Furuno GP-90 Service Manual page 19

Symptom: No DGPS 2D/3D mode
Flow 3
"BEACON RCVR
INSTALLED" appears
at power - up display
Yes
Selftest is OK?
(Menu, 8,1)
Beacon OK
Station selection and
initialization are OK?
Yes
Receiving Condition?
(Menu, 7)
Signal strength: 30 dB, SN ratio: less than 7 dB
Station ID is OK?
(Menu, 7)
Number displayed
DGPS Data is OK?
(Menu, 7)
Good
Beacon Station is normal?
(Menu, 7)
Normal
Defective GN-8091
No
Beacon NG
No
Signal strength and S/N
ratio: 1 to 4 dB
Blank
"- -" or abnormal
Abnormal
16
4. Troubleshooting
Defective U16
(Beacon receiver is detected automatically)
Defective cable between beacon receiver and
NP Board, or defective NP Board
Select an adequate station and initialize
correctly
Defective beacon antenna or defective
beacon receiver
Out of beacon signal coverage area, or poor
grounding of beacon antenna
Far from beacon transmitter, or poor
grounding of beacon antenna
Beacon transmitter problem