Audio connections between Garmin GNC 255A and PS Engineering PMA4000 audio panel


Kevin Short
 

 Ok group...  Please Help! .. am near my wits end.  

Setup:     My GNC 255A Nav/Com radio is connected thru my PMA 4000 audio panel.    I also have an Icom A200 .. but it works great.  

Comm Problem: went transmitting with the GNC 255A  there is no audio thru my headset... IE  I do not hear myself speaking thru the intercom like I do with the ICOM.  I do get a TX indication on the GNC-255A face but..... Shouldn't I get audio thru my headset as I transmit?   Y or N.?     If yes... please read on.. Now It will help me tremendously if you base your responses on the following: .( they can be downloaded easily) 

1.  Page D-4 of the Garmin GNC 255A installation  manual .  (GTR/GNC Typical installation) 
2.  Appendix B of the PMA 4000 installation manual  (Unit Connector wiring)  

Notice:  Each diagram has numbered connection depictions from their specfic unit to the generic unit (non-numbered). ..  (I get this ...they cant show every possible option audio panel option)   

Here is how I have the comm pins connected currently:   5 silly little wires....

 
GNC 255A                                        PMA 4000 
P2001 connection                           Connection                       


Pin 7 (Com Audio Hi) .......--> ..........Pin 19 (Com 1 Audio Hi)  on the TOP CONNECTOR (female) 
Pin 18 (Com Audio Lo) .....-->...........Pin  7  (Com 1 Audio Lo)  On the TOP  Connector  ( female) 

Pin  20 (Mic Audio In Lo) .....-->........Pin  9  (Com 1 Mic Audio Lo) ON THE PMA BOTTOM Connector

Pin 5  (Com Mic1 Audio IN Hi) ..->...Pin 21 (Com 1 Mic Audio OUT Hi) ON THE PMA BOTTOM Connector
Pin 11 (Com Mic 1 Key)    ........-->...Pin 22 (Com 1 Mic Key Out )  ON THE PMA BOTTOM Connector

Note :  The three wires  on the PMA 4000 Pins 9, 21, 22 are in a single shielded bundle labeled  C1 MIC...
             The two wires  on the PMA 40000 Pins 7, 19  are in a single shielded bundle  labeled  C1 PH.....


Please focus on the GNC 255A  Pin 20  "Mic Audio In Lo"   and the PMA 4000  Pin 9 " Com 1 Mic Audio Lo"     ( I have been told  "Audio lo"  equates to "GROUND" )    
The folks at PS Engineering said to connect  GNC 255A Pin 20  to PMA 4000 Pin 9   ... I guess because they both refer to the  "Mic Audio Lo"  ie Ground...  but in doing so I get NO headset audio when I transmit.  

 My gut tells me the  GNC 255A pin  20 should really be connected to PMA 4000 Pin 7  ..(yellow highlighted) .. this is shown on GNC install Page D-4 in the middle of the sheet near the generic audio panel .. However the folks at PS Engineering said to connect  GNC 255A Pin 20  to PMA 4000 Pin 9 ?

Now if I go back and connect  GNC 255A Pin 20   to   PMA 4000 Pin 7    What should be done with PMA 4000 Pin 9? ...  connect it to ground?   leave it wagging?   Yank it out  :-) ? 

Thanks in advance for compassionate responses... I am sure there are some who have solved this issue...


Kevin S  N548KD  52 hours+ 

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