Checking The Transducer - NorthStar Echo Sounder 491 Operation Manual

Configure the navigatorʼs
Aux Port for the 491. See
Section 1 of this manual
for instructions.
1. Check fuses and circuit
breakers.
2. Check power to 491 with
a voltmeter.
3. Verify that the data cable
between the navigator and
the 491 is properly wired
and connected.
The 491 and the navigator
aren't communicating properly.
Check the wiring of the data
cable between the navigator
and the 491.

Checking the transducer

491 Echo Sounder Operations Manual
No echoes displayed on sounder screen.
Is the
Advance
Speed set to
zero?
Has the
navigatorʼs
NO
Aux Port been
configured
for the
491?
Check
OFF
the 491's STAT
indicator
FLASHING
GREEN
Figure 10: Troubleshooting the echo sounder (957/958)
To provide the best possible performance with the 491 echo
sounder, Northstar recommends the use of an Airmar
YES Change the Advance Speed
setting.
NO
YES
491 is communicating with
the navigator.
1. Check transducer
STEADY
connector for the
GREEN
proper wiring.
2. If wiring is correct,check
transducer impedance
with an ohmmeter.
3. If the transducer is open
or shorted, replace it
RED
There's a hardware problem
with the 491.
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