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Jim Heekin
Joined: 03 Mar 2017
Posts: 2
Location: Orlando, FL
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 Posted: Mon Mar 06, 2017 11:18 am Post subject: Troubleshooting Assistance Radio |
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Folks,
I would really appreciate some advice — I've been wandering in the wilderness for a couple of days now.
Original condition of the radio stack: KMA-24 audio panel, two KX-155s (comm 1 and 2), NAT AA80-001 intercom, Narco 150 transponder and TCI digitizer.
The mission was to replace the Narco 150 with an NGT-9000 for compliance with the ADS-B mandate. Because of the NGT’s enhanced display, I positioned it at the top of the radio stack just below the KMA-24 audio panel. The two KX-155s were moved down a notch to a position just below the NGT.
In the process I took the “opportunity” to remove a significant amount of “orphan” wire that remained after previous avionics upgrades, both behind the panel and in the floor.
The good news — the NGT checks out and works as advertised. The more challenging news — I've lost the ability to transmit voice modulation from the KX-155s.
The intercom functions properly from all four positions in the aircraft using various headsets. The radios transmit when the buttons on the yokes are pushed. The intercom indicates transmission (light shows green) and a signal is getting out (I can key the airport’s weather advisory report with four clicks). But, no voice transmission results when the transmit button is keyed and there is no sidetone in the headsets.
The standby mic wired into the intercom system for emergency power outage does not seem to function for voice transmission either.
Initially, I thought I may have disturbed the connections between the intercom and the audio panel in the process of removing and lowering the KX-155s. I removed both the audio panel and the intercom and put a tracer on the logical wires (radio mic hi, radio keyline and radio audio hi in the intercom harness). All indicated continuity from the intercom harness into the audio panel connector.
I would greatly appreciate any suggestions on next steps that I might check or try. I can post the pin configurations for each appliance if that would be helpful to the analysis.
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stein(at)steinair.com
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| Posted: Mon Mar 06, 2017 11:52 am Post subject: Troubleshooting Assistance Radio |
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If the TX lights come on the KX's and your intercom is working great between headsets just sitting there, it almost has to be the Mic Audio Hi wires for the KX's (either between the radios and the KMA or between the KMA and the NAT). I'd look between the NAT and the KMA first...
Cheers,
Stein
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