Radio issues

[r0ckst4r]

Was flying today when the COMs all of a sudden basically lost all volume.   I could transmit fine and people could hear me but I could barely hear anything.   I can still hear low volume staticky transmissions and even inter-cockpit communication was staticky and not clear.   If I had to guess it seems like an amplifier in the radio receiver went bad.   I transmit fine and I still receive but it's barely audible. 

I tried more than one headset.   I tried the right and left seat headset jacks.  I tried messing with the volume and squelch and everything I could think of to no avail.  Anyone have this happen before?  Anything else i can check?  Is this something an A&P can look at or will it need an avionics shop?

[takair]

What equipment do you have, radios, audio panel, intercom?  If you lost intercom too, I would be looking at a common failure like the audio panel racking or common ground point that is often used with audio systems. 

[McMooney]

My personal experience,  had the same or really similar issue, spent a boatload of money replacing my main navigator and other things, but in the end it turned out to be the audio panel.   I pulled it out, cleaned the contacts and reseated it, issue gone.

[r0ckst4r]

2 hours ago, takair said:

What equipment do you have, radios, audio panel, intercom?  If you lost intercom too, I would be looking at a common failure like the audio panel racking or common ground point that is often used with audio systems. 

 

32 minutes ago, McMooney said:

My personal experience,  had the same or really similar issue, spent a boatload of money replacing my main navigator and other things, but in the end it turned out to be the audio panel.   I pulled it out, cleaned the contacts and reseated it, issue gone.

I think you guys are on to something.  I went to the hangar today to do radio checks and everything works 100% now, almost making it worse and harder to pin down now that it is intermittant .  Here are more details.

1995 Mooney M20R Ovation

King KMA-24 Audio panel

NAT AA80 Intervox

Is it straightforward to pull the KMA-24 out to clean contacts?  Do you know where the common grounds for these systems would be?   Are there contacts under the cowl I should be looking at?

[wombat]

You should have had a speaker in the cockpit!

[Vance Harral]

In the roughly 20 years we've owned our airplane, we've had a handful of audio issues.

Every single one of them turned out to be a loose ground somewhere.  Loose audio grounds interfere with the audio performance itself.  Loose grounds elsewhere in the system create electrical noise, which can translate to noisy audio.

In as-purchased condition, a number of the ground connections for various electrical components in our airplane were made for convenience rather than robust design.  Several were made via nearby screws that just happened to fasten into metal components.  Over time, I've managed to re-wire most of those to the ground terminal block near the circuit breakers that is really supposed to be used for this, and it makes it much easier to check for bad grounds.  But there are still several different locations where "things" are wired to ground.  Nowadays, when we get electrical noise, the first thing I do is sigh.  Then I take an ibuprofen.  Then I lie down under the instrument panel and start tracing and wiggling all the grounds, one by one.  Suggest you start there.  It's tedious, but straightforward, and free.

[GMBrown]

Just in case chasing the grounds doesn't help, I had a similar experience with my Garmin 530.  Just as I approached the airport I couldn't communicate with the tower.  I could hear them, but they couldn't hear me. It happened on a couple longer flights. It turns out that the 530 was over heating.  A dedicated air hose to the back of the 530 had fallen away from the radio.  I hooked it back up and that solved the problem.

[1980Mooney]

4 hours ago, r0ckst4r said:

 

I think you guys are on to something.  I went to the hangar today to do radio checks and everything works 100% now, almost making it worse and harder to pin down now that it is intermittant .  Here are more details.

1995 Mooney M20R Ovation

King KMA-24 Audio panel

NAT AA80 Intervox

Is it straightforward to pull the KMA-24 out to clean contacts?  Do you know where the common grounds for these systems would be?   Are there contacts under the cowl I should be looking at?

You didn't mention if you tried your other radio when you lost volume.  You mentioned changing headphones and jacks.  If the problem was exactly the same with both radios I would also suspect the audio panel.

You just need an 3/32 allen wrench. 

https://www.csobeech.com/files/KMA-24Install.pdf

 

[takair]

5 hours ago, r0ckst4r said:

 

I think you guys are on to something.  I went to the hangar today to do radio checks and everything works 100% now, almost making it worse and harder to pin down now that it is intermittant .  Here are more details.

1995 Mooney M20R Ovation

King KMA-24 Audio panel

NAT AA80 Intervox

Is it straightforward to pull the KMA-24 out to clean contacts?  Do you know where the common grounds for these systems would be?   Are there contacts under the cowl I should be looking at?

Since you have an old federated system….individual intercom….and the intercom also failed….I would lean toward the ground…..  The downside is that this is likely at the back of the radio rack and hard to access.  You might start t shooting by having one person with headset on and another “jiggling” things under the panel.  These can be frustratingly difficult.  In some cases I’ve re-wired to ease the pain.

[N201MKTurbo]

I was ferrying a plane recently that did that. It was wired for stereo and the plug was one click out.

[Pinecone]

If you need a replacement, I have a KMA-24, 28 volt that came out of my 252.  Make you a special deal.