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I am trying to solve a year and a half problem(since I started the engine) keeping my radio from working. I have a MGL V6 radio in my Sonex (Jabiru 3300 Gen 3 two wire alternator).
I have the issue of the radio stops working after the engine is started. It locks up and will not receive or transmit. It works fine on the aircraft battery, engine off, or with a external battery (only connected to the radio) with the engine running. I have tried a different antennae( mounted to a sheet of aluminum out of the aircraft), My handheld radio connected to the aircraft antennae(worked fine), I added a capacitor at the aircraft radio power wires, I changed my regulator, I added shielding to the wires from the alternator to the regulator, I wired the aircraft ground wire directly to the battery, I changed the power wire to the radio to a different bus, I have added ferrite beads(2) wrapped 15 times on the power and ground wires of the radio, I have checked the plug wires and distributor caps for tightness, MGL has sent me a new radio to try (Matt has been great at trying to help!), and probably more things I have forgot. It seems to me to be "noise" coming through the power wire since the only way it works is with a external battery when the engine is running.

If anybody has had this problem and solved it, I would appreciate the help.
Thanks, Jeff

I believe MGL says the radio must be off when starting the engine. Do you mean when you turn it on with the engine running, it just doesn't work?

Correct, it is off for start. And fails shortly after engine start and transmitting.

You said it fails "after engine start and transmitting". Does this mean it fails when you push the PTT switch? If so, I'd check the PTT wiring vs. the schematic. Does it receive anything before that happens?

What does "lock up" mean? Does that mean the screen still displays stuff but doesn't respond to button presses or knob twists? Or does the screen just turn off like the power is off?

I assume you have an EFIS or something else on the bus and that's working fine?

Any chance you can connect an oscilloscope to the 12v input to see what's happening? If that's not possible, maybe a multimeter voltage measurements in DC and AC modes? See how the measurements change before and after you start the engine. In the case of significant ripple, I'd suspect lower DC voltage and an AC measurement of a volt or more after engine start. This would probably indicate a wiring problem around the alternator/voltage regulator.

It usually transmits and receives for a little bit(seconds to minutes) before it fails. No transmission or receiving when it fails, until it is turned off and back on. Everything on the radio(lights, digits, frequency changes, etc..) works. everything else on the bus works normally. The voltage (on the MGL IEFIS light) shows about 12.8-14.1 volts with the engine running. I don't have an oscilloscope unfortunately. I don't think its the PTT or other wiring since it works on the external battery and ships battery fine. I think the alternator/voltage regulator may be the issue, but how to find out what it is and how to fix it, is what I don't know how to do.

A friend had the same problem with an MGL radio on a CRI Cri (this was a radio with the 2 1/4" face0. Worked fine until one or both of the engines were started and then the radio would just lock up and the power had to be disconnected before the radio could be used again with no engines running. After hours wasted fault finding the radio was swapped over to a different radio, Microair I think. Problem solved.

Thanks Phil, I'm almost to that point.

I'd double check the regulator wiring. Make sure that the black wire on pin 2 has a good connection to the battery. If I remember correctly, I connected the pins 5 and 6 (yellow and red) to the positive terminal of a large capacitor withing a few inches from the regulator. You may want to try to connect them together right at the positive terminal of the battery.

I don't see a reason to have the yellow wire connected to the "main buss" with the short distances we're running, and I wanted to make sure I had good voltage regulation.

good luck

I could be wrong but, I think the yellow wire draws a small amount of current all the time. Therefore
it should be connected to the master buss so it can be totally disconnected and not kill your battery over
time.

Rick

Has anybody used the v6 radio with no issues like this in a Jabiru powered Sonex?
I did have the large B and C capacitor next to the regulator but it did not help. The yellow wire is the voltage sense wire connected to my bus. I have moved the location of it with no change.