VisionMaster Ship’s Manual Chapter 7
Fault Reporting and First Line Servicing Fault Identification and Isolation
65900011 7–7
2 Fault Identification and Isolation
2.1 VisionMaster FT System Fundamentals
To help simplify the diagnosis of system faults, the following paragraphs
describe some fundamental characteristics of the VisionMaster FT units.
2.1.1 Power Supply Start-up
For the Power Supply to operate the DU Data+ and DU Data- signal lines
must be active. It is not necessary for serial data to be present: a DC voltage
>2.5V between the lines will start the Power supply.
Note: A test link LKA on Power Supply PCBs can be set to position 1–2 to
make the Power Supply operate independently of the DU Data input.
This link must only be used in this position as a service aid. It must
be reset to position 2–3 for normal operation otherwise the PCIO will
not be able to switch the Transceiver on or off.
2.1.2 Azimuth and Comms
There are four separate signals between the PCIO unit and the Transceiver:
• serial control messages from the PCIO;
•video;
• RS422 trigger; and
• serial tellback messages from the Transceiver.
The tellback messages are a serial message stream. They contain the
azimuth, heading marker information, BIST and status tellback bits. The
messages are made up of a number of characters.
WARNING! – Lethal Voltage Hazard
Lethal voltages are exposed when the covers are removed from the
units.Only qualified persons should work on the equipment when
power is applied. ALWAYS isolate the unit from the mains supply
when removing or replacing the cover. To make the units safe it is
necessary to isolate them from the mains supply. It is not adequate
to turn the unit off: there are high voltages present at any Power
Supply that is not mains isolated.
WARNING! – Lethal Voltage Hazard
Once mains is applied to the PSU board in the Transceiver, high-
voltage DC is present on all primary power components. This voltage
is present even when the unit is switched off. The high voltage is only
removed if the unit is isolated from the mains supply.
To Next Page
