Furuno GP-90 Service Manual page 21

Symptom: No key response
Flow 5
Power-up Self test?
OK
Single key is
defective?
No
All Keys?
Yes
Defective NP Board
Sig.
KR0
KR1
KR2
KR3
KR4
NG
Yes
Table 4.6 Key matrix
KS3 KS2
PLOT
+/!
ON/OFF
GOTO CLEAR
WPT
TONE
RTE
MARK CENTER
18
Defective NP Board
Defective key switch on PNL Board
Check keys for row and column wirings,
using the key matrix below, U20 on NP
Board is defective, if wiring is okay.
KS1
EVENT
MOB
NU/CU
ENT
MENU
ESC
DISPLAY
SEL
4. Troubleshooting
KS0