Humminbird Platinum ID 120 Operation Manual page 33

MAINTENANCE AND WARRANTY
TROUBLESHOOTING
5. The unit comes on before I press POWER, and won't turn off.
Check the transducer cable. If the outer jacket of the cable has been cut and the cable
is in contact with bare metal, you need to repair the cut with electrical tape. If there is no
problem with the cable, disconnect the transducer from the unit and see if the problem
is corrected, to confirm the source of the problem.
6. I get gaps in the reading at high speeds.
Your transducer needs adjusting. If the transducer is transom-mounted, there are two
adjustments available to you - height and running angle. Make small adjustments and
run the boat at high speeds to determine the effect. It may take several tries to optimize
high speed operation. This can also be a result of air or turbulence in the transducer
location caused by rivets, ribs, etc.
7. My unit loses power at high speeds.
Most Humminbird fishfinders have over-voltage protection that turns the unit off when
input voltage exceeds 20 VDC. Some outboard motors do not effectively regulate the
power output of the engine's alternator and can produce voltage in excess of 20 volts
when running at high RPMs. Your fishfinder displays input voltage in the Diagnostic
screen. Use this readout to determine if the voltage exceeds 20 VDC.
8. The screen begins to fadeout. Images are not as sharp as normal.
Check the input voltage using Diagnostic. The fishfinder will not operate on input
voltages below 10 VDC.
9. The display shows many black dots at high speeds and high sensitivity
settings.
You are seeing noise or interference caused by one of several sources. Noise can be
caused by other electronic devices. Turn off any nearby electronics and see if the
problem goes away. Noise can also be caused by the engine. If engine noise is causing
the interference, the problem will intensify at higher RPMs. Increase the engine speed
with the boat stationary to isolate this cause. Propeller cavitation can appear as noise
on-screen. If the transducer is mounted too close to the propeller, the turbulence
generated can interfere with the sonar signal. Ensure that the transducer is mounted at
least 15" (38cm) from the prop.