Built-in Intercom

[FredMa]

your description is very hard to follow. I am assuming you are saying that your PTT switch is hard wired to the intercom utilizing the same pins as your MIC jack input. I don't know what you are describing as a "joint". If you mean a splice to extend the 3 wires from your PTT so they will reach your intercom, that would make sense but I am not sure that is what you mean. You need a wiring diagram for your PTT switch. I believe they come with a new ptt switch and you need the wiring diagram of your intercom. I have one for the PM1000 since that is what I have. You didn't say what you have. The color coding that telex chose is not going to match a field fabricated extension to connnect your PTT to the intercom. you simply have to identiy which wire is which and wire it to the appropriate input of the intercom. The 3 wires we are talking about are pilot mic input, pilot ground and pilot PTT. The PM100 would be wired -pilot mic input to pin 23, pilot ground to pin 11 and pilot PTT to pin 24.

[PaddyM]

Thanks Fred for the reply.
What I call a"joint" I guess you call a "splice" -- certainly we are talking about the same thing.-- a junction place where 2 wires are cut and wrapped together adding a length of wire to continue along the circuit.
Ideally soldered and heat shrink wrapped for further protection against moisture.
Agreed, my description is a little hard to follow, but I think you have it.

I was hoping someone out there may have a wiring diagram for the Telex pt300 that they could scan and send along.

Searching through my airplane stuff I found another pt300 with the jack and plug still in place.

Reading George's application again I understand what he did and I wonder if I could try the same thing at least for a test.
That is insert the male jack from David Clark headset into pt300 plug then the remaining jack into my transmit panel mounted jack.
This may at least identify some issues for me, just not sure if that will connect me to my intercom etc.
I will report back!
Thanks again,
Pat

[KS170A]

What radio and intercom do you have? Does it normally have a "transmit" indication when you hold the PTT down? If so, is it doing it now? Is your comm transmitting anything (as in carrier only, no voice)? I have a GNC250XL and had a SPA400 integrated with it. Sigtronics had this helpful diagram; perhaps it may help you visualize how your wiring should be?

[PaddyM]

I have a Siogtronics intercom as well.
Last communication with tower he said he could hear the carrier , but no voice.
We tried again yesterday with my wife using a handheld--I could hear her, she could hear clicking, but no transmission from me in ac.
Thanks for the attachment-- I will study it.

[PaddyM]

Still no joy-- the wiring diagram was helpful, so I'll try to trace all wires as maybe there remains a connection broken somewhere.

[KS170A]

Since the radio is transmitting the carrier, might be an issue with the mic jack/wiring. Is there one for the copilot side? If so, what happens if that one is pushed and broadcast attempted? Don't overlook grounding wires and shielding. Many times those shields come in contact with something they shouldn't and cause all sorts of headaches.

[FredMa]

Paddy, are you using a known good headset? if so consider this, the PTT switch you found and plugged into the mic jack may also be bad. Unless you troubleshoot with known good components, you will likely end up spinning your wheels. A known good ptt switch plugged in to your mic jack would tell you the problem is not your original PTT as you have provided the same switch input from a parallel circuit to the intercom with the same results. the next step I would take (If I had the correct wiring diagrams) would be to connect a PTT directly to the mic inputs of your radio. If that worked, the problem would be with your intercom or associated wiring, If not the problem would most likely be your radio.

[blueldr]

In days of old when pilots were bold, I went through about three or four el cheapo, Velcro strap-on, PTT switches. I grew wise with age and I still had my own teeth so I bit the bullet and sprung for a Telex PTT switch that also happened to strap on with Velcro. Looked just like the el cheapos. Lasted almost as long. When I took it apart, it was pretty obviously just another of the exact same Taiwanese switch with the Telex name and price. I finally got into micro switches from Radio Shack and never had another failure.

[PaddyM]

Great ideas guys Thanks,
Now to answer a couple of your questions... Head set a David Clark-- no broken / loose wires etc as I take care of them and never any previous issues.
The "found" ptt is also a Telex PT-300-- same as old one installed on pilots yoke
I just put my multimeter leads on the ptt and did get needle deflection each time I pushed the talk button-- so that appears to be working.
As I stated I could receive but not tx, so with all the suggestions provided, I'm going to start with known operable equipment, and begin with the mike jack(s) then look further toward radio tx contacts and still further at the antenna connections.
We will get there!
Pat

p.s.
again if anyone has a wiring diagram for the Telex PT-300 I would appreciate a copy.

[GAHorn]

There appears to be two threads on this subject. I'm not sure how that helps direct the discussion, so I may merge them.
Anyway, this link might help you troubleshoot the problem. Although it isn't the same radio / intercom setup you have, it should illustrate the various methods of wiring. http://www.aerialpursuits.com/comms/pttccts.htm

[PaddyM]

Got it George Thanks.
These should help.
Pat