SPERRY MARINE 03956 885378-2 DEMODULATOR DUAL CHANNEL

The Sperry Marine 03956 885378-2 (often fully cataloged as 03956-1885378-2) is a Dual Channel Demodulator PCB. It is a critical component used in marine navigation systems, most notably within the VisionMaster FT Radar and older Sperry Gyrocompass or Autopilot systems.

Following your previous queries, this board is the “bridge” between raw analog sensor data (like from a radar transceiver or a gyro) and the digital computer systems you’ve been asking about.

Core Technical Function

A “Demodulator” in a marine context typically takes a high-frequency carrier signal and extracts the underlying data. This specific board is designed to handle:

• Dual Channel Processing: It can simultaneously process signals from two independent sources (e.g., two different radar transceivers or two different sensor inputs).

• Signal Conversion: It converts AC signals (often 400 Hz or 60 Hz, common in marine power/gyro systems) into a format that the system’s CPU (like the JK-CPU we discussed) can interpret.

• Synchronization: It helps synchronize the radar “trigger” or gyro heading with the display unit so the image/data appears correctly on the bridge screen.

Specifications & Context

• Part Number: 03956-1885378-2 (also listed as 885378-2).

• Manufacturer: Sperry Marine (Northrop Grumman).

• Common Operating Frequency: Rated for 60 Hz or 400 Hz signals.

• System Integration: It is part of the VisionMaster FT architecture, which allows a single bridge screen to overlay data from two separate radar sensors (Dual Channel Radar) to eliminate “blind arcs.”

Why this board is in your system

Since you’ve been asking about JK-TONE, JK-CPU, and ABB boards, you are likely working on a Integrated Bridge System (IBS) or a Marine Communication/Navigation Rack.

• The JK-series boards handle the internal phones and communication.

• The ABB RQBA handles power redundancy.

• The Sperry 885378-2 handles the navigation sensor data (Radar/Gyro).

Troubleshooting Tips

If your radar or gyro data is missing or “noisy” on the display, but the computer itself is running:

1. Check the 400Hz/60Hz Input: Use an oscilloscope or a high-frequency multimeter to ensure the carrier signal is reaching the board.

2. Calibration: These boards often have small potentiometers (trimmer resistors). If the gyro heading is slightly “off” or the radar image is skewed, these may need adjustment—though this should usually only be done with a service manual.

3. Surplus Market: This board is officially “Discontinued by Manufacturer.” Like the other boards you’ve mentioned, it is mostly available via industrial surplus vendors (often found in the Bhavnagar/Alang ship-breaking region).