CharlieWaffles

CharlieWaffles

Well Known Member
I am working my way through some troubleshooting with my new PAR100EX. I am still performing all the checks, but I wanted to ask about a wiring item. I have the PAR100EX and a GTN 750. I have verified I can receive transmissions on both units and have no audio problems. I also believe I can transmit ok on the PAR100 (Configured as com 2). I am waiting to get a receiver so I can verify if I am actually transmitting, but I do get side tone and I can see a RX on the GTN 750 when I transmit on the PAR100EX.

I am following the wiring for the PMA 8000 as it has the same pin outs as the PAR 100EX.

However, when I switch to the GTN750 for the transmit I am not getting any sidetone nor is there a TX shown on the GTN when pressing PTT. I can see the C1 light blinking on the par100ex as I speak when I am pressing the PTT. I booted the GTN750 into setup mode and verified the sidetone setting for the Com is set to the maximum. After double checking my wiring diagram I found a small discrepancy from the Garmin documentation but I am not sure if this could the cause of the problem. I am using the following diagram (Figure E-14)

garmin.png


And I realized that in my wiring plan I didn’t run the Mic Audio In Lo (P1003-20) to a ground lug on the radio. Could this be the cause of my problem? My wiring diagram (at least a portion is below).

mywiring.png
 
Yes, that's most likely the issue. The mike in "lo" probably floats off ground, for ground loop reasons. It should not be connected to the radio ground, but should be connected to ground at the audio panel exactly as shown in the diagram.

It may be that the ground return for the PTT line flows thru this pin (20) too, which is why you see no TX on the transmitter when you try to use it.
 
You need to hook up the lo lines and use shielded wire as shown in the diagram. the low wire runs through the shield and for com 1, terminates at pin 10 on the PAR. Follow the notes on page 37 of your install manual for the par. It details how to run the wires and more importantly, the shields. When a schematic calls a line "lo" it is not synonymous with "ground".
 
I resolved this. I ran the P1003-20 line and also found I had misconnected P1003-11 as P1003-13. Once I moved that and installed the Audio In Lo it worked.
 
Hey Mark, I have the same set up and had similar issue. Side tone on the GTN is controlled on the set up screen. Hold the home button down when you apply power and you will go into the set up screen. Look around there an you can find side tone. This might fix your problem.

Thx
 
And Bill, the Lo in this case is connected to a case ground. J1-10 on the Par100 is for the GTN Audio In for beeps and warnings. The Mic Lo P1003-20 should not be connected to J1-10, the diagram shows Mic Lo P1003-20 connected to the PAr100EX Case Ground.
 
Bill.Peyton said:
You need to hook up the lo lines and use shielded wire as shown in the diagram. the low wire runs through the shield and for com 1, terminates at pin 10 on the PAR. Follow the notes on page 37 of your install manual for the par. It details how to run the wires and more importantly, the shields. When a schematic calls a line "lo" it is not synonymous with "ground".
Click to expand...

That sounds reasonable.... but what is the standard when the radio does not have a MIC LO input pin, like the KY-97A?

http://www.aeroelectric.com/Installation_Data/Bendix-King/KY97A.pdf

It does have a MIC SHIELD, but no LO input...
 
704CH said:
Hey Mark, I have the same set up and had similar issue. Side tone on the GTN is controlled on the set up screen. Hold the home button down when you apply power and you will go into the set up screen. Look around there an you can find side tone. This might fix your problem.

Thx
Click to expand...

Thanks but I had verified that and it was already maxed out. It was indeed a wiring issue in my case - now resolved.
 
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