What's new
Van's Air Force

Don't miss anything! Register now for full access to the definitive RV support community.

Mic/Intercom Issue

Craw

Craw

Active Member
Hello,
I have a GMA245 intercom with a GNC650Xi for COM 1 and GNC255A for COM 2. I have wired both GA style headset Jacks and 6 pin LEMO Jacks. I have no issues with audio IN on either COM or the GMA.

However I can't hear myself in the intercom unless I press the PTT button and even though the radio indicates its transmitting (blinking GMA & COM and TX annunciation on associated COM) but no audio is transmitted? I have held the Play button down to check the GMA245 annunciators and they all remain off.

I have attached my interconnect diagram below, any help or suggestions are welcome.

Cheers
 

Attachments

  • GMA Wiring.pdf
    245.2 KB · Views: 100
I have no idea if this is causing the issue, but the dotted lines on the top of page one of your diagram aren't correct.

The "tip" is the tip of the plug, and it would be the bottom contact in the picture, not the top. Top is "ring."

The other pictures further down show tip wired for mic hi, and I believe that that should be ring.
 
Good observation I had questioned it myself, however, the diagram does point to the correct tab that stick outs to solder on to. It is a little confusing until you get a jack and set it in the same angle as the diagram it will then make sense.
 
Craw said:
Hello,
I have a GMA245 intercom with a GNC650Xi for COM 1 and GNC255A for COM 2. I have wired both GA style headset Jacks and 6 pin LEMO Jacks. I have no issues with audio IN on either COM or the GMA.

However I can't hear myself in the intercom unless I press the PTT button and even though the radio indicates its transmitting (blinking GMA & COM and TX annunciation on associated COM) but no audio is transmitted? I have held the Play button down to check the GMA245 annunciators and they all remain off.

I have attached my interconnect diagram below, any help or suggestions are welcome.

Cheers
Click to expand...

Could you also share how you have the GMA 245 DIP switches set?

For example, we would want to make sure that keyed ICS (dip switch 1) is disabled.

It would also be good to make sure that your intercom volume is turned up.

Steve
 
Just fixed a install for a friend, he got confused as to which solder ring was connected to which plug contact. Easy to confuse
 
Dip switches 1(dip switch function ON) & 3 (COM mute TX) are active. Intercom volume is fine as I can hear myself loud and clear in the headset when I push the PTT button but it wont transmit my voice. Otherwise I can't hear myself on the intercom. I turned off the dip switches and now I hear myself in the intercom loud and clear! however transmit signal still comes out blank? It does indicate its transmitting on the GMA and the GTN but its blank?
 
Last edited:
Craw said:
Dip switches 1(dip switch function ON) & 3 (COM mute TX) are active. Intercom volume is fine as I can hear myself loud and clear in the headset when I push the PTT button but it wont transmit my voice. Otherwise I can't hear myself on the intercom. I will try with the dip switches turned off however and see if it changes anything.
Click to expand...

That would be very bad to have DIP switch 1 in the down (ON) position since you are not using keyed ICS.

Make sure that all DIP switched are in the up (OFF) position except DIP switch 3.

GMA245 DIP Switch.png

Steve
 
Craw said:
Intercom volume is fine as I can hear myself loud and clear in the headset when I push the PTT button
Click to expand...

When you push the PTT button, the audio you hear is not the intercom but rather the sidetone from the radio. So I would second Steve's suggestion to look at intercom volume and whether keyed-ICS is enabled.
 
Hey all,
So yes the intercom now works with the only the #3 dip switch activated, however I still cannot hear my radio call on a separate handheld radio even though the audio panel and radio indicate their transmitting. Any ideas?

Note that I can hear myself on the intercom now and all other audio functions appear to work. Just seems like its transmitting a blank signal?
 
I did not swap pins 33 & 34, actually I only have pin 34 connected at the moment as I haven't run the wire for pin 33 to the passenger stick grip yet.
 
Hey guys
There are two different jacks both with pins 33 and 34. I suspect one of you is looking at the top connector, the other at the bottom one.
 
Craw said:
Hey all,
So yes the intercom now works with the only the #3 dip switch activated, however I still cannot hear my radio call on a separate handheld radio even though the audio panel and radio indicate their transmitting. Any ideas?
Click to expand...

It looks like you might not be flying yet. How are you powering the avionics?

The GTN will not enable the transmitter if the input voltage is too low.

Steve
 
Correct I am bench testing the avionics and I have deep cycle battery powering the rig. It will hold 12.3 v at 7amps when transmitting. I am only powering the VP-X with the PFD, GMA245 and GTN breakers on.

Note that I do have the antenna connected to RG400 with a length of ~10ftand grounded back to the sub panel.
 
Last edited:
Craw said:
Note that I do have the antenna connected to RG400 with a length of ~10ftand grounded back to the sub panel.
Click to expand...

The antenna should be mounted on a ‘ground plane’, e.g., fairly large piece of metal like the fuselage, and the coax braid attached to the ground plane close to the antenna. There is no need for an additional wire back to the sub panel.
 
Thanks Bob & all, sounds like I got ahead myself with the initial systems configuration. I will try again once I have everything in the aircraft.

Cheers
 
You must log in or register to reply here.
Back
Top