intercom not working

cannot xmit when intercomm is in ICS(all)
The saga continues. I can xmit only in isolate on intercomm. talked to flightcom
they said that if pin 7&8 were swapped that would be the case. If pins are correct then intercomm is bad. I checked those pins and they are correct So I ordered a new intercomm from vans and installed it. Still has the same problem!!!!! Has to be wiring or circuit brd. vans will not give out pinouts and color code.Have reprogramed the radio as vans directed . don't know where to go from here.

mangan01 said:

cannot xmit when intercomm is in ICS(all)
The saga continues. I can xmit only in isolate on intercomm. talked to flightcom
they said that if pin 7&8 were swapped that would be the case. If pins are correct then intercomm is bad. I checked those pins and they are correct So I ordered a new intercomm from vans and installed it. Still has the same problem!!!!! Has to be wiring or circuit brd. vans will not give out pinouts and color code.Have reprogramed the radio as vans directed . don't know where to go from here.

Click to expand...

How about if we start with you trying to be more specific in detail as to what you are describing.

Example... you say you "can't transmit" with the switch in ICS.
Does that mean the radio doesn't show the Xmit indicator, or just that no one can hear your transmission?
If it means no one can hear you (meaning you are transmitting a carrier only, but when in Isolate you can transmit.... meaning someone with a receiver can hear you, then their probably is a wiring mix up.



Use an ohm meter/continuity tester to verify that when you push and release the pilot PTT switch (switch on the left stick), pin # 7 on the Dsub connector that plugs into the back of the intercom switches between shorted to ground and open. Do the same with the copilot side PTT switch (right stick) while checking pin # 8. If they are not working correctly, see if pushing the opposite PTT switch produces a change on your meter/checker. If all is well, move on to checking the mic jacks.

Check continuity between the shorter of the two tangs on the pilot mic jack (the one that contacts the ring position on the mic plug), and pin 2 of the intercom Dsub connector.
Do the same with the copilot mic jack and pin # 3 on the Dsub connector.

If your radio is always switching into transmit (and sending out a carrier) when you push a PTT switch, but you can't always be heard, the only likely cause is a wiring problem with either the PTT switches, or the mic jacks.

The checks described above should show you which it is.

(another thought.... in a previous post you said that when transmitting, all anyone could hear was engine noise. Did you have a second head set plugged in when that was happening?)

A couple of questions:

1. Why have you started a new thread on this? It is helpful to have all the history in one place.

2. In your previous post on this topic, you thanked other builders for sending you the wiring diagram. Since you apparently have the diagram, have you traced out and double checked all the wiring?

3. How much electronics background do you have? If you're not experienced in this area it might be very helpful to get some assistance. Is there a EAA chapter in your area, that might have a tech counselor who has some experience in audio circuits?

4. What brand/model headsets are you using? Have you tried a different brand to eliminate that possibility?

...also... Scott (RVBUILDER2002) makes a good point. If we are to try and help you through this we need VERY specific information. For example, there is a big difference between not transmitting at all, or transmitting a carrier with no or garbled audio.

John

It is highly unlikely that the problem is within the Control Board. The headset and PTT wiring goes directly to the intercom. Since the intercom has been replaced, that is no longer suspect. That leaves the headsets and the aircraft wiring. Since the headsets seem to work OK when the intercom switch is in the isolate position, I suspect the aircraft wiring, most likely at the intercom D-Sub connector. The embossed pin numbers are so small that only a little kid can read them. And sometimes the numbers are located between two pins, so it is easy to get them mixed up (maybe 6 & 7). The fact that engine noise is being transmitted tells me that pilot and copilot wires are crossed.
When it is not working, have you tried reaching over and pressing the copilot's PTT to see what happens?
Joe Gores

When I say I can't xmit in ICS I mean no one can hear me,I have no range. If a radio is within 5 feet they can hear me in ICS, any further out and I become inaudible.
The radio is working fine and I have TX from both sticks PTT. I have a David Clark and a Pilot headsets same problem with only 1 headset installed. The schematics that I received did not include the com plug going to the circuit brd. and like I said I am loud and clear in isolate, so that says that the coax and antenna are good. the intercom function seems to work sometime and then can't get it to work at other times with the same headsets.

A bad connection on one of the wires supplying power or ground to the intercom could cause the symptoms that you describe.
Intercom pin 1 is the ground wire and it is connected to control board pin 9.
Intercom pin 20 gets 12vdc from control board pin 1.
An intermittent problem is hard to solve because it might be working OK at the instant that you test it.
Check all of the ground wires and splices. Tug gently on the wires to make sure that they are securely connected. A suspect crimp connection could also be soldered as long as the resulting stiff wire is well supported to prevent breaking from vibration.
Sometimes a pin in a D-Sub connector is not making good connection. Make sure that that the pins are locked in place and make good contact.
Joe Gores

My two cents - -

I had a similar problem, and it turned out to be the ant connection itself. Had to take it apart and re-crimp it. It was doing just what you are describing. If you have a helper, take the inspection plate off and slightly move the wire back and forth slowly, and see if that changes it some. That is how I found mine finally.

John Bender

mangan01 said:

The schematics that I received did not include the com plug going to the circuit brd.

Click to expand...

The schematics you received do have the control board connections on them. You need to spend a little more time learning how to read them.

John Bender,
The fact that the transmission can be heard up to 5 feet but no farther sure sounds like an antenna problem, doesn't it. It could be a coincidence that the antenna works OK when the intercom happens to be in isolate. Or there could be two problems to confuse us troubleshooters.
Joe Gores

Yes Joe - -

I have been working on other projects and did not pay close attention to this thread. After I read it, I realized it was exactly what I ran into. The ant cable ends were not crimped as well as needed in some cases. I could move mine around and it would work better at times, coming in and out. I might also add, fixing it is not fun either. Had to lay on my back underneath and re-do the crimp. Otherwise, you'd have to try to get the cable back up inside to work on.

John Bender

Problem. Pilot can hear transmissions from other aircraft; but, pilot and co-pilot cannot transmit to other aircraft or to each other. When either the pilot or co-pilot push the PTT, on the top of the stick, the red T on the Garmin SL-40 lights up.

Equipment. Have the Dynon Skyview, Flightcom 403, Garmin SL-40; all installed with conversion wiring.

Tests.

The wiring connection to the external antenna was disconnected and inspected. Wiring appeared to be good. Reconnected the wiring to the antenna.

PTT.
Did a continuity test between pin #7 (on the Dsub connector on the back of the Flightcom 403) and ground ? when the pilot PTT was pushed there was continuity.

Did a continuity test between pin #6 and ground ? when the co-pilot PTT was pushed there was continuity.

The electrical schematic shows I should get continuity as it tested.

Mic Jacks.
Did a continuity test between the shorter tang on the pilot mic jack and pin #2 (on the Dsub connector on the back of the Flightcom 403) ? did not get continuity. On pin #3 (co-pilot mic), did get continuity. Per the electrical schematic, I should get continuity on pin #2 (pilot mic).

Did a continuity test between the shorter tang on the co-pilot mic jack and pin #3 (on the Dsub connector on the back of the Flightcom 403) ? did not get continuity. On pin #12 (co-pilot headphone), did get continuity. Per the electrical schematic, I should get continuity on pin #3 (co-pilot mic).

So, what should I do from here?

Remove the wires that connect to the wrong pins and rewire according to the schematic. This is how my D-180 system intercom is wired. Yours is likely the same.

I moved pin #3 to pin position #2.

And, moved pin#12 to pin position #3.

And, moved the original pin#2 to pin position #12.

Both the pilot and co-pilot can now receive and transmit.

But, the pilot and co-pilot can not talk with each other. Yes, the Flightcom 403 is in the ICS position.

How do I go about testing the continuity for the wiring in the intercom? rv2002 gave a good description of how to test the PTT and the mic plugs; but, I can not find a description of how to test the intercom. I have tried matching the wire colors to the schematic, but have had no luck.

Others of us with the conversion harnesses have had difficulty. In my plane the ISOLATE function on the 403 cuts out the pilot, not the co-pilot. But other stuff works more or less OK. There are some volume issues with the Skyview voice alerts. There are a couple of other threads on this.

It is VERY difficult to adjust the pots on the AV5000 once installed - to even know if the screwdriver is engaging. (Yes, I've cut the screwdriver.) I intend to delve back into the wiring in April at the annual. I think it may be necessary to unscrew the AV5000 and lift it a bit to get eyeballs on the pot screws.

I am also considering totally taking the AV5000 out of the audio intercom equation entirely - simply pulling all the audio wires going into it and wiring the headsets, radio and Skyview audio directly to the intercom. I got the first AV5000 delivered. I don't fully trust it because when I added the Dynon ADSB box, it was not plug-and-play. The 4 wires needed by the ADSB box are power, ground, and a serial pair. The power and ground worked, but the serial wires did NOT make their way from the ADSB DB connector on the AV5000 to any of the serial pins on the 37-pin Skyview connector. I had to take them directly into the 37 pin connector.

There are also issues with the 403 intercom/ conversion harnesses combination with mixing stereo and mono headsets. The QT Halos I got work great in other planes but not (YET) in my RV12 - (no audio and occasional horribly loud squeals). All of which I hope to address in April...

It has been a bit frustrating... but all works well with my existing mono headsets as long as I don't use the ISOLATE. Oh, I've never used the music input at all, will probably disconnect it too.

So - keep working and document what you find! Thanks!

Bill - March 2015.

I am sure that you have already adjusted the Flightcom 403.squelch and volume. There are also some dip switch settings. What about the headsets? Are they the same brand? Are they both mono or both stereo? They should both be the same.

When I moved the wiring, so the pilot and co-pilot can both transmit and receive transmissions, I was able to move the Flightcom 403 squelch and volume to the recommended 3 and 11 o?clock positions without getting a high pitched squeal.

Have not looked at the dip switch settings on the AV50000A.

Tried all different combinations of headsets (stereo stereo, mono stereo, mono mono, and different brands) ? thanks to some friends. Did not change anything. Plan on using two Lightspeed Zulu headsets.

Looked at the Flightcom 403 Dsub pilot and co-pilot headphone wiring schematic (there are four wires) until my head hurt. Would like to find a way to check the continuity on these wires; but, I am mystified on how to connect the multimeter from the Dsub wires to ???? so I can get the intercom working.

When I mentioned DIP switches, I was talking about those inside of the Flightcom. But chances are that those switches are not causing the problem. It will not hurt to check them though. Default is all 4 switches shut off.
Have you measured the voltage between Flightcom pins 1 & 20?
Have you tried turning the Flightcom squelch fully counter-clockwise and the Flightcom volume fully clockwise? Are the headset mics close enough to kiss?
I could be wrong, but it seems to me that if both the pilot and copilot can transmit and receive on the com radio, then the aircraft is wired correctly and there is no need to check continuity. Call Flightcom 800-432-4342 or 503-684-8229 and ask their advice.

If you do not hear the squelch break as the the intercom squelch knob is turned, then I think the problem is inside of the Flightcom 403.

Continuity check:
Flightcom D-Sub Pin 1 - - - - - - - Sleeve of Pilot Headphone Jack
Flightcom D-Sub Pin 14 - - - - - - Ring of Pilot Headphone Jack
Flightcom D-Sub Pin 13 - - - - - - Tip of Pilot Headphone Jack

Flightcom D-Sub Pin 1 - - - - - - - Sleeve of Copilot Headphone Jack
Flightcom D-Sub Pin 12 - - - - - - Ring of Copilot Headphone Jack
Flightcom D-Sub Pin 11 - - - - - - Tip of Copilot Headphone Jack

The easy way to check continuity of a headphone jack is to insert a 1/4" plug into the jack and then connect ohmmeter to the plug terminals.
HEADPHNE JACK DRAWING

Bill, check your PM. Scott