T25 Com issue

[cwood2000]

On first flight in RV8 with Advanced 6600 panel, the com worked great for 30 minutes. I was able to transmit and receive with groundcrew just fine. About 30 minutes into the flight, I stopped transmitting voice, reception was excellent. Ground crew could hear me key the mike and the radio screen showed a Tx but no voice. On the ground I checked the intercom and all was good, no problem speaking and hearing. (two lightspeed Zulus) could not voice transmit over the radio from the back seat, same as front. The EFIS showed the COM only putting out .4 amp on TX which should be about 8.0, so it was not getting out. I checked the pre made antenna cable and it appeared good, but I replaced it with another to try, NO-JOY. It is a new RAMI antenna and mounted to unpainted skin on bottom of airframe. Advanced suspects a bad harness and is sending one. Any other help or direction to check out is greatly appreciated, I want to get back in the air quickly, but safely.

 

[Rhino]

Since the key and audio lines travel by separate paths, I can see why Advanced suspects the wiring harness. You can wire in a headset socket on the wiring harness that hangs down behind the panel. This allows you to bypass most of the harness, and any intercom or com panel, and input both keying and audio directly to the radio. Not only does it provide a failsafe for intercom or com panel failure, it also provides a good troubleshooting path for problems like this. It's just a question as to whether or not the builder is willing to go to that effort. I recommend it for new installs. Retrofits can be more difficult, depending on the builder and aircraft involved. If the connectors are accessible, you can jumper audio directly from your headset jack to pin 23 of the T25, just as a test. That bypasses everything except the headsets and jacks/connectors. I assume you've already tried different headsets.

 

[cwood2000]

Since the key and audio lines travel by separate paths, I can see why Advanced suspects the wiring harness. You can wire in a headset socket on the wiring harness that hangs down behind the panel. This allows you to bypass most of the harness, and any intercom or com panel, and input both keying and audio directly to the radio. Not only does it provide a failsafe for intercom or com panel failure, it also provides a good troubleshooting path for problems like this. It's just a question as to whether or not the builder is willing to go to that effort. I recommend it for new installs. Retrofits can be more difficult, depending on the builder and aircraft involved. If the connectors are accessible, you can jumper audio directly from your headset jack to pin 23 of the T25, just as a test. That bypasses everything except the headsets and jacks/connectors. I assume you've already tried different headsets.

Thanks Rhino, I have tried different headsets, and I'll try your suggestions.

Thanks Again!

 

[cwood2000]

The harness was fine, replacing the transceiver solved the problem, I'd sure like to get an autopsy report on the one going back.

 

[terjamgro]

i have a similar problem; SV-COM-T25. sn;01367. conversion harness; sn;061062.
when flying, i can can send and receive but i cannot hear myself in headset. can hear myself ok on ground.
also, much static from tower beyond 5nm. can hear other aircraft fine. this may be an antenna issue, not sure. some help please? thanks
aircraft; super petrel. 2014.