5.21 ELECTRICAL (continued)
Problem: A random static noise comes through the headset.
Solution: Adjust the volume and squelch on the intercom and determine if this will make the noise disappear. If the noise can be
controlled with the intercom volume and squelch it means that most likely the noise is being generated by the headset microphone,
mic jack, mic hi or mic lo wires. Unplug the headset. If the noise goes away try a different headset. If the noise still persists remove
each mic pin from the wiring harness one location at a time and see if the noise goes away (checking the wires connected to the
headset jack, wires connecting the headset jacks to the control module and the wires connecting the control module to the
intercom). Check that d-sub pins and solder joints all make a proper connection and do not generate the noise when the wires are
wiggled.
If the noise is not affected by the volume and squelch turn off your radio. If the noise goes away the sound is being generated by
your COM. One of the most common issues is the COM receive squelch being broken. A COM radio has an internal squelch setting
to control what level of input from the COM antenna will open the COM squelch, similar to how the squelch level is set for the mic
on a headset using the squelch knob on an intercom. If set too low, bursts of noise picked up by the antenna may break the
squelch. Consult the user manual supplied with your COM radio and turn the receive squelch up slowly until the noise disappears.
Note setting the receive squelch too high will prevent your radio from receiving faint transmissions and therefore great care should
be taken to set the squelch as low as possible while still eliminating any noise. Conduct this test outside and away from the source
of any electronic signals that may be picked up on the antenna.
If the noise is not affected by the squelch or the radio, try the troubleshooting steps listed for a rhythmic noise.
If the problem still persists disconnect the mono and stereo inputs from the back of the intercom one at a time and determine if the
noise goes away. This may help isolate where the noise is coming from.
Turn the audio level pots up or down in the control module. If the sound level of the noise problem changes the problem is between
the device generating the audio and the control module. If the sound level does not change the problem is between the control
module and the intercom, in the intercom or between the headset and the intercom.
If turning off a device removes the noise from the system check that the unit is properly grounded. First remove any wires that are
dedicated to audio ground and run the device off its own primary ground. If this does not change the noise run an extra wire from
the case of the device to the structure of the aircraft. If the noise still persists consider using a ground loop isolator (GLI) on the
wires coming from the device.
When troubleshooting a stereo music input, first disconnect the ground from the music lo or music ground input. Noise coming into
an audio system may be transmitted through ground connections to the audio system and most often the music ground/lo. By
removing the music lo connection the music will have no connection to ground and the lo will be become a “floating ground”. Use an
aux music device to determine if the music input is still useable. Since the ground is floating possibly higher, the magnitude of the
signal will be smaller. A signal with less amplitude will result in less volume.
PAGE
REVISION:
DATE:
VAN'S AIRCRAFT, INC.
09/24/13
1
RV-ALL
05-27
Problem: My EFIS warning tones are too quiet I can't change the sound levels using the audio mixer on the control module.
Solution: Check that your headsets are turned to stereo not mono mode. On some headsets this may be a small and hard to find
switch see the manual that came with your headset to be absolutely sure you have the headset in stereo mode.
Problem: My EFIS is generating a high level of background noise when turned on.
Solution: See the troubleshooting section on a random noise comes through the headset.
Problem: Strobe noise in the headset.
Solution: There are multiple ways the strobe noise will enter the audio system. Try turning the COM radio off and see if the noise
goes away. Is the noise only present while the radio squelch is open during receive or transmit? If so the noise is a high frequency
RFI noise being picked up on the radio com antenna (some strobes use circuitry in this band, most light manufacturers are now
aware of this and have changed their products to remove this issue). Add a choke (magnet that goes around a wire) around the
wires coming from each strobe device. Add the choke as close to the device as practical. If all the wires will not go through the
choke make sure to at least capture the power and ground wires.
Try also adding a capacitor to the power line. The larger the capacitor the more effective but at some point the inrush current
(current filling the capacitor when the circuit is turned on) will blow the fuse on that circuit.
If the above options have not resolved the problem, try shielding the wires for nav/strobe if they have not been shielded already. If
the noise is coming in on the mic line (volume of the noise increases when the intercom volume increases with the intercom squelch
broken as would be the case if you were talking through the intercom) inspect how your mic line is configured. If the shield for the
mic wire is used to provide the mic lo any noise picked up by the shield will be transmitted into the audio system. Older Van's kits
were wired this way and in many cases there have been no problems. If this is deemed to be a problem replace the mic wire with a
multi-conductor wire that will allow the mic ground to be a separate wire within the shielded bundle.
Dimming (when controlled by Van's control module)
Problem: Interior lights do not come on at all
Solution: Double check that your EFIS is emitting a pulsed dimming signal compatible with LED lighting. Check the EFIS manual
or contact your EFIS manufacturer directly. Older EFIS's may output a constant voltage that varies in voltage level with the EFIS
dimming level. This constant voltage will never reach ground. The interior lights will only turn on when the control signal goes to
ground.
