MGL Discovery Lite problems


Although my 750 flies very well (I have 50+ hours on it), I continue to
           have problems with my MGL panel. I have talked to both Matt at MGL and Wayne
at composite designs (LSA power panel) multiple times without success
in solving the problem. The bottom line is that my MGL radio (V6) and
Discovery lite EFIS  work fine while my engine (Jabiru 3300) is off. Once I start the
engine, the AHRS part of the EFIS quickly freezes, and my radio stops
working. The intercom works, the numbers stay on the face, but I don't
receive or transit. Sometimes, keying the mike ( PTT button) will start it
working, but at best it's intermittent. If I recycle the EFIS power, the
EFIS will work for a while, then freezes again. Just the AHRS part. The
engine monitoring stuff from the RDAC has always worked fine. I traded out
the EFIS once to no avail. I put a capacitor across the power supply (as
suggested by both Matt and Wayne) to no avail. My first flight was 6 January 
            and other than my test area, I haven't ventured very far without a
           reliable radio and EFIS (I have steam gauge ASI, altimeter, skid ball and compass
as well as a garmin 496 so I've never been or felt unsafe). Even though I
            have about 8k in the MGL system (EFIS, radio, transponder and ADS-B), after 10
months, I'm about ready to throw in the towel and put in another system.
I've had an avionics guy working on it for several months now, redoing
grounds, checking coax and shielded wires, etc.  He is as befuddled as me.
           I can't help but think the Jabiru has something to do with this, and perhaps
specifically the voltage regulator (which I got a new one and changed as
well). My voltage regulator is wired as prescribed by Wayne for the Jab 3300. Anyone have any thoughts or ideas on this?  Thanks.

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Replies to This Discussion

Permalink Reply by Don Morrisey on November 8, 2018 at 7:08pm

Maybe its the engine but I think you have an electrical/grounding issue.  I would suggest signing onto matronics.com and signing up for the aeroelectrics email forum and post the issue there.  Some very knowledgeable folks there... here's a link:

http://forum.matronics.com/viewforum.php?f=3

Permalink Reply by Carl Orton on November 8, 2018 at 9:20pm

Do you have ALL grounds connected to a "forrest of tabs" panel?

Do you have any RF cable running right alongside a data cable?

Permalink Reply by Rodney Hall on November 11, 2018 at 10:13am

I tend to agree it is probably a grounding or connection issue. When the engine is off, no vibration, engine on. vibration causes your problem. This would seem to indicate a bad ground issue or loose connection. The only other thing may be some sort of interference from the alternator but you can test that theory by disconnecting it from the system and running the engine with the instruments running either off a ground source or just the battery and see if it still happens. Since it seems to be something with ADHRS I might check that wiring first and also check for a power line running next to or near the ADHRS or it's data line causing electromagnetic interference..

Permalink Reply by stephen hetz on November 11, 2018 at 5:14pm

I actually did that (ran the radio and EFIS) directly off of the battery and disconnected the voltage regulator (and hence the power coming from the engine) with the engine running with the same results My plan is to again go over every ground and connection to the EFIS and radio and look for anything loose or improperly wired.  Vibration seems to be the source.  Perhaps the tenth time will be the charm. Thanks. 

Permalink Reply by David J Tillema on March 11, 2019 at 4:18pm

Any luck yet? I'm considering MGL , but this concerns me.

Permalink Reply by stephen hetz on March 12, 2019 at 8:12pm

Still trying to figure it out.  Honestly, no one else with an MGL system has ever contacted me with a problem similar to mine.  Matt, at MGL, has been extremely helpful, unfortunately to no avail.  After I sent my Discovery Lite EFIS back to be checked, he sent it back and said it checked out.  After a couple months, he agreed to completely replace the unit.  Same problem.   I has to be something unique to my engine, electrical system setup, however for the life of me, I can't figure it out.  I've had an avionics guy intermittently working on it for the last several months. He's rewired grounds, the jacks, etc.  No joy.  So, I think this is somehow unique to my setup and I'm not sure it's an MGL problem.  For what it's worth.

Permalink Reply by Jim and Amelia Isaacs on March 14, 2019 at 4:45am

The wires from your magnetos to your ignition/start switch, and the AC power wires from your engine to the voltage regulator, are each individually separate(not twisted pairs), individually shielded, and the shields grounded at the nearest point to the wire ends?

Permalink Reply by stephen hetz on March 15, 2019 at 7:42pm

They aren't twisted pairs, but they aren't shielded either.  Should they be??

Permalink Reply by Jim and Amelia Isaacs on March 15, 2019 at 7:50pm

Stephen,

Yes they should be.  Shield those wires, begin with the AC power wires from the engine to the external rectifier/regulator, start the engine, see if it makes a difference with your MGL.  Then shield the ignition wires.  Make sure you ground the shield braid. Hang in there, even if this does not solve your problem, keep at it, you will solve it.  

Permalink Reply by Mickey R. Mathieson on March 16, 2019 at 3:18pm
Permalink Reply by Mickey R. Mathieson on March 16, 2019 at 3:59pm

 Over twisting of wires can be problematic. 

Permalink Reply by Mickey R. Mathieson on March 15, 2019 at 1:44pm

 You mentioned you put a capacitor across the power supply. Connect an oscilloscope(DSO) to the same point as capacitor - set tigger for falling edge and record the data points of the failure.  The problem may be caused by voltage going outside the operating parameters of the electronics therefore causing a lock up.  Too high or too low voltage will cause strange problems. 

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