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Pilot MIC wiring TX issue

WingnutWick

Well Known Member
Hello all,

Trying to see if anyone has any ideas to narrow my efforts down before I go crazy chasing wires. I was recently working behind a segment of the panel to install a push button starter and when everything went back together I realized the PTT no longer worked. I checked out the jack and noticed the wires (circled in red) had been pulled out. Easy fix I figured so I soldered it back on and it still wont transmit. The only way I can get it to (at least have the TX show up when I hit the PTT) is when I take off the rubber grommet and the barrel touches the panel metal.

What am I missing? Is this segment connected to a ground or something and perhaps I pulled the other end off as well. The other end is buried deep in the panel and so I wanted to see if I was mussing something on the jack end before deep diving.

Thanks all!

Charles
 

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It appears to my eyes that there are two wires circled in red, attached to the "tip" connection, which is the PTT connection. But unless you actually use a PTT plugged into that jack, it looks like it's just a "pass thru", e.g., one wire coming from somewhere (stick PTT switch?) and the other wire then going to the audio panel or directly to the com PTT input. You obviously hit it hard enough to pull it off the solder. I'd suggest tracing it back towards the stick PTT, looking for somewhere you pulled it loose at the other end (or even broke the wire). An ohmmeter can be a big help here.
 
The thing is when I have the barrel grounded the button on the stick works so I don't think it came loose from the stick. But I am pretty sure the barrel is not supposed to be grounded (hence the rubber grommet and the composite washer on either side). Perhaps these two go to a ground?

It appears to my eyes that there are two wires circled in red, attached to the "tip" connection, which is the PTT connection. But unless you actually use a PTT plugged into that jack, it looks like it's just a "pass thru", e.g., one wire coming from somewhere (stick PTT switch?) and the other wire then going to the audio panel or directly to the com PTT input. You obviously hit it hard enough to pull it off the solder. I'd suggest tracing it back towards the stick PTT, looking for somewhere you pulled it loose at the other end (or even broke the wire). An ohmmeter can be a big help here.
 
Reinstall the jack. Short the tip to ground to ground to confirm a TX or not. If it does TX, the problem is between the tip and ground (PPT switch or related wiring.
 
It sounds like the ground wire to the PTT has come loose at the grounds connector, or the wire is broken. Assuming that there is (normally) a ground terminal block then it should be apparent by looking at it whether a wire has pulled off. The problem will likely be at the other end of one of those two fine wires that you soldered back onto the mic jack.
 
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The jack is normally isolated so it has a single point ground, for noise reasons. Put an ohmeter on the terminal with the two white-blue stripe wires, the other side to the airframe. If it’s not a short you found your problem. One of those wires should go to the single point ground buss, probably near the audio panel or radio.
 
Wiring

A suggestion: install shrink tubing on ALL soldered connections as it provides stress relief to the connection. Tefzel wire (like the teflon wire I learned back in the early space contracting days also will allow solder to "wick" up inside the insulation which makes the joint stiff or brittle) A good way to mitigate this is to heat sink with a pair of tweezers at the insulation ( a little piece of sponge attached to the tweezers dipped in isopropel alcohol keeps the insulation cool.
Just a suggestion if you solder a little long.
Definitely use the shrink tubing...
from
An ol NASA certified technician from Honeywell...:D
 
Thanks!

Thanks all,

I temp fixed it by grounding the jack to the panel by removing the rubber grommet on the back. My understanding is that the only reason for not doing this is noise purposes. If I understand correctly I believe the problem lies on the other end of these wires. Was probably pulled out at the same time the jack side was. I will hunt down the loose connection and fix it properly - to include shrink wrapping the joints :)

Thanks for the soldering tips. Soldering well seems to be an unlearnable skill for me.
 
Checked out the other wires and they look fine, kind of stumped so I'm just going to go with grounding the jack to the panel as it seems to work 4.0 that way.
 
Checked out the other wires and they look fine, kind of stumped so I'm just going to go with grounding the jack to the panel as it seems to work 4.0 that way.

It’s EAB, your choice. Personally leaving a known broken wire or connection somewhere behind the panel would drive me crazy. Also bare in mind that isolating the jack from the airframe is done to prevent ground loop noise. This often won’t show up until sometime later down the road, as lap joints oxidize and gain a tiny amount of electrical resistance.
 
You don't by any chance have an iCom A2XX radio do you? That radio requires a very low potential on the ground leg of the PTT circuit. Some intercoms have a few milivolts potential on the PTT circuit that can mess up PTT under some conditions. And, its not consistent in every installation.
 
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