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3-6 190-00067-25 Rev D
3.5 TROUBLESHOOTING
Table 3-2 contains problem/action information to aid in troubleshooting the GPS 155XL Perform the actions in
the sequence they are listed.
Table 3-2. Troubleshooting Chart
PROBLEM ACTION
Unit will not power on Check External Power Connection
Check Remote External Battery Pack (if equipped)
Check Power Switch
Replace Power Switch (see section 4.3.7)
Replace CPU Board (see section 4.3.5)
Unit will not power off Replace CPU Board (see section 4.3.5)
Replace Power Switch (see section 4.3.7)
Display has horizontal or vertical lines Replace Display Module (see section 4.3.9)
Replace CPU Board (see section 4.3.5)
Display has missing or dark pixels Replace Display Module (see section 4.3.9)
Display brightness not adjustable
manually
Replace CPU Board (see section 4.3.5)
Replace Control/Display Unit (see section 4.3.2)
Display brightness not adjustable via
photocell
Replace Control/Display Unit (see section 4.3.2)
Replace CPU Board (see section 4.3.5)
Keycaps have no backlighting Replace Control/Display Unit (see section 4.3.2)
Replace CPU Board (see section 4.3.5)
Keycap backlighting not uniform Replace Control/Display Unit (see section 4.3.2)
Bezel Annunciators do not function Replace Control/Display Unit (see section 4.3.2)
Replace CPU Board (see section 4.3.5)
No external annunciator output(s)
(message, arrival)
Check connections and verify operation in Test
Mode
Replace CPU Board (see section 4.3.5)
Keycaps do not function properly Replace Control/Display Unit (see section 4.3.2)
Replace CPU Board (see section 4.3.5)
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 4.3.8)
Replace Display Module (see section 4.3.9)
Replace CPU Board (see section 4.3.5)