Furuno FAR-2107 Operator's Manual page 253

Problem
Interference rejector is
inoperative (interference
rejection level not
displayed)
Echo stretch is ineffective
(neither ES1, ES2 nor ES3
is displayed)
Range rings are not
displayed
Poor discrimination in
range
True motion presentation
not working correctly
Target not tracked
correctly
Buttons on trackball
module operated but no
response
Picture is not updated with
each sweep.
Advanced troubleshooting (con't)
Probable causes or check
points
SPU board
SPU board
1) Adjust the brilliance of
range rings on the
BRILL menu to see if
intensity is increased
2) SPU board
Sea clutter control not
functioning properly
1) Poor contact of MODE
key (full keyboard)
2) Selection not accessed.
3) Speed entry incorrect
4) TM display inaccurate
Poor definition of targets in
sea clutter
Trackball module
1) Slots in rotating disc in
antenna unit
2) Motor brushes
6. MAINTENANCE, TROUBLESHOOTING
Remedy
Replace SPU board.
Replace SPU board.
1) Replace associated circuit board if
unsuccessful.
2) Replace SPU board.
Improper setting of A/C SEA. If A/C SEA
is seen only at very close range,
suspect inaccurate frequency of
reference oscillator.
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 section 1.13.
4) Make sure that speed and compass
inputs are accurate.
Adjust A/C SEA and A/C RAIN controls
referring to section 1.17 and 1.18.
Replace trackball module.
1) Remove foreign material (carbon,
grease, etc.) from slots.
2) Replace motor brushes if they are
shorter than 6 - 7 mm.
6-9