Omega232Devils

Omega232Devils

Well Known Member
Greetings RVr's!
I hope I am not opening a can of worms here, but hoping someone can point me in the right direction before I loose myself in a web of wires.

My setup: GMA340: Comm 1: Garmin 430 / Comm 2: Garmin SL40

When I purchased my plane three months ago, the passenger PTT did not work and I can't verify it ever did. The ICS works fine. Initially I thought the problem was the switch itself, so I replaced it. This didn't fix the problem. When the passenger PTT is pushed there is no indication on either Comm1 or 2 that I am transmitting. I just wanted to see if there were any guru's out there that had the 'quick fix' before I start chasing wires.

I am learning my comm suite, but am far from an expert so please don't assume any idea is beneath me.

Fire away!

Dan
 
When you push the PTT check for continuity to ground. The audio panel is looking for a low, so if you're not getting a ground when you key this could be your problem.
 
The PTT wires go to the audio panel. The audio panel then drives the appropriate radio. There are several wiring choices that the builder / installer gets to choose during the install process.

a) both pilot and passenger PTT's activate the same radio

b) pilot's PTT activates one of the radios and passenger activates a different radio

One way to verify how your installation is wired is to use the sample wiring diagram in the Garmin install documentation and ohm out each of the device tray pin contacts to see how the plane is wired. At this point, you can also verify that the PTT switch is making contact with the proper pin in the audio panel tray.
 
check basics

Dan,
The pax stick is normally constructed to be removable. Therefore there are normally connectors on the PTT wires at the base of the stick. It is possible that the stick was reinstalled and the wires not connected, or that somehow the wires became disconnected during flight, don't ask me how I know,:rolleyes:
 
Thanks for the replies

I appreciate the help guys.

Trevor,
PM sent. Can you expand on this?

Noelf,
Good point and I was hoping I wasn't opening a can of worms by asking 'How is my plane wired?" haha. My understanding and from what I have read on the GMA-340 is that it can separate the communications the way you described. i.e. with a push of a button, both pilot and copilot can talk on radio selected, or pushing the 'comm1/2' button separates the pilot and copilot microphones allowing them to work separate radios individually. I would hope my plane is wired this way and not direct to comm1/2 for pilot and comm2 only for passenger. (side note: there is no 'TX' on either radio when keyed from passenger side)

Bob,
Thanks for the reply and I am hoping it is 'basic' goof up that I am missing! Unfortunately, my passenger PTT is mounted on the bulkhead!


Update: The one thing that is confusing me is the microphone works just fine in the ICS. I can adjust the VOX setting with the 340 as advertised. So there is some connection or interruption in that flow that should allow the microphone output to the radio vice ICS. This is sticking in my mind as the point of issue.

Thanks again guys. I look forward to hearing more thoughts!

Dan
 
As you have mentioned, this is not a passenger microphone issue. You need to look at the passenger PTT switch and the connections to the audio panel.

When the passenger PTT is depressed, the signal should go to the audio panel. The audio panel then sends a signal to the associated radio (selected by the pilot as com 1, com2) transmit key signal input. If the split tx function has not been connected, then there is only one signal path from the audio panel to the selected radio.

I suspect that the passenger PTT function is not wired correctly between the PTT switch (which may also have been wired into the passenger mic phone jack) and the audio panel.
 
Problem solved!

Thanks RVrs!
Thanks for the help! I checked the switch and didn't have any power running to it, open or closed. So I pulled the panel beneath the passenger seat and traced the wires. The ground wire looked good. I traced the hot wire and it also looked good, but was joined in two places with connectors heading to the 340. I found a loose connector and was able to do a quick repair. Quick radio check and problem solved. Took longer to pull and replace the panel than the repair! Thanks again for the help.

Dan
 
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