Audio Help Needed - Page 3

Mich48041 · #21 08-27-2016, 03:37 PM

Dan,
Have you checked the stall warn vane switch? What happens when you lift the vane, any change?
Do you still have two audio problems, loud squeal and faint voice audio?
Have you tried pulling the 3 amp Audio fuse to see what affect that has?

Mich48041 · #22 08-27-2016, 05:54 PM

Dan, if you still have not found the problem, try this:
Disconnect the intercom D-Sub connector from the AV-50000A. Take the back shell off from that D-Sub and remove the wires from positions 24 and 25 using the red/white tool. Jumper those two wires together. Do not put the two wires back into the D-Sub connector. Plug the D-Sub connector back into the AV-50000A. Now try the radio to see if you can hear it OK. Jumpering those two wires together sends the SL40 audio output directly to the intercom, bypassing the audio portion of the AV-50000A. If you can now hear the radio OK, then that means that the problem is either inside of the AV-50000A or else one of the audio inputs to the AV-50000A.

MMiller · #23 08-27-2016, 07:51 PM

Dan,

Are you sure it's a side tone (mic feedback into the head phone) or is it just a loud tone? Any chance you have a grounded wire on the stall input and you are hearing the stall warning? Vans did not provide internals for modules in the control box, but on the D180 version, the audio mixer is wired to the avionics fuse before the avionics switch, so the mixer can't be turned off. With the avionics switch off the tone can't be coming from any of you avionics devices.

Here is an easy test for you...pull the stall fuse and see if the tone stops.

Mich48041 · #24 08-28-2016, 06:18 AM

Mike, we are thinking alike. I had questioned the stall warning in posts 12 and 22. In the SkyView equipped RV-12, the fuse is labeled "Audio" instead of "Stall Warn", and it most likely powers the audio mixer too.

Handclutch · #25 08-28-2016, 06:33 AM

I agree that it's worth checking that you aren't hearing the stall warning. Earlier this year I installed a Garmin 420 (430 without VOR/LOC/GS receiver) replacing an Icom A210. I got a radio guy to do the wiring changes. Fired up the 420, got the audio but also a continuous tone. Naturally figured it had to result from work just done. Spent 3 hours chasing the problem only to eventually find that the stall warning switch had failed and was emitting a continous tone. Disconnected switch and all was good. The radio guy had his gear laid out on the wing and had bumped the switch, breaking it.

I've also been around the mulberry bush on isolating the jacks, but first a caveat - the guy who built my plane did his own thing and ran nearly all the wiring through a large junction box (LOTS of soldering). It will be wired differently from most, if not all other, RV12s. I was never happy with the intercom (Flightcom). Not good sound and lot of hash during first seconds of transmission, especially with passenger headset in use.

Back in June I was heading off on long trip with my son. I'd noticed the revised plans from Vans calling for isolation of both jacks - my mic jacks were isolated but not the phones - so decided to isolate phones in hope of improving audio. Disaster. No audio at all and we were leaving next morning. Quickly regrounded phones and back in business.

Next step was to instal a PS Engineering intercom. I had used them in previous aircraft and found them to be great. Installation instructions explicitly said both jacks MUST be isolated. Radio guy felt that if we wired PS Eng unit in same way as Flightcom and altered nothing else, everything should work. He was half right. Audio came up strong with phones grounded but no transmit. Contrary to instructions we removed isolating washers from mic jacks and everything is now working perfectly - best intercom/radio function I've had since buying the plane, assisted no doubt by acquisition of new David Clark One X which is a generation ahead of my old David Clark ANR.

Jack

D&M Dan · #26 08-28-2016, 06:39 AM

The tone could be the stall warner tone, as I'm not sure what that would sound like. But I do not have the wings on the airplane so it would not be an issue with the switch itself.
Just wondering if it is possible to run a dedicated ground from the headphone jacks to an audio ground, this way bypassing the chassis ground. Where would be a good spot to tap into an audio ground. Worth a try?
Also I removed the audio fuse but you are correct Joe this powers the mixer and that turns all audio off.

Mich48041 · #27 08-28-2016, 07:07 AM

I suggest that the mic and headphone jacks be wired and grounded per Van's "SkyView-AFTER-08-25-11". Pay particular attention to the ground and shield wiring. The mic Wht/Grn wire is grounded to the AV-50000 Options D-Sub pin 37. And the center terminal of headphone jack is connected to the cable shield which is also connected to the AV-50000 Options D-Sub pin 37 (ground).

rvbuilder2002 · #28 08-28-2016, 10:21 AM

Quote:

Originally Posted by Handclutch

Back in June I was heading off on long trip with my son. I'd noticed the revised plans from Vans calling for isolation of both jacks - my mic jacks were isolated but not the phones - so decided to isolate phones in hope of improving audio. Disaster. No audio at all and we were leaving next morning. Quickly regrounded phones and back in business.

Next step was to instal a PS Engineering intercom. I had used them in previous aircraft and found them to be great. Installation instructions explicitly said both jacks MUST be isolated. Radio guy felt that if we wired PS Eng unit in same way as Flightcom and altered nothing else, everything should work. He was half right. Audio came up strong with phones grounded but no transmit. Contrary to instructions we removed isolating washers from mic jacks and everything is now working perfectly - best intercom/radio function I've had since buying the plane, assisted no doubt by acquisition of new David Clark One X which is a generation ahead of my old David Clark ANR.

Jack

For a specific process to work, all other install requirements have to be met.....
When isolating the mic and headphone jacks, there has to be a ground source for each. If adding insulating washers makes something not work, it is likely an indicator that the installation is not wired an a manner that provides a ground at the intercom and of the wires.

Mich48041 · #29 08-28-2016, 10:46 AM

Quote:

If adding insulating washers makes something not work, it is likely an indicator that the installation is not wired an a manner that provides a ground at the intercom and of the wires.

Agree, that is why I suggested that the mic and headphone jacks be wired and grounded per Van's "SkyView-AFTER-08-25-11". The "Prior" schematic is missing the ground wire on the headphone jack.

D&M Dan · #30 08-30-2016, 02:59 PM

I am now beginning to believe the sound I am hearing is in fact the stall warner. Reminder, my wings are at the airport, so the switch is eliminated as the problem I have checked the stall warner lead to the fuselage harness where it enters the AV5000A and it has continuity. I am wondering if something inside the AV5000A is the issue. Not sure how to check it and have sent a message to Van's tech line.
I believe the sound is generated by the audio mixer inside the AV5000A but I am unwilling to open the box and void any possible warranty, to see if a solder joint is missed or loose.