14
2.4
TROUBLESHOOTING CHART
MESSAGE
RECOMMENDED REPAIR
Unit will not power on
Check External Power Connection
Check Remote External Battery Pack (if equipped)
Check Pwr/Volume Switch Connection
Replace Pwr/Volume Switch (see Section 3.2.7)
Replace CPU Board (see Section 3.2.4)
Unit will not power off
Replace CPU Board (see Section 3.2.4)
Replace Pwr/Volume Switch (see Section 3.2.6)
Display has horizontal
or vertical lines
Replace Display Board (see Section 3.2.8)
Replace CPU Board (see Section 3.2.4)
Display has missing or
dark pixels
Replace Display Board (see Section 3.2.8)
Display brightness not
adjustable manually
Replace CPU Board (see Section 3.2.4)
Replace Control/Display Unit (see Section 3.2.1)
Display brightness not
adjustable via photocell
Replace Control/Display Unit (see Section 3.2.1)
Replace CPU Board (see Section 3.2.4)
Keycaps have no
backlighting
Replace Control/Display Unit (see Section 3.2.1)
Replace CPU Board (see Section 3.2.4)
Keycap backlighting not
uniform
Replace Control/Display Unit (see Section 3.2.1)
Bezel Annunciators do
not function
Replace Display/Control Unit (see Section 3.2.1)
Replace CPU Board (see Section 3.2.4)
No external annunciator
output(s) (message,
arrival, approach)
Check connections and verify operation in Test Mode
(see Section 4.2.3)
Replace CPU Board (see Section 3.2.4)
Keycaps do not function
properly
Replace Control/Display Unit (see Section 3.2.1)
Replace CPU Board (see Section 3.2.4)
Dual concentric (rotary)
knobs do not function
properly
Check Flex Circuit connection from rotary switch to
back of Control/Display Unit
Replace Rotary Switch Assembly (see Section 3.2.7)
Replace Display Board (see Section 3.2.8)
Replace CPU Board (see Section 3.2.4)
Approach arm switch not
functioning properly
(300 only)
Check connections and verify operation in Test Mode
(see Section 4.2.3)
Replace external switch
Replace CPU Board (see Section 3.2.4)
Sequence Hold low
switch not functioning
properly (300 Only)
Check connections and verify operation in Test Mode
(See Section 4.2.3)
Replace external switch
Replace Comm Chassis Sub Assy (see Section 3.2.2,
steps 1-7)
Replace CPU Board (see Section 3.2.4)
GPS reception weak or
GPS Status Page shows
low signal levels
Replace Antenna and/or antenna cable
Replace GPS Receiver Board (see Section 3.2.5)
