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PH-SCP

Well Known Member
Hi guys,

I am replacing my PS Engineering PM3000 with an Garmin GMA240 and adding a GNS430 to my SL30.

The idea is to work from the 25DB connecter that is already there (to connect the PM3000) and make a new harness from there to hook up the new GMA240 and GNS430.

The manual says to use 24gage shielded wire. I am a complete zero with avionics and try to learn as much as possible before attempting building a harness. I cannot imagine using a shielded wire for each connection and daisy chaining them all together. That would mean 35 shields tied together. What is the secret here ? What kind of cable should I use ?

Your hint are much appreciated !
 
PH-SCP said:
Hi guys,

I am replacing my PS Engineering PM3000 with an Garmin GMA240 and adding a GNS430 to my SL30.

The idea is to work from the 25DB connecter that is already there (to connect the PM3000) and make a new harness from there to hook up the new GMA240 and GNS430.

The manual says to use 24 gage wire. I am a complete zero with avionics and try to learn as much as possible before attempting building a harness. I cannot imagine using a shielded wire for each connection and daisy chaining them all together. That would mean 35 shields tied together. What is the secret here ? What kind of cable should I use ?

Your hint are much appreciated !
Click to expand...

Hello Simon,

First, the GMA 240 installation manual recommends the use of 24 gauge or larger wire, and we always recommend 22 gauge as it is easy to work with and makes for a little more robust installation than 24 gauge.

Shielded wire is recommended in most cases, but it is seldom single conductor, so while there are quite a few wires needed to complete the installation, most are in 2 and 3 conductor shielded cables, so there are far fewer shields to land than the number of total wires. If you review the interconnect drawings at the back of the GMA 240 installation manual, you will see what we mean.

While starting with the existing DB25 connector for the existing intercom is one approach, having a really quiet audio panel installation that is a joy to use is dependent on having really good shielded wiring, and trying to pass headset audio and other wires through a connector on the way to the audio panel is not recommended.

We applaud your plans to "tool up" with a stripper, crimper, and materials to do this job yourself, but you might also consider one of the Garmin dealers who sell the GMA 240 as several of them also make harnesses. The GMA 240, GNS 430, and SL 30 are very common components and if you asked someone to make you a harness with headset/mic jacks and some PTT wiring, we suspect you would be surprised how affordable it is to order this harness.

Stein Air has some really great videos to learn the basics of wiring if you want to start there.

Let us know if you have additional questions.

Thanks,
Steve
 
Thanks Steve,

I appreciate your long answer. What would a novice do without this forum ??
Very helpful indeed. I am going to be hardheaded and build a harness based on the DB25 connector. It is going to be a nice lesson.
If this brings about too much noise it's rewiring time and I'll start from scratch.

Thanks again for your help :) :)
 
For shields, generally it is acceptable to use 'pigtails', eg, solder a short length of #22 to the braid, cover with shrink tubing, then connect the wire to ground.

The caution from Garmin is that they know from experience how easy it is to put the wrong pin in the wrong hole, short adjacent wires, etc. It is possible to destroy your audio panel if the connector is mis- wired. That said, most people can do this. Just triple check everything before turning on the power.
 
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