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Need help with PS Engineering audio panel

sabswbc

Well Known Member
I just completed a panel upgrade on my RV 10 and now I am having problems with my PS Engineering SR audio panel. Everything works fine except the copilots intercom doesn’t transmit out . They can hear but no one can receive. If the PTT is used, they can hear themselves and everyone else can hear also. Here is what is driving me and everyone who has looked at this problem crazy.
I did not replace or change anything having to do with the audio panel or its wiring. In the event something failed in the audio panel itself, I borrowed an exact unit and the problem stayed the same. I replaced the plugs and nothing changed. I ran a new wire with new pins back to the unit and nothing changed.
I made sure tHe shield was grounded and still no voice out for the copilot unless the PTT is activated.
I can’t think of anything else to do except learn sign language to communicate with the copilot. All ideas are welcome please.
Sam Butler
817-821-7971
 
Can you be more specific? The PS web site doesn’t show any ‘SR’ audio panel. There is a xxxSR music system but it does not have an intercom system.
.???
 
Some intercoms have a "push to talk" mode (not to be confused with push to transmit). Some helicopter people still like this as the squelch can be a challenge on VOX systems with the doors off.
 
Ps Engineering made a model SR that had XM radio. They were very surprised that we had two units on the field. We have tried all the modes and many different headsets. There only three wires to pins 32, 33, and 34. Doesn’t make much since.
 
What radio are you trying to transmit on?

Some radios, like the iCom A210/A220 have a quirky keyline setup that can be quite frustrating.
 
Wild guesses:
1. You actually have a PS 8000SR
2. Your copilot position is using an older portable type PTT switch held on with velcro, where the switch comes with a plug which goes into the aircraft mike jack, and also comes with a jack, into which you plug the mike plug. Some of these switched the ground lead, meaning it wouldn’t work unless the switch was pushed.
3. There must be more than 3 wires going into the audio panel.
 
So on the J2 connector of the unit you have:

Pin 32 = Copilot Mic Audio (jack ring) - EDITED
Pin 33 = Copilot Mic PTT (jack tip) - EDITED
Pin 34 = Copilot Mic Lo (jack barrel)

The wiring for the copilot PTT should be conventional. In other words the PTT switch should be connected to wires attached to pins 33 and 34 so that the PTT is pressed it grounds pin 33 to pin 34, or the ring to tip (edited) on the jack, respectively. It is very common for the PTT wire to soldered to the jack terminals. It could also be spliced into the 33/34 wires at the audio panel.

Some other audio panels or intercoms will have a dedicated PTT pin that eliminates the conventional jack grounding. In other words the PTT switch is wired directly to one pin on the audio panel on one side of the PTT switch and then to airframe ground on the other side of the PTT. That bypasses the traditional jack grounding wiring scheme. In this type of audio panel the PTT wire is simply a signal wire that when grounded tells the audio panel to key the radio for the proper mic internally via a digital relay. So if you are changing out the audio panel from another type then make sure the microphone PTT circuit is wired properly for the PMA8000SR.

The wiring to the microphone jack should be via 3-conductor shielded wire with the shielding drained at the back of the audio panel or audio ground. The jack should be isolated from localized ground with insulating plastic or phenolic washers (one shoulder washer on the back, one flat washer on the nut side).
 

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  • Copilot PTT Jack PMA8000-SR-IM.jpg
    Copilot PTT Jack PMA8000-SR-IM.jpg
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WHen the co-pilot presses the PTT, do only the other crew hear the audio or does it also transmit on the radio?

If you have a conventionally wired jack, with both PTT and Mic lo connections, via a three conductor receptacle, I am guessing that you got the PTT and mic lo connections swapped. In order to transmit, the panel needs a full circuit from Mic Hi through the mic itself and back to a ground (usually Mic Lo, but any frame ground will work). If the mic lo and PTT are swapped at the receptacle, then the co-pilot transmissions will only be heard when the PTT is depressed, as this is the only time that the mic circuit is completed back to a ground (PTT at the panel is a positive source, not a ground source). If the PTT is wired into the mic circuit, it would make sense that it doesn't activate due to being wired back to the hot side instead of ground.

Put an ohm meter lead in each of the three prongs of the receptacle and confirm which pins they go to. Then confirm connectivity via the manual. When viewing the plug, the tip is the PTT, the Ring or middle section is the Mic hi and the sleeve or rear most section is the Mic Lo.


Larry
 
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Yep. Good catch. Got those two backwards. That wasn't very helpful interjecting the wrong prongs. I will go fix it to avoid confusion.

Jim
 
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