GTX23 & GSU73 Pin Assignment Discrepancy

[RV7ator]

For our Garmin experts:

The GTX23 manual, (rev. A, C-1) assigns pin 43 of its connector to the RS-232-1 signal ground. The GSU manual (rev. G, D-3) says pin 51 which is "not used" in the GTX manual. Which is correct?

John Siebold

 

[SteinAir]

For our Garmin experts:

The GTX23 manual, (rev. A, C-1) assigns pin 43 of its connector to the RS-232-1 signal ground. The GSU manual (rev. G, D-3) says pin 51 which is "not used" in the GTX manual. Which is correct?

John Siebold

There is a kinda/sorta discrepancy in part of the manual...but...as it says in big capital letter on the top of that page: "This Interface Example Drawing is not Sufficient for Installation of a GTX23ES Unit. Contact a Garmin Avionics Dealer for Complete Installation Information".

Did your dealer not provide you a complete interconnect diagram for your system and avionics that you purchased?

Use pin 43 and you'll be good!

Cheers,
Stein

 

[Auburntsts]

Here's what I did:

GTX 23
Pin 22 RS-232 In -----> GSU 73 P731 Pin 19
Pin 23 RS-232 Out -----> GSU 73 P731 Pin 18
Pin 24 RS-232 #1 In -----> GTN 650 P1001 Pin 8
Pin 43 RS-232 sig gnd -----> GSU 73 P731 Pin 40
Pin 50 RS-232 #1 Sig gnd -> GTN 650 P1001 Pin 46

 

[g3xpert]

For our Garmin experts:

The GTX23 manual, (rev. A, C-1) assigns pin 43 of its connector to the RS-232-1 signal ground. The GSU manual (rev. G, D-3) says pin 51 which is "not used" in the GTX manual. Which is correct?

John Siebold

Hello John,

I checked the PC board schematic, and Stein is correct that GTX23ES pin 43 is a ground and will work fine. GTX23ES pin 51 is also connected to the same ground and will work fine.

We always tell customers that we try to include enough wiring information in the G3X Installation Manual to properly connect these devices to the core G3X components like the GSU73. The transponder connection and configuration information on page D-3 is correct and should be used to connect and configure your GTX23ES transponder.

Let us know if you have additional questions.

Thanks,
Steve

 

[g3xpert]

Hello John,

- Update -

We confirmed with the transponder design team today that the interpretation of the GTX23ES schematic was correct and that both pins 43 and 51 are suitable signal ground pins for this RS-232 port.

Thanks for pointing out this discrepancy. We are going to update both the G3X and GTX23ES installation manuals to remove the confusion.

Since GTX23ES pin 43 has been identified as the signal ground assigned to RS-232 port 1, the G3X manual will be changed to show pin 43 instead of pin 51.

Anyone who has used pin 51 need not change the installation as it will work just as well.

Thanks,
Steve