Installation manual

222 | Simrad MX500
from white to black. Highlight OK then press ENT if it
varies correctly or Fail if it doesn’t. Next, the CDU will
conduct a Backlight test. Observe that the display goes
through its full range of illumination. Highlight OK then
press ENT if it varies correctly or Fail if it doesn’t.
Then, the CDU will conduct a Keylight test. You may need
to dim the lights in the room or shade the keyboard so
that you can see the backlights behind the function and
softkeys. Observe that the keypad backlights go through
their full range of illumination. Highlight OK then press
ENT if it varies correctly or Fail if it doesn’t. Next, the
CDU will conduct a Beeper test. Listen that the internal
beeper activates for about a second. Highlight OK then
press ENT if it varies correctly or Fail if it doesn’t. Finally,
the CDU will conduct an External Alarm test. Listen that
the external alarm activates continuously. Highlight OK
then press ENT if it varies correctly or Fail if it doesn’t.
Upon completion of the above tests, a Test Results
screen will be displayed. In addition to the visual tests
which you witnessed, the CDU also performs background
tests on the program memory (FLASH ROM), the real-
time Clock, and the Serial (NMEA) Ports. These tests
check about 90% of the CDU. The items which it does not
check are the GPS and Beacon receivers in the antenna.
If one of the background tests fail, you can try clear-
ing the CDU’s memory to see if the problem will clear.