GMA 240 audio troubleshooting

[powercat]

Hello I am having issues with a GMA 240 audio panel. It’s connected to a single GNS 430, single set of phones and mic jack per the installation manual (no brained) However as soon as it turns on, it goes through its self check (all lights go on and settle at the selected output) but the sound is heavily diminished. With the audio panel off, the GNS 430 radio sounds good and loud with full range of volume control. With the panel on, the sound is barely audiable. It feels as if the amplification through the panel has failed. Any suggestions and ideas? Any shop can maybe bench test it to see if the GMA itself is bad or not? I don’t want to send it to Garmin for a flat $600 fee. Thanks

[BobTurner]

It does sound like you are correct. Double check that the setup is correct (selected com1 or whatever the 430 is wired to, volume turned up, check the squelch if it’s manual (I forget). Look at the pins, make sure nothing is shorting the output pins you would use for other headsets). Question: if it’s just one radio and one headset, why do you even need an audio panel?

[powercat]

Thank you. Yes I triple checked the wiring and everything else. I just didn’t connect a copilot side yet and will eventually get a second nav/com, hence the audio panel. I wonder what my repair options are besides Garmin and a trash can

[Longez]

Is this a new installation of a used audio panel of unknown condition, or was it previously working in your plane?

Is the intercom function working well (when speaking into the pilot headset) with you being able to adjust the intercom volume and squelch knobs? The intercom volume and squelch has little to do with the COM1/COM2 audio, but would be an indication of the overall condition of the audio panel.

If you adjust the COM1 radio volume all the way up (at the radio), do you still not hear the radio loud enough?

Has someone adjusted the MASQ (Master Avionics Squelch) Mute LVL? I have never seen this, but perhaps it has been raised so high that it is preventing the radio audio from being heard. As explained in the install manual, you can temporarily disable this squelch as a test by grounding pin 16 on connector 2401.

I would try connecting the single radio to the COM2 connections (move 4 wires) to see if it works well when selected as COM2.



Steve

[powercat]

Hi Steve, yes this is indeed a new installation of a used panel in the plane. Of course having tried with the volume of COM 1 all the way up makes no difference to the output volume of the audio panel. COM 1 (GNS 430) volume otherwise works without issue when the audio panel is off. Trying to route through COM 2 is a good idea. I tried playing with the MASQ pot in every position without avail.

[BobTurner]

Is this the intercom with the internal fuse? I forget the model number, one of the early Garmin intercoms used an internal fuse to protect the electronics against an accidental short at the output, and there were a number of fuse failures until Garmin okayed using a higher current fuse. Wouldn’t hurt to open it up, and see if you can see an internal fuse, and use an ohmmeter to see if it’s blown.

[Longez]

Originally Posted by BobTurner

Is this the intercom with the internal fuse? I forget the model number, one of the early Garmin intercoms used an internal fuse to protect the electronics against an accidental short at the output, and there were a number of fuse failures until Garmin okayed using a higher current fuse. Wouldn’t hurt to open it up, and see if you can see an internal fuse, and use an ohmmeter to see if it’s blown.

Good idea, but there is no reason to check the internal fuse if the lights flash at power-on and the intercom works normally.

The internal fuse is connected directly to incoming aircraft power from connector 2402, pins 8,9, so there would be no signs of life when the power switch is used if this fuse were blown.

Steve

[PaulYardy]

I'd borrow or steal a second compatible intercom and slide it in. If things remain the same it's your wiring.

[Kbean]

Does anyone have a pic of what the internal fuse on a GMA 240 looks like?
My audio panel has gone dark. Opened it up and there is small square
with number 560 on top. The 560 is hard to read because it looks like it got hot.
My avionics shop is hesitant to look at it and wants to send it to Garmin.
There goes 800$ ?
Thanks for any advice.
Kevin

[Longez]

Originally Posted by Kbean

Does anyone have a pic of what the internal fuse on a GMA 240 looks like?
My audio panel has gone dark. Opened it up and there is small square
with number 560 on top. The 560 is hard to read because it looks like it got hot.
My avionics shop is hesitant to look at it and wants to send it to Garmin.
There goes 800$ ?
Thanks for any advice.
Kevin

Kevin,

No, your arrow is not pointing to the fuse. See green area below.

It looks good in this picture, but you can confirm by verifying that it has power on both sides with your voltmeter when aircraft power is applied to the unit.



In very old units this was a 1A fuse. In everything produced for many years, this was changed to a 4A fuse, and to my knowledge, none have ever blown. The 1A was also quite hard to blow.

Steve