SV-Com-C25 Receiving but not transmitting

[Darrin Towers]

The last few days I have been installing and setting up everything, today I wired up the the push to talk button on the stick. the radio receives very clear picks up traffic miles away and works with Skyview. But after wiring up my PTT button I set my hand held and the com to 123.45 and pressed the button. The Transmit light on the intercom changes but I get nothing on the hand held. I can hear other traffic on that channel, I can hear myself in the head phones through the intercom. Just not transmitting.

 

[jakej]

Darrin - without seeing how you physically wired it it’s hard to diagnose however I’d double check that the mic HI wire is connected to the jack correctly. Can you post a picture of the mic jack wiring ?

 

[Darrin Towers]

Jake, Here is a photo, the wiring harness was custom made purchased through Aircraft Spruce, Im not sure if it was made at Dynon or elsewhere.

 

[Darrin Towers]

I wonder if it could be the PTT that goes from the intercom to the SV COM is the problem

 

[djones]

Darrin,
Make sure which radio you actually have. The diagrams above are for two completely different radios. The SV-COM-C25 and the SV-COM-X25
The C25 uses the older Dynon 425 radio and the X25 is the Dynon T25 radio. The 425 has a 15 pin connector and the T25 has a 25 pin connector.

 

[Darrin Towers]

Darrin,
Make sure which radio you actually have. The diagrams above are for two completely different radio's. The SV-COM-C25 and the SV-COM-X25
The C25 uses the older Dynon 425 radio and the X25 is the Dynon T25 radio. The 425 has a 15 pin connector and the T25 has a 25 pin connector.

I do have the T25 and have the correct drawing printed off with PTT in going to pin 15, Mic in going to pin 23 and PTT ground going to Pin 9. I'm wishing that the custom harness I bought through Aircraft spruce would of had a wiring diagram. I'm hoping that it is something simple like a pin pulled loose from the socket. I know everything going to the intercom is good and working.
After I verify the correct pinout, Is it possible to check continuity with the system powered down? I would like to verify that the when the PPT button is pushed that there is continuity between pins 15 and pin 9, I also would like to test continuity from the mic jack to pin 23, but I'm thinking that the intercom would have to be powered up for the connections to be made. I could pull the breakers on everything except the intercom but concerned about testing with anything powered.

 

[jakej]

Darrin, trust but verify - I have seen examples of pre made wiring looms not done properly, & by well known companies - maybe they don't pay well enough &/or the looms are not bussed out before shipping. Looks like that's your job now .

 

[Darrin Towers]

Had Time to work on it this afternoon and found the problem. I'm not sure what the plan was with the way the wiring harness was wired but coming out of the 25 d-sub connected to the T25 on pin 15 was a wire that had com PPT that was then spliced 3 ways into a wire that was labeled INTERLOCK and a third wire not labeled. On pin 18 was another wire labeled INTERLOCK. I had those capped off with shrink tubing and coming out of the intercom on pin 12 there was another wire with no label on it so I had it capped off with shrink tubing thinking it was for the interlock also. so I clipped the splice off the one from pin 15 on the com and put a new d-sub pin on it and plugged it directly into pin 12 on the intercom and it worked.