PTT switch rear stick

7GCBC Sigtronics intercom SPA Have found some info but as of now not for this model, still looking
 
All the -SPA intercoms use the white/blue stripe wire for co pilot PTT.
So one 22-24 ga. wire to white/blue and other wire to a ground (doesn't need to ground to the intercom). Other end to a momentary contact button you're good to go.

Chris
 
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Thanks for the info Chris. Now I just need to remove seats, floor boards, and get behind the panel and start running wire !
 
Once you get the grip off the stick (to install a PTT button) and slide the boot up you can put a couple of small washers on a piece of string and drop it thru the stick...once you have the string thru tie it to the wires and pull 'em thru. That way you don't have to remove the stick!

Chris
 
Thanks Chris. One question, I haven't looked at the back of the intercom yet, but I'm guessing the wires from the rear PTT go to the same terminals as the front PTT ??
 
Ken Kaster said:
Thanks Chris. One question, I haven't looked at the back of the intercom yet, but I'm guessing the wires from the rear PTT go to the same terminals as the front PTT ??
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No. There are no "terminals".
In the wiring harness you need to find the white wire with a blue stripe. That is the wire that will trip the PTT feature for the rear seat. The PTT for the pilot seat is left alone. Also, unless you're an A&P you might want to consult one...just to be legal.
 

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Ken Kaster said:
Chris, I found the blue/white wire coming from the intercom. Where it connects to the harness going to the radio that hole is blank, no connection in the harness, so the blue/white does not continue past the harness connection to the radio. So if I connect to the blue/white wire coming out of the intercom will it somehow feed back to the intercom and make it's way to the radio ??
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It is a Sigtronics SPA but it doesn't have any numbers on it. Two knobs, one volume and the other squelch. I'll see if I can find the paperwork. I checked, it is a SPA 400
 
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Ok. Then if you wire it up like the schematic I posted it'll work great...
The white/blue wire is what tells the intercom to turn on the rear microphone (which is the white/orange wire).

Chris
 
Well, I wired it per our conversation and the Sigtronics schematic which was the same and had no luck. The intercom works as normal the co-p[ilot can talk to the pilot and the co-pilot can hear all what is going on when the pilot is on the radio, everything works as normal. Until the co-pilot activates the PTT switch, then it makes the co-pilot headset go dead. I ran the ground wire to the same location where the pilot PTT and the intercom are grounded and the other wire to the blue/white coming out of the intercom. The only thing I can think of is that the original wire job when the intercom was installed was not right on the wires possible coming from where the headset plugs in or who knows what ?? Any thoughts ??
 
The SPA400 has a little switch that isolates the co pilot from the radio...
it might be in the "iso" position?
That's all I can think of at the moment.
Does the radio show transmit when the PTT is pushed?
Chris
 
The radio shows transmit only for the pilot. Is the iso switch on the front of the intercom, if so, this unit doesn't have one.
 
I'm at a loss as to why it isn't working and I believe my troubleshooting from these many miles away will not be of much more assistance...
The -400 doesn't have an isolate switch, it has an on/off switch...my bad!
Because the radio isn't keying up when you operate the rear PTT I believe that is still the problem. The mike and headphones work for the intercom function so they're wired correctly. The front PTT function works so the radio/intercom interface is good.
I would take a ground wire and ground the white/blue* wire at the intercom case and see if the radio transmit lights up to rule out a bad wire in the connector harness (plastic block).

Past that I'm out of ideas...
* I'm assuming the same white/blue wire goes from the J1/P1 connector to the intercom case. If not, see what color wire is connected to that pin.

Chris
 
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What I did was I removed the blue /white wire out of the connector being there was a blank hole on the other side of the connector. So, the wire was at that point not connected to anything. I connected one of the wires from the PTT co-pilot to that wire and the other to ground. With your headset on when you connect the two wires the headset goes dead, like it is shorted out. Un-connect the wires and it is live again and works normally. So I will connect the blue/white wire to the intercom case as you mentioned and see what I come up with. I just went out and tried to connect the blue/white to the intercom directly, it seems that all screws and switches are insulated from being grounded to the plane, so the only ground is the black wire in the harness. still a big mystery ??
 
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