Molex connectors and shielded wire

[alpinelakespilot2000]

I'd like to put a connector between my intercom and the headset jacks to facilitate panel removal. The harness Steinair provided for me uses shielded wire for the headset wires. If I cut the wire, can a Molex connector be used if I crimp the braided shielding to both the male and female connector just like I would do for the headphone and microphone wires? Would this defeat the shielding qualities of the wire?

Thanks.

[Canadian_JOY]

Steve - what you're suggesting to do is what is done at every disconnect point in an airplane, so your concept is good.

With that having been said, I'll also suggest your execution, as described, likely won't produce professional-looking results, and in the long run I suspect you'll be unhappy with the approach you've suggested.

If you look at the harness supplied by Stein you'll notice his folks use some fancy light blue terminations for the shield. These are made by Raychem and can be purchased from Aircraft Spruce or several other suppliers. While pricey they are THE way to terminate shields. Inside the light blue shrink tubing are three things.
1) a band of solder to completely encapsulate the shield strands and to make a positive connection between the shield and the short pigtail wire which you'll insert before shrinking.
2) a band of thick gooey adhesive that's used to seal the "open" end of the termination where your twisted wires exit
3) a band of not-so-thick gooey adhesive that's used to seal the opposite end of the termination, where the outer jacket of the shielded cable is still in place.

To properly terminate the shielded cable, remove about 1.5" of the outer tefzel jacket material. Carefully cut the braided shielding strands so that only about 1/4" projects from beneath the outer tefzel jacket. Cut a 22ga jumper wire approximately 2-3" long, strip one end about 1/4". Lay the jumper wire on the shielded cable such that its stripped portion is in contact with the 1/4" of bare shielding strands and its unstripped portion lies in contact with the outer tefzel jacket of the shielded cable. Now slide a Raychem termination onto the cable such that its solder band is positioned over the stripped end of the jumper wire and the bare shielding strands. Shrink in place, ensuring you've used enough heat to cause the solder band in the Raychem termination to melt. Now all you have to do is strip your jumper wire and the twisted wires from the shielded cable to the appropriate length, crimp on your Molex pins and insert them into the connector housing. Voila! A neat, professional shield termination that will stand the test of time and will allow you to easily extract connector pins if the need should arise.

Just for reference, these solder sleeve terminations are sold under p/n 11-04480, -04481 and -04482 by Aircraft Spruce.

As another note... Keep the unshielded portion of the wire as short as you can, consistant with being able to use connector insertion/extraction tools. And keep your pigtail wires short too so they won't act as antennas.

[az_gila]

Originally Posted by Canadian_JOY

......

As another note... Keep the unshielded portion of the wire as short as you can, consistant with being able to use connector insertion/extraction tools. And keep your pigtail wires short too so they won't act as antennas.

..use a maximum length of 1.5 inches for the unshielded pigtails at our VHF frequencies. Shorter is better though.

If you are going through a connector, then the sum of the pigtails on both sides should be less than 1.5 inches.

There are other good ways of terminating the shields into pigtails, but they require more work (but less $$$)

I bet Stein uses the ones mentioned above since they give him a more cost effective product at his hourly shop rate.
If your shop rate is less than Steins...... then some good shrink tube methods exist.

My home office is in the midst of a re-model, so I don't have any of my documents handy.... I'll look on-line...

ADDED

As always, AeroElectric Bob has a good reference....

http://www.aeroelectric.com/articles...l/pigtail.html

[SteinAir]

As most know, I am NOT a fan of connectors in audio lines. If your jacks are in the panel, and you want a quick way to remove the panel, it takes about 30 seconds to just unscrew the jacks and let them hang....then you have no break in the shield, etc....

If you are going to terminate shielding, do as others have said, but even better and fast is to use solder splices-which you'll notice professional shops use extensively when wiring up avionics (the G900 uses MANY, MANY of them, because almost every single connection on it is shielded and terminated at both ends),

Anyway, I can't see a compelling reason to do it, when the time/cost to do it far outweighs the time it takes to just remove the jacks.... This is one of those areas where I question the ends justifying the means. Of course I'm of the same opinion on lots of things when it comes to connectors. Having lived a previous life working on heavy iron, I'm firmly in the less connectors in the plane is better. They are natural homes that gremlins tend to live in. Not saying it can't be done, just saying we're going to have a difficult time troubleshooting any future audio issues when the harness is modified like that.

My 2 cents as usual!

Cheers,
Stein