2.6 Troubleshooting Information
If error indications are displayed on the 500W series unit, consult the Troubleshooting section contained
below:
Problem
The 500W Series
unit does not power
on.
The 500W Series
unit does not
compute a position.
GPS signal levels
drop when avionics
are turned on.
The GPS signal
levels are very low.
The 500W Series
unit does not
transmit.
The sidetone level is
too low or too high.
OBS Resolver won't
calibrate.
500W Series
Instructions for Continued Airworthiness Bell 206B
Table 2 Troubleshooting Guide
Possible Cause
The unit is not getting power to
the main connector P5001.
Not receiving signals.
Noise interference from other
avionics.
Improper antenna installation or
coax routing.
Antenna shaded from satellites.
RF interference at 1575.42
MHz from VHF COM.
The PTT input is not being
pulled low.
No transmit power to the COM.
The input voltage is too low.
Wrong type of headsets, or
level needs adjustment.
Incompatible resolver or
improper connection.
Solution
Make sure power is connected to the
main 78-pin connector P5001, pins
19 and 20 and ground to P5001, pins
77 and 78. Check circuit breakers
and main avionics switch.
Check the GPS antenna connections.
Make sure the aircraft is clear of
hangars, buildings, trees, etc.
Wait 20 minutes for unit to complete
cycle.
Turn all avionics off, then turn on
each piece one at a time to isolate
the source of the interference. Route
GPS cable and locate GPS antenna
away from sources of interference.
Check GPS antenna installation,
connections, and cable routing. The
GPS antenna must be mounted on
the top of the aircraft.
Make sure the aircraft is clear of
hangars, buildings, trees, etc.
Move GPS antenna further from the
COM antenna. Add a 1575.42 MHz
notch filter in COM coax. Fix or
replace the COM. Disconnect the
ELT antenna coax to check for
possible re-radiation.
Check that the PTT (mic key) input is
pulled low for transmit.
Make sure power input is connected
to the COM 25-pin connector P5002
11 and 12 and ground to P5002 21
and 22.
Increase input supply voltage to
>12VDC. (>24VDC for 530AW
models)
If necessary, adjust the sidetone
level. Sidetone adjustment is found
on the COM Setup page.
Check the resolver specifications and
wiring.
190-01226-03 Rev. 5
Page 11 of 23
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