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Help, exit the Garmin 155XL enter a GTR225...

Dan 57

Dan 57

Well Known Member
Avionics nerd around? Or anybody taken the same or similar route?

Guys, I?m kinda struggling with a ?simple? exchange of radios?
Old panel:
Garmin GTX328 XPDR
Garmin 155XL GPS/COM
Flightcom 403mc INTERCOM
Sennheiser ANR powered headsets

New panel:
Garmin GTX328 XPDR (still the old one)
Garmin 225A COM (using the built-in intercom)
Bose A20 headsets

So I keep the GTX328, install the 225A instead of the 155XL. And get rid of the Flightcom 403mc and the powered ANR headsets.
Frying my COM with multiple trials is not an option, so here?s the stack of cards:

OLD: Flightcom 403mc 25 pin D-sub connector (ref Install manual pages 6/7)
Pin #1 / Ground / Avionics ground point
Pin #2 / Mic Audio / Pilot mic
Pin #3 / Mic Audio / Copilot mic
Pin #4 / Mic Audio / Passenger mic
Pin #6 / Copilot / Copilot PTT Switch
Pin #7 / Pilot / Pilot PTT Switch
Pin #8 / Transmit key / Comm radio keyline
Pin #9 / ICS Audio / Pilot headphone
Pin #11 / ICS Audio / Passenger headphones
Pin #13 / Mic return / All mic jacks
Pin #14 / Mic Audio / Passenger mic
Pin #16 / Copilot Transmit Audio / Comm radio
Pin #17 / Pilot Transmit Audio / Comm radio
Pin #18 / Aux input / Music system
Pin #20 / Power in / 12-28 V, 1 amp breaker
Pin #21 / Receive Audio / NavCom/Audio Panel
Pin #23 / Intercom Mute / None
Pin #24 / Aux Mute / None
Pin #25 / Mute Activate / None


NEW: apart from the power pins which are clear, the GTR225 (ref install manual page D-12) offers following (only the ones of interest to me and open to doubt are listed):
#11 / COM MIC 1 KEY
# 5 / COM MIC 1 AUDIO IN HI
#20 / MIC AUDIO IN LO

#26 / COM MIC 2 KEY
#6 / COM MIC 2 AUDIO IN HI

#7 / 500 OHM COM AUDIO HI
#18 / 500 OHM COM AUDIO LO

Which pins to use in the Garmin GTR225 D-sub connector, which are the matching pins?
What to do with the unused pins (and wires) on the Flightcom 403mc D-sub connector?
Regarding pin #1 on the Flightcom, Avionics ground, could I ground it to the aircraft or is that a case of grounding to the case as for the rest of the shielding?
There?s also an ARINC 429 2 pin connection between the old Garmin 155XL GPS/COM and the GTX328 XPDR, ref pins 15 & 16 install manual 155XL page 23. What is it good for and can I discard it?

Thanks for any input and help :)
 
DeeCee 57 said:
Avionics nerd around? Or anybody taken the same or similar route?

Guys, I?m kinda struggling with a ?simple? exchange of radios?
Old panel:
Garmin GTX328 XPDR
Garmin 155XL GPS/COM
Flightcom 403mc INTERCOM
Sennheiser ANR powered headsets

New panel:
Garmin GTX328 XPDR (still the old one)
Garmin 225A COM (using the built-in intercom)
Bose A20 headsets

So I keep the GTX328, install the 225A instead of the 155XL. And get rid of the Flightcom 403mc and the powered ANR headsets.
Frying my COM with multiple trials is not an option, so here?s the stack of cards:

OLD: Flightcom 403mc 25 pin D-sub connector (ref Install manual pages 6/7)
Pin #1 / Ground / Avionics ground point
Pin #2 / Mic Audio / Pilot mic
Pin #3 / Mic Audio / Copilot mic
Pin #4 / Mic Audio / Passenger mic
Pin #6 / Copilot / Copilot PTT Switch
Pin #7 / Pilot / Pilot PTT Switch
Pin #8 / Transmit key / Comm radio keyline
Pin #9 / ICS Audio / Pilot headphone
Pin #11 / ICS Audio / Passenger headphones
Pin #13 / Mic return / All mic jacks
Pin #14 / Mic Audio / Passenger mic
Pin #16 / Copilot Transmit Audio / Comm radio
Pin #17 / Pilot Transmit Audio / Comm radio
Pin #18 / Aux input / Music system
Pin #20 / Power in / 12-28 V, 1 amp breaker
Pin #21 / Receive Audio / NavCom/Audio Panel
Pin #23 / Intercom Mute / None
Pin #24 / Aux Mute / None
Pin #25 / Mute Activate / None


NEW: apart from the power pins which are clear, the GTR225 (ref install manual page D-12) offers following (only the ones of interest to me and open to doubt are listed):
#11 / COM MIC 1 KEY
# 5 / COM MIC 1 AUDIO IN HI
#20 / MIC AUDIO IN LO

#26 / COM MIC 2 KEY
#6 / COM MIC 2 AUDIO IN HI

#7 / 500 OHM COM AUDIO HI
#18 / 500 OHM COM AUDIO LO

Which pins to use in the Garmin GTR225 D-sub connector, which are the matching pins?
What to do with the unused pins (and wires) on the Flightcom 403mc D-sub connector?
Regarding pin #1 on the Flightcom, Avionics ground, could I ground it to the aircraft or is that a case of grounding to the case as for the rest of the shielding?
There?s also an ARINC 429 2 pin connection between the old Garmin 155XL GPS/COM and the GTX328 XPDR, ref pins 15 & 16 install manual 155XL page 23. What is it good for and can I discard it?

Thanks for any input and help :)
Click to expand...

Hello DC,

One thing for sure. You will gain some valuable skills/understanding before this project is over!

Since the GTR 225A will be your new pilot/copilot intercom and you will be removing the 403mc, we recommend you follow the guidance on page D-12 of the Rev. H GTR 225 installation manual for wiring the pilot and copilot headset jacks and totally toss the existing wiring to the 403mc.

If there is one thing you have to get right, it is the single ended shielding and headset jack isolation required for the pilot/copilot intercom audio functions. Trying to re-use the existing wiring and patch into the existing 403mc DB-25 connector might not provide the excellent audio results you will want.

As shown on that single page drawing, there really isn't a lot of wiring between the GTR 225A and the 4 pilot/copilot audio and mic jacks, so best to get some new shielded wire and go for it.

One thing we would recommend is to not try to wire for the hand mic PTT since no one uses those anymore. The Pilot PTT button will be wired directly to ground and pin 11 (COM MIC 1 KEY). The copilot PTT button will be wired directly to ground and pin 26 (COM MIC 2 KEY). This really simplifies your pilot/copilot MIC wiring and allows you to use a single shielded pair to each of those MIC jacks.

The pilot/copilot audio jacks will also use the same shielded twisted pair wire (normally 22 AWG).

The 155XL A429 to the GTX 328 was probably providing GPS data to the GTX 328 (check existing configuration for that input). You can get by without that, which is a good thing if you are removing the 155XL.

Please contact us directly by email shown below if we can assist in any way.

Thanks,
Steve
 
Garmin 155XL GPS/COM

''Garmin 155XL GPS/COM''

Isn't the 155XL an IFR GPS only without the Com ????

If so, any idea how much you're looking for it if still in good working order??

Thanks

Bruno
 
Steve, thanks a million for that quick answer! Appreciate and will go this way.

Bruno, the unit is a GPS/COM and sorry, but I already gave it away. The COM change is mandated by our EU Regs 8.33 :mad:
 
Garmin 155XL GPS/COM

''Bruno, the unit is a GPS/COM and sorry, but I already gave it away. The COM change is mandated by our EU Regs 8.33 ''

No worries, thank you for the reply.

Cheers

Bruno
 
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