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01-23-2017, 11:47 AM
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Join Date: May 2015
Location: Crittenden, ky
Posts: 194
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Putting together a G3X system
I'm in the early stage of (paper) wiring up my G3X system and would like to open this up as a thread - I invite advice and critiques, and I'll share the information as I get answers from the G3Xperts.
My planned system:
GDU 460 - 1
G5 - 2
GTR 20 - 1
GEA 24 engine interface
GAD 29 acars / data concentrator
GMA 240 audio panel
GMC 307 autopilot panel
GSA 28 - 2 servos
GSU 25 adhars
GMU
GNC 255A
GTN 625
My preliminary interconnect drawing (based on the Garmin basic drawing):
I just sent an email to g3xperts@garmin.com with a question about the connections between the GDU and the GTN nav. I asked about the diagram on page 24-25 of the G3X manual that shows two RS232 connections to two separate GDUs. One is the MXMAP format channel, and the other is a Connext channel. I asked if I need both channels to my single GDU. If it requires two channels, I am out of serial channels to the GDU which has 5 max.
I have also asked about routing the GNC 255 to the GAD 29 instead of using a serial channel to the GDU. I'll post the answers I get as I get them.
I find this stuff fascinating, but it do make your head buzz once in a while and I can see why a lot of folks go to Stein and others to have it done. 
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01-23-2017, 12:26 PM
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Join Date: Jul 2014
Location: Madison, WI
Posts: 685
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Don't forget the redundant rs232 from he gea24 to the gdu.
__________________
---
RV-9A - started 01/2015, completed 07/19/2018, 500hrs 03/14/2020
RV-10 - started 04/2020
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01-23-2017, 12:34 PM
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Join Date: Aug 2007
Location: Spring, TX
Posts: 449
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Just wondering why you went with the GTN625 and a GNC-255A when a GTN-650 would do all the same with less room and wiring and I believe less cost too.
Thanks,
Jay
__________________
Jay
RV-9A
Empennage complete.
Wings complete.
Fuselage in progress
Wiring in progress
2020 Donation made!
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01-23-2017, 05:29 PM
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Join Date: May 2015
Location: Crittenden, ky
Posts: 194
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Quote:
Originally Posted by pilot2512
Just wondering why you went with the GTN625 and a GNC-255A when a GTN-650 would do all the same with less room and wiring and I believe less cost too.
Thanks,
Jay
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Hi Jay, the deal at the time - the gtn 625 was much cheaper when bought with a g3x system, and no discount was offered on a 650 or 750. I think I would have spent close to $2000 more for a 650. Yes it would be easier, but hey, 2 grand, and if something breaks I'll still have a nav in the plane while the other box gets fixed.
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01-23-2017, 05:53 PM
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Join Date: May 2015
Location: Crittenden, ky
Posts: 194
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Quote:
Originally Posted by gfb
Don't forget the redundant rs232 from he gea24 to the gdu.
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Thanks, I did overlook that one. Hope I have enough rs232 ports.
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01-24-2017, 04:45 AM
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Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,885
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Quote:
Originally Posted by SgtZim
I just sent an email to g3xperts@garmin.com with a question about the connections between the GDU and the GTN nav. I asked about the diagram on page 24-25 of the G3X manual that shows two RS232 connections to two separate GDUs. One is the MXMAP format channel, and the other is a Connext channel. I asked if I need both channels to my single GDU. If it requires two channels, I am out of serial channels to the GDU which has 5 max.
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Hello SgtZim,
Nice system you are putting together.
Just a quick note to mention that your GDU 460 display has 6 serial ports, not 5.
As shown on page 23-19 of the Rev. AA G3X Installation Manual, the 6th serial port is on 9 pin connector P4601. This serial port is designed to be used for the backup data path for your GSU25 #1 and is permanently programmed for the "Garmin Instrument Data" format for this purpose.
If you are running low on serial ports, you can also consider only connecting the GMC 307 autopilot control panel to the roll servo and not to the display. There isn't a lot of benefit to connecting the GMC 307 to the display. The connection to the roll servo is the important connection and the only one that matters if your GDU 460 becomes unavailable and you need to operate your autopilot using the G5 and the GMC 307.
One additional comment. We noticed you had a GMA 240 audio panel in your list. This is a great audio panel, but you might also consider the new GMA 245 if you have not yet purchased the GMA 240.
Thanks,
Steve
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
Last edited by g3xpert : 01-24-2017 at 05:00 AM.
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01-24-2017, 06:21 AM
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Join Date: Jan 2005
Location: Cincinnati, Ohio
Posts: 1,060
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Hey Steve,
What is the benefit to connecting the 307 to the display. I've been doing that, but would love to get rid of unnecessary connections.
__________________
Jon Thocker
Habitual Offender
RV4, RV4, RV6A, RV8, RV8, RV8,RV8, RV8, RV8, RV12
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01-24-2017, 06:47 AM
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Join Date: Sep 2010
Location: Olathe, KS
Posts: 2,885
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Quote:
Originally Posted by jthocker
Hey Steve,
What is the benefit to connecting the 307 to the display. I've been doing that, but would love to get rid of unnecessary connections.
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Hello Jon,
It is mostly just another data path. If you were to lose the RS-232 connection from the GMC 307 to the roll servo, you could still use the GMC 307 if you have the backup data path to the display. The GDU 4XX touch screen autopilot controller is, of course, a backup against loss of the GMC 307 making it less important to have a backup RS-232 data path.
Thanks,
Steve
__________________
Garmin G3X Support
g3xpert@garmin.com
1-866-854-8433 - 7 to 7 Central Time M to F
Please email us for support instead of using Private Messaging due to the limitations of the latter.
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01-24-2017, 08:57 AM
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Join Date: Jan 2005
Location: Cincinnati, Ohio
Posts: 1,060
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Quote:
Originally Posted by g3xpert
Hello Jon,
It is mostly just another data path. If you were to lose the RS-232 connection from the GMC 307 to the roll servo, you could still use the GMC 307 if you have the backup data path to the display. The GDU 4XX touch screen autopilot controller is, of course, a backup against loss of the GMC 307 making it less important to have a backup RS-232 data path.
Thanks,
Steve
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Thanks Steve!
__________________
Jon Thocker
Habitual Offender
RV4, RV4, RV6A, RV8, RV8, RV8,RV8, RV8, RV8, RV12
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01-24-2017, 09:40 AM
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Join Date: May 2015
Location: Crittenden, ky
Posts: 194
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Quote:
Originally Posted by g3xpert
Hello SgtZim,
Nice system you are putting together.
Just a quick note to mention that your GDU 460 display has 6 serial ports, not 5.
As shown on page 23-19 of the Rev. AA G3X Installation Manual, the 6th serial port is on 9 pin connector P4601. This serial port is designed to be used for the backup data path for your GSU25 #1 and is permanently programmed for the "Garmin Instrument Data" format for this purpose.
If you are running low on serial ports, you can also consider only connecting the GMC 307 autopilot control panel to the roll servo and not to the display. There isn't a lot of benefit to connecting the GMC 307 to the display. The connection to the roll servo is the important connection and the only one that matters if your GDU 460 becomes unavailable and you need to operate your autopilot using the G5 and the GMC 307.
One additional comment. We noticed you had a GMA 240 audio panel in your list. This is a great audio panel, but you might also consider the new GMA 245 if you have not yet purchased the GMA 240.
Thanks,
Steve
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Thanks Steve!
That does clear up things a lot. And yes I'm out of serial ports - dropping the connection from the GDU to the GMC 307 would help. Jonathan at Garmin (email) has been helping clear things up too.
He said I do need two ports from the GDU to the GTN 625, one for MXMAP data and one for Connext - so my total ports that could be connected to the GDU are:
GSU 25 - I will connect with the dedicated port on P4601
GTX 45R for traffic and weather info
GTN 625 MXMAP channel
GTN 625 Connext channel
GNC 255A control and display of vor/loc info - Nav 2
GEA 24 redundant path for engine data
GMC 307 - will probably skip this one if all functionality is good through the roll servo connection.
Thanks again for all the helpful information and tips.
Another couple of open questions to you experts....
I'm currently planning on bolting the GSU 25 to the GDU - though Garmin is not endorsing this - I had done a quickie survey here a couple of months ago and the few RV-8 guys that responded did not think it would be an issue.
Anyone have a bad experience with this on an 8? My thinking is that the narrow cockpit / panel seems like it should be pretty solid. I'm not sure where else to mount the GSU that would be more solid and not vibrating.
Also, The Garmin "certified" manuals for the GTN and the GNC go into detail about prepping the mating surfaces of the radio racks and the instrument panel.... cleaning and alodining, then checking the resistance between radio rack and panel with a milliohm meter. Overkill? or worth the extra mile?
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