clean slip rings/brushes, seal cable glands, verify connector integrity, verify firmware updates, and exercise antenna rotation to prevent moisture buildup.
How to Temporarily Bypass "No Sync" (Emergency Navigation Only)
Without sync:
The screen may be blank, show random noise, a frozen picture, or a “NO SYNC SIGNAL” alarm.
- "No sync signal" on a JRC (Japan Radio Company) marine radar indicates the radar display is not receiving the expected synchronization pulses from the radar scanner (antenna/head). That prevents the PPI display from drawing correctly or at all. This write-up covers likely causes, diagnostic checks, and remedial actions — organized from simplest/quick checks to deeper electrical and system-level troubleshooting.
The "No Sync Signal" error on a JRC radar is a technical roadblock, but not a dead end. In 70% of cases, the fault lies in the azimuth encoder or the rotary joint. In 25% of cases, it is a cable or connector issue. Only 5% involves major board-level failure.
- Locate the Sync output pins on the JRC terminal block (Refer to JRC maintenance manual—typically pins 3 & 4 on CN-1).
- Probe between Sync+ and Sync-.