Problems with PMA-8000

[Mark Russell]

Hi guys. I have an audio problem and can't figure it out, so maybe the masses could help?

In an rv-8 I have a PMA-8000. Everything works fine, except the auot-squelch on the intercom does not seem to work. I have tried mic-muffs, etc. to no avail and the ambient noise of the operating engine keeps the mics open all the time. I double checked my wiring and couldn't find the problem, I sent the unit back to stark and they bench tested the unit and could not find an issue. As of now, I have to turn the intercom volume down nearly all the way, especially if I want to be heard well while transmitting over the radios.

Anyone else have a similar problem with the inteli-vox on the ps engineering units? I suspect a wiring problem on my end, but have not been able to find it.

In short the mics are always open.

-frustrated in California (besides higher taxes)

-mark russell

[mscheuer]

Hi Mark:

I think you and I talked last week.

I suggested that you take a look at a particular pin of one of the rear connectors. If that pin is grounded, it forces all microphones to go hot, we use this function for test purposes during our manufacturing process.

Have you had a chance to pull the PMA8000 (I believe this is not the "B" version) and made sure this isn't the problem?

I doubt it's the IntelliVox. It is statistically impossible to have all 6 individual VOX circuits to fail simultaneously. In fact, I don't recall the last time we did have an IntelliVox failure. And there are more than 66,000 out in the field as we speak!

I look forward to getting this problem resolved, and it will be figured out, I promise.

Sincerely,

Mark Scheuer
PS Engineering, Inc.

Originally Posted by Mark Russell

Hi guys. I have an audio problem and can't figure it out, so maybe the masses could help?

In an rv-8 I have a PMA-8000. Everything works fine, except the auot-squelch on the intercom does not seem to work. I have tried mic-muffs, etc. to no avail and the ambient noise of the operating engine keeps the mics open all the time. I double checked my wiring and couldn't find the problem, I sent the unit back to stark and they bench tested the unit and could not find an issue. As of now, I have to turn the intercom volume down nearly all the way, especially if I want to be heard well while transmitting over the radios.

Anyone else have a similar problem with the inteli-vox on the ps engineering units? I suspect a wiring problem on my end, but have not been able to find it.

In short the mics are always open.

-frustrated in California (besides higher taxes)

-mark russell

[Mark Russell]

Hi Mark,

Yes, you and I spoke. I did check to make sure that pin 16 was not grounded and sent the unit to stark where they bench tested it and could not find any problem.

I suspect it is some sort of a wiring mistake on my part and am building a new tray with just power and headsets to confirm.

But.... if you can think of anything else, I'm all ears (literaly).

kind regards,

mark

[mscheuer]

Thanks Mark for getting back to me.

Was there a pin installed at that location? I'll be the first to admit it can be confusing when looking at the drawing in the installation manual. It is a rear view, so you have to think backwards when you look at the connectors from the front. If you look at Appendix B in the PMA8000 manual, you will see the drawing that I'm referring too.

Except for that pin, I can't think of how our panel could be wired in order to make all mics hot.

Get the serial number to me and I'll get you an RMA. I know it's out of warranty (more than 3 years old) but if you send it back I'll tell the techs to put it through its paces without any charge. If there is something that has failed, we'll figure it out then charge you the flat repair fee of $179.

If I understand the problem correctly, all of the mics are always on, that sure sounds to me that pin is shorted to ground.

Mark

Originally Posted by Mark Russell

Hi Mark,

Yes, you and I spoke. I did check to make sure that pin 16 was not grounded and sent the unit to stark where they bench tested it and could not find any problem.

I suspect it is some sort of a wiring mistake on my part and am building a new tray with just power and headsets to confirm.

But.... if you can think of anything else, I'm all ears (literaly).

kind regards,

mark

[noelf]

...that the mic's were always "hot". Is this true without the engine running, or other loud ambient noise conditions.

A possibility is that the headset mic is twisted around and "pointed" towards the front of the a/c, and not at your lips.

[Rick S.]

I had/have a similar issue but I'm sure your mics are not always hot but it seems that way, trust me I know what you are talking about.

I have put the mic muffs on everything, helped a bunch, lips close to the mic, etc. My mics are not always "hot" it just seems the intellivox system is way too sensative to noise and errant breezes. Adjusting airflow in the cabin helped more than anything but I found my mic activating when I would breath from my nose and the air would hit the mic, with O2 running it would pick up the little "psst" from the Mt. High system. It seems that a nice thing to be able to do would be dial down the system sensativity a bit...It may like noisy cockpits but it doesn't like any breezes blowing around the mics.

Before the mic muffs the system was almost unuseable to to the mics constantly activating and deactivating.

[Mark Russell]

Hi Mark, I'll double check on the pin location again, but yes, there was a pin at the spot that I checked. When I'm down at the hangar again this weekend i'll double check again. Also, i'm rigging up a couple new J1 and J2 connectors to test on the bench and see if there is an issue. (trying to isolate any wiring issues).

thanks all for suggestions,

Kind regards,

Mark Russell

Originally Posted by mscheuer

Thanks Mark for getting back to me.

Was there a pin installed at that location? I'll be the first to admit it can be confusing when looking at the drawing in the installation manual. It is a rear view, so you have to think backwards when you look at the connectors from the front. If you look at Appendix B in the PMA8000 manual, you will see the drawing that I'm referring too.

Except for that pin, I can't think of how our panel could be wired in order to make all mics hot.

Get the serial number to me and I'll get you an RMA. I know it's out of warranty (more than 3 years old) but if you send it back I'll tell the techs to put it through its paces without any charge. If there is something that has failed, we'll figure it out then charge you the flat repair fee of $179.

If I understand the problem correctly, all of the mics are always on, that sure sounds to me that pin is shorted to ground.

Mark

[mscheuer]

Hi Mark:

Interesting! And good news. There should NOT be a pin at that location.

Please remove.

Mark

Originally Posted by Mark Russell

Hi Mark, I'll double check on the pin location again, but yes, there was a pin at the spot that I checked. When I'm down at the hangar again this weekend i'll double check again. Also, i'm rigging up a couple new J1 and J2 connectors to test on the bench and see if there is an issue. (trying to isolate any wiring issues).

thanks all for suggestions,

Kind regards,

Mark Russell

[mscheuer]

Dear Rick:

Sorry that our IntelliVox isn't working as well as we both would like it too. If your panel is less than 2 years, there is actually a High-Noise configuration that be selected by moving a couple of dip switches located inside the panel.

Let me know what serial number you have and I will confirm yours has this capability, and I will send instructions how to do it (pretty easy).

It is very rare that I give this information out. Preferably, the Oregon Aero Mic Muffs is the best route, but if there is just that much back ground noise, this option might be worth trying.

About direct wind noise.....All VOX circuits, analog or digital, use some means to determine if a particular level (voice) becomes higher than a preset level (Squelch). When wind noise hits a microphone, the wind buffets the face, the mic itself, and even whiskers if you've got a beard which creates audio frequencies that are in the same exact "band" as our voice. Thus opening up the mic.

With analog control, you can tighten the squelch, but this will lead to either clipping or readjustments. Not the end of the world, but it something that must be addressed.

Ideally, if you move the vent ever so slightly so it is hitting your face and not the microphone, you can eliminate this tripping. The Oregon Aero Mic is a great tool to reduce the amount of noise the microphone places into the intercom.

You might also look at the microphone you are using, does it have a gain control? Almost all of the newer Lightspeed headsets do, and that is great. Turn the gain all the way down.

If you are using a Bose headset, please carefully remove the wind sock on the mic and look at the serial number. If it has a -3, give me a call and we can probably help you there too.

While our IntelliVox is not perfect, from what we have been hearing in PIREPS over the last 13 years and with over 66,000 systems out in the field, it's really works exceedingly well.

I hope with a few minor adjustments, you too will feel the same.

Sincerely,
Mark Scheuer
PS Engineering

Originally Posted by Rick S.

I had/have a similar issue but I'm sure your mics are not always hot but it seems that way, trust me I know what you are talking about.

I have put the mic muffs on everything, helped a bunch, lips close to the mic, etc. My mics are not always "hot" it just seems the intellivox system is way too sensative to noise and errant breezes. Adjusting airflow in the cabin helped more than anything but I found my mic activating when I would breath from my nose and the air would hit the mic, with O2 running it would pick up the little "psst" from the Mt. High system. It seems that a nice thing to be able to do would be dial down the system sensativity a bit...It may like noisy cockpits but it doesn't like any breezes blowing around the mics.

Before the mic muffs the system was almost unuseable to to the mics constantly activating and deactivating.

[L.Adamson]

Originally Posted by Rick S.

I had/have a similar issue but I'm sure your mics are not always hot but it seems that way, trust me I know what you are talking about.

I have put the mic muffs on everything, helped a bunch, lips close to the mic, etc. My mics are not always "hot" it just seems the intellivox system is way too sensative to noise and errant breezes. Adjusting airflow in the cabin helped more than anything but I found my mic activating when I would breath from my nose and the air would hit the mic, with O2 running it would pick up the little "psst" from the Mt. High system. It seems that a nice thing to be able to do would be dial down the system sensativity a bit...It may like noisy cockpits but it doesn't like any breezes blowing around the mics.

Before the mic muffs the system was almost unuseable to to the mics constantly activating and deactivating.

We have the 8000B model. Both my wife and I consider it perfection compared to our prior intercom (not PS Engineering). But then I mentioned this a few months ago.. In our case, it's either my wife's headphones laying over the right side GPS (she's not in the plane) and directly into the air vent, or the air vent aimed directly at the mic while she's wearing it. Other than that the mic control is very good, as well as being completely automatic.

I also use the Oregon Aero mic muffs, and the oxygen system has no effect on the mic. Headphones are Telex ANR's. Without ANR's my 6A is very noisy!

L.Adamson --- RV6A