MGL Avionics User Forum

Hi All,

Some times things just happen and I think not another issue with my Pilot side EFIS.

I can't believe the number of cracks and dry joints in this particular serial number EFIS has had, ( hang on, I better clarify something here, my plane has done just on a 1000's hours and the EFIS would be about 10 years of age, please read on), but the EFIS sitting right next to it in the same plane having done the same number of hours with the very next serial number, shows no signs of this type of cracking in the same places.

Yep, pulling electronics in and out of something does put stress on its components and wiring and this can cause issues and maybe this has helped cause this problem.

The other day, I turned the Pilot EFIS on and saw no readings for any of the sensors that are wired to the RDAC, but then after turning on the passenger EFIS which share the same RDAC, all the Pilot EFIS RDAC sensors came to life.

The first pic is of the 3 pins on the inside of the EFIS's rear panel that come through from the RDAC screw block, 2 pins supply the power to the RDAC and the middle pin is the signal from the RDAC. You may see the problem straight away and I think the bottom pin has the same thing happening.

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This pic tells the story once you move the RDAC screw block a bit, so a quick solder of all 3 pins should make them good for quite a few years.

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My guess is "work hardening" - the connector is vibrating and this ends at the solder joint. Eventually the point of highest flex on the solder hardens and eventually cracks. Yes a reflow of the solder (with a touch of flux) renews the joint. Try supporting the connector or wires to the connector to prevent another occurance.

Thanks Rainer,

I did not realize that solder get so brittle from vibration, but it certainly seems crystalized from this microscope picture.

My wires running to the EFIS were not that well supported when I removed my instrument panel for the first time, but they are much better supported now.

So I guess the take away lesson from this, take the time to make sure your avionics cables are supported as much as you can.

I think this pin finally cracked out after I tightened the RADC cables back into the connector this last time.

Cheers
JimJab.

Yep, vibration is a killer, specially on unsupported cables.
I have also had 2 instances where the SMA antenna connector on a V16 has undone itself due to vibration.
I am wary of overtightening them in case it puts excessive strain on the pcb solder joints, so now use sealant to prevent the plug nut from unwinding.
The V6 BNC connector was much more resistant with its positive bayonet locking, but the SMA makes sense from a manufacturing point of view.