Furuno FAR-21 7-BB Series, Operator'S Manual

Page: 242 / 305

6. MAINTENANCE, TROUBLESHOOTING
6-8
Advanced troubleshooting (con’t)
Problem Probable causes or check
points Remedy
Interference rejector is
inoperative (interference
rejection level not
displayed) SPU board Replace SPU board.
Echo stretch is ineffective
(neither ES1, ES2 nor ES3
is displayed) SPU board Replace SPU board.
Range rings are not
displayed 1) Adjust the brilliance of
range rings on the
BRILL menu to see if
intensity is increased
2) SPU board
1) Replace associated circuit board if
unsuccessful.
2) Replace SPU board.
Poor discrimination in
range Sea clutter control not
functioning properly Improper setting of A/C SEA. If A/C SEA
is seen only at very close range,
suspect inaccurate frequency of
reference oscillator.
True motion presentation
not working correctly 1) Poor contact of MODE
key (full keyboard)
2) Selection not accessed.
3) Speed entry incorrect
4) TM display inaccurate
1) Try to press MODE key a little
harder.
2) Press MODE key or operate
PRESENTATION MODE box until TM
appears.
3) Enter correct own ship speed
referring to paragraph 1.13.
4) Make sure that speed and compass
inputs are accurate.
Target not tracked
correctly Poor definition of targets in
sea clutter Adjust A/C SEA and A/C RAIN controls
referring to paragraph 1.17 and 1.18.
Buttons on trackball
module operated but no
response Trackball module Replace trackball module.