PMA7000B Squelch Issues

[BigTex]

Last week I upgraded my KMA24 to a PMA7000B audio panel and few it for the first time to Kerrville.  Overall, it's really working well but am having an issue with the squelch.  It seems to be cutting in and out every few seconds when I'm at cruise RPM.  I've unplugged everything headset but mine and still hear it.  The only way I've found to not hear it is to switch the audio until to ISO mode.

 

Anyone else experience an issue like this?

[N201MKTurbo]

I would call PS Engineering and ask them. I would suspect a ground loop.

[cbarry]

Try adjusting your headset mic gain (usually a dial on the mic itself) to lower its sensitivity. Of course, there's also a mic gain adjustment on the audio unit as well that may have not been adjusted during the install.

[Mooneymite]

Try adjusting your headset mic gain (usually a dial on the mic itself) to lower its sensitivity. Of course, there's also a mic gain adjustment on the audio unit as well that may have not been adjusted during the install.

I think this is a good place to start. In my limited experience, squelch issues turn out to be headset issues.

[carusoam]

Gary,

Aside from the squelch issue...

How challenging was the install of the PMA?

I'm expecting nearly a slide in, since BK is doing a repackage of the similar device.

Good luck finding the right settings,

-a-

[flyboy0681]

I have found the PMA auto-squelch capabilities to be outstanding. When we were considering the 8000 I was extremely hesitant because it didn't have a manual squelch knob and I was concerned that the unit would constantly cut in and out on its own or wouldn't be sensitive enough when it needed to be. Nothing could have been further from the truth and it's turned out to be quite remarkable. Nothing gets by it - unless the door pops open  

[Jerry 5TJ]

How challenging was the install of the PMA?

I'm expecting nearly a slide in, since BK is doing a repackage of the similar device.

 

I installed a PM8000BT into the "C" last year.   It was not hard in that first I removed ALL of the old avionics wiring and all old avionics and started anew.   The PS Engineering reference design worked fine.    No issues with the auto squelch so far.  Great stereo audio.   

 

As for it being a "slide in" replacement, that's a bit over-stated as the PM7000 and PM8000 series have a second connector in the back for the intercom and aux audio ports.   You can "slide in" a PM7000 into a KMA24 rack and it will do the audio switching but it won't function as an intercom until you wire up the new connector. 

[BigTex]

Gary,

Aside from the squelch issue...

How challenging was the install of the PMA?

I'm expecting nearly a slide in, since BK is doing a repackage of the similar device.

Good luck finding the right settings,

-a-

I went in with the same expectation that it was a "slide-in" replacement for the KMA24. To some extent it is assuming you don't want to take advantage of any of the additional features like stereo, etc.

There are two connector blocks on the back of the PMA. You can replace the KMA connector with the PMA bottom connector and it should work... In theory. But since my plane was wired for mono, I had to completely rewrite all four mic and headset jacks and pull out my old Intercom system.

Overall I'm really happy with the unit. I plug in a HTC Bluetooth adapter into my Aux input and play music from my iPad. The mute when ATC talks is really nice.

[donkaye]

Last week I upgraded my KMA24 to a PMA7000B audio panel and few it for the first time to Kerrville.  Overall, it's really working well but am having an issue with the squelch.  It seems to be cutting in and out every few seconds when I'm at cruise RPM.  I've unplugged everything headset but mine and still hear it.  The only way I've found to not hear it is to switch the audio until to ISO mode.

 

Anyone else experience an issue like this?

 

PS Engineering recommends using Oregon Aero Mic Muffs on the PMA7000B.  They are inexpensive.  That will most likely solve your problem.  It did for me.

[BigTex]

Thanks Don. I'm using a Halo headset and was wondering if it might be that. I was going to try another headset to see if it stops. I'll order the MicMuff for my headsets to see if that fixes the issue.

[N201MKTurbo]

Did you unplug your mic to see if it went away?

[BigTex]

Actually no... But that's a good idea. I'll give that a try.

[donkaye]

Did you unplug your mic to see if it went away?

 

I can almost guarantee that it will go away by doing that.

[N201MKTurbo]

Well probably, but it will prove that it is an audible noise issue and not an electrical noise issue caused by an installation problem.

[BigTex]

Reporting back... 

 

Purchased the mic muffs and now I'm getting a clicking sound that gets worse as the RPM's increase. The clicking stops when the mic's are unplugged.  My avionics guy initially thought it might be a wiring issue until he hear it first hand.  He's not thinking that the sound levels are too high and is causing the squelch issue.  He's contacting PS Engineering to see if there's any adjustments that can be made to the unit.  Any additional thoughts, please send them my way.

[donkaye]

Reporting back... 

 

Purchased the mic muffs and now I'm getting a clicking sound that gets worse as the RPM's increase. The clicking stops when the mic's are unplugged.  My avionics guy initially thought it might be a wiring issue until he hear it first hand.  He's not thinking that the sound levels are too high and is causing the squelch issue.  He's contacting PS Engineering to see if there's any adjustments that can be made to the unit.  Any additional thoughts, please send them my way.

 

Gary,

 

I'm sorry to hear that.  I never had any problem with the unit.  Before the muffs, there was sometimes a squelch break.  After the muffs, never a problem.

[N201MKTurbo]

Clean your headset plugs with scotch brite or very fine sandpaper. Make sure the panel nuts on your jacks are tight.

Try your head set in the co-pilot jacks and see if it is different.

When it is clicking try fiddling with the mic and headset plugs to see if you can get it to change its behavior.

[BigTex]

All jacks are new and the clicking is coming from either the pilot to copilot jack depending on which mic is plugged in. We used multiple headset combinations from Light Speed to Halo and all are doing it. My avionics guy is talking to PS Engineering. Hopefully they can figure it out.

[N201MKTurbo]

Just a shot in the dark...

 

Have you tried turning off the transponder and DME?

[BigTex]

not yet... After my avionics guy talks with PS Engineering today, I'm sure they'll have a laundry list of things to try.  We'll add those to the list. 

 

I have a separate alternator switch, I might flip that off to see if that makes a difference.

[BigTex]

Well, we were able to identify the source of my static (sounds like frying bacon) when not in ISO mode. It can be traced back to the charging system. Turning off the alternator and all the static is gone. I'll update the post as soon as the root cause if found...

[FoxMike]

I have a PS 7000 and often have a problem with squelch.  I find it is caused by the overhead vents blowing air across the mic.  Muffs help but repositioning the vent slightly solves the problem.  Open doors while taxiing is almost guaranteed to set the problem off.  The best fix would be install an air conditioning system and/or pressurize the airframe.

[BigTex]

I have a PS 7000 and often have a problem with squelch. I find it is caused by the overhead vents blowing air across the mic. Muffs help but repositioning the vent slightly solves the problem. Open doors while taxiing is almost guaranteed to set the problem off. The best fix would be install an air conditioning system and/or pressurize the airframe.

I only wish I get that kind of flow though my overhead vents! Talking to PS Engineering, they seem to think it's a grounding issue. Tomorrow well to some tests to make sure that the jacks are not grounded to the airframe.

[Piloto]

Check if one of the passengers headset is plugged in. If they are of the ANR type they may susceptible to alternator ripple. Unplug all passenger headsets and any music source to see if the problem goes away.

 

José