No Sync Signal Jrc Radar Hot! -

Troubleshooting the "No Sync Signal" Error on JRC Radars Encountering a "No Sync Signal" 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.

This guide explores the common causes and provides a step-by-step troubleshooting path for JRC series like the JMA-5300, JMA-2300, and JMA-9100. 1. Identify the Missing Signal Components

A JRC radar relies on several pulses to create a synchronized image. If any of these are lost, the "No Sync" error may trigger:

Transmitting Trigger: An 8Vp-p signal that tells the display when a pulse is sent.

Rotation Pulses (Azimuth): Typically 2048 pulses per revolution, telling the display where the antenna is pointing.

Bearing Signal (Heading Pulse): A single pulse per revolution to align the image with the ship's bow. 2. Immediate Physical Checks no sync signal jrc radar

Before diving into circuitry, perform these basic inspections:

Verify Antenna Rotation: Ensure the radar pedestal is receiving the correct voltage. If the motor isn't spinning, the system cannot generate azimuth or heading pulses.

Inspect Interunit Cabling: Check for signs of corrosion on the pins of the interunit cable connectors. Flexing over time can crack internal wires.

Power Supply Stability: Low battery voltage or a tripped breaker can lead to intermittent sync issues. 3. Advanced Troubleshooting Steps Step 1: Check the Scanner Power and Safety Switch

If the scanner unit lacks sufficient power, it cannot generate the necessary trigger signals. Troubleshooting the "No Sync Signal" Error on JRC

Safety Switch: For models like the JMA-9100, check if safety switch S101 in the scanner unit is off, as this prevents transmission.

Voltage Test: Verify the processor is outputting the required DC voltage (typically between +10.2V and +42V for smaller units) to the scanner. Step 2: Test the Pulse and Encoder Boards

If the antenna is rotating but the "No Sync" error persists, the problem likely lies in the signal generation:

Faulty Encoder: A malfunctioning encoder fails to send the 2048 pulses per revolution required for azimuth data.

Modulator/Control Board: Inspect the modulator circuit board (e.g., Cpa-264 in some models) for damage or loose cable connections. Step 3: Receiver and Tuning Adjustments 2. The Display Processor (Radar Unit)

Sometimes, a "No Sync" or "No Signal" message is related to a weak receiver state: JRC Radar TXRX(AZI) Troubleshooting Guide | PDF - Scribd

3.2 Scanner Unit Internal Fault

Fix:

Part 3: Immediate Field Diagnostics (Step-by-Step)

Safety First: Turn off the radar and lock out the breaker. Magnetron capacitors hold lethal voltage for minutes.

5. Incorrect Antenna Rotation Speed Setting

Modern JRC radars allow you to set rotation speed (24, 36, 48 RPM) via software. If the scanner is physically rotating at 24 RPM but the display is set to SCAN SPEED: 48 RPM, the sync timing will be rejected as invalid, triggering the alarm.

Primary Causes of "No Sync Signal" on JRC Radars

Based on field service data and JRC technical manuals, the fault can be traced to three main areas.

1. Faulty Scanner Cable or Connectors (90% of cases)

The multi-conductor cable between the display and the scanner carries power, trigger, video, and sync. Over time (5–15 years), corrosion, moisture ingress, or broken strands in the sync pair cause intermittent or total loss.

2. The Display Processor (Radar Unit)