GMA 345 no radio transmit

Bought from spruce, had them make a harness, wired to brand new GTR 225, I hear myself, Radio indicates coming in but nothing comes through GMA 345. Bluetooth works, mics work, mic key works. No indications when diagnostics are run. Thanks for help in advance.

Clparker23 said:

Bought from spruce, had them make a harness, wired to brand new GTR 225, I hear myself, Radio indicates coming in but nothing comes through GMA 345. Bluetooth works, mics work, mic key works. No indications when diagnostics are run. Thanks for help in advance.

Click to expand...

Hello CLparker23,

Welcome to VAF!

It would probably be best to contact Aircraft Spruce or Garmin directly, but we are happy to try to help.

As you are probably aware, there are 4 dedicated knobs on the GMA 345 that control music and intercom volume for the pilot/copilot. These have no effect on the volume of the COM1 or COM2 radio.



The radio volume is controlled at each radio.

• Does increasing the volume on the GTR 225 allow you to hear the radio?
• If you break squelch on the GTR 225, you should be able to hear yourself adjusting the radio volume even when not receiving a transmission.
• Have you tried enabling both COM1 audio and COM2 audio in case the radio is connected to the other position?
• Have you made sure that the GTR 225 internal intercom is disabled?

If you have already considered and tried the above steps, then there is probably a wiring problem in your harness that is not allowing the COM audio signal to reach the audio panel.

Thanks,
Steve

Thanks Steve,
I have tried both comm 1 (GTR 225) and comm 2 (kx170). Neither coming through.

I read about disabling internal intercom on GTR 225 last night. I?m headed that way to try that.

I have reached out to spruce and Garmin and waiting for a reply. But just got to the point to reach out to the entire community.

The kx170 is wired with a speaker load. However the ?lo? wires from the GMA 345 to the kx170 are folded over and ?not? connected at all...should they be grounded to the kx170 chassis?

Thanks again!

Clparker23 said:

Thanks Steve,
I have tried both comm 1 (GTR 225) and comm 2 (kx170). Neither coming through.

I read about disabling internal intercom on GTR 225 last night. I?m headed that way to try that.

I have reached out to spruce and Garmin and waiting for a reply. But just got to the point to reach out to the entire community.

The kx170 is wired with a speaker load. However the ?lo? wires from the GMA 345 to the kx170 are folded over and ?not? connected at all...should they be grounded to the kx170 chassis?

Thanks again!

Click to expand...

Hello Clparker23,

Not sure what a KX 170 is, but we found a 1976 installation manual for a KX 170A/B.

We see what you mean about the KX 170A/B only having a COM Audio Hi output, and no COM Audio Lo output.

We recommend using the same shielded pair audio wiring shown in the GMA 345 installation manual, with the shield braid terminated only at the GMA backshell. Since the KX doesn't have a dedicated COM Audio Lo pin, you can connect that wire (coming out of the shielded pair) to the KX chassis.

The KX 170A/B has a dedicated 500 ohm COM Audio Hi, so the COM audio should not be provided via a "speaker load".

If you want to email (see below) us the wiring diagrams for your harness, we can provide further review.

Thanks,
Steve

Steve,
I pulled everything out and looked it over, I removed the kx170 from the audio panel to focus on 1 radio. I have the GMA 345 and GTR 225 only hooked up. I can only hear an extremely faint RX when the GMA is not turned on. When it?s turned on, absolutely nothing.
Thanks,
Clayton

Clparker23 said:

Steve,
I pulled everything out and looked it over, I removed the kx170 from the audio panel to focus on 1 radio. I have the GMA 345 and GTR 225 only hooked up. I can only hear an extremely faint RX when the GMA is not turned on. When it?s turned on, absolutely nothing.
Thanks,
Clayton

Click to expand...

Hello Clayton,

There are only 2 wires that bring COM audio from the GTR 225 to the GMA 345 COM1 audio input.

I would start by confirming good connections between those two sets of pins and making sure neither wire is shorted to ground.

Please email us at [email protected] if you need our assistance in confirming the correct pins on each unit.

Thanks,
Steve