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Dynon panel failures

BrandonN

I'm New Here
Hello all,

I have a friend with a new to him RV9A that we are having some problems with.

EFIS-D100, EMS-D120, Garmin GTR225, Garmin GTX345, and Dynon AP74.

Every once in a while the 2 dynon screens will just go black. The D100 has a battery back up and the battery back up does not activate or keep the unit running. The failures have happened more frequently lately and now correlate with the push to talk being activated (screen go black when PTT is pushed). Cannot duplicate the problem on the ground and still very intermittent. The screens are powered by separate circuit breaker style switches and obvious defects of grounding have been looked at.

One time the screens came right back up when cycling the switches, but on another occasion cycling the switches did nothing.

Any ideas? Thank you all.
 
Hello all,

I have a friend with a new to him RV9A that we are having some problems with.

EFIS-D100, EMS-D120, Garmin GTR225, Garmin GTX345, and Dynon AP74.

Every once in a while the 2 dynon screens will just go black. The D100 has a battery back up and the battery back up does not activate or keep the unit running. The failures have happened more frequently lately and now correlate with the push to talk being activated (screen go black when PTT is pushed). Cannot duplicate the problem on the ground and still very intermittent. The screens are powered by separate circuit breaker style switches and obvious defects of grounding have been looked at.

One time the screens came right back up when cycling the switches, but on another occasion cycling the switches did nothing.

Any ideas? Thank you all.

Try powering them up directly ie bypass the circuit breakers.:). FWIW - I never use circuit breaker switches.
 
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He called them. They didn't really have any ideas and had never heard of it.

There is a whole host of possible issues with the electrical connections, wiring, and others that have nothing to do with the specific Dynon equipment and it is difficult to diagnose with so many open questions.

Have you tried to contact someone who knows avionics and electrical system to look over your friend's airplane? It is a going to be a laborious process tracing one wire at a time if the electrical system schematics aren't professionally produced.
 
Sounds like some real weird wiring quarks in that plane. A whole electrical system review might be in order unfortunately.
 
Thanks for the replies.

It was on the list to try (if it will duplicate the failure) is to try turning on the D100 with the battery right after the failure and see if it will come on.

Hard part to swallow is that the system has 500 plus hours on it and just starting doing it out of nowhere.
 
Some things to check:
1. Does the battery keep the D100 alive for 30 seconds when you power down the avionics, there was an early SB to remove the power to the "keep alive" function that trickle charged the battery. If the battery does not keep the system alive it is probably shot (mine is still working fine after 14 years)
2. Do you get any DSAB errors on the D100 or D120?
3. How are the power wires connected to the busses, I have had a situation where the spade connector got hot and corroded which caused a voltage drop across the connector under load, took ages to find it as it read 12v with a meter.
4. My D120 will occasionally restart on a engine start on a cold day when the voltage dips. Is the radio pulling down the voltage somehow? (I am not an electrical engineer)
Just some thoughts
Figs
 
1. The battery does operate correctly when the unit is shut down and comes up with the 30 seconds of battery power. It does not function correctly when the problem occurs and the screen goes black. He is planning to try it if he gets another failure and see if he can manually turn the screen on with the battery after it goes black.
2. No DASB errors.
3. Power wires look good with no corrosion or obvious defects and good voltages. And keep in mind that both screens are going black, but they have completely separate power wires and grounds.
4. He tried letting the battery drain down to 11 volts or so in the hangar and using the PTT to see if he could get a failure in the hangar and everything worked perfect and could not duplicate failure.

Thanks again for the ideas.

He did talk to Dynon again yesterday and sounds like some of them had a pow wow together and think it could be internal in one of the screens and causing the other to fail also. Sounds like it could be expensive to repair the screens if needed:(.
 
He did talk to Dynon again yesterday and sounds like some of them had a pow wow together and think it could be internal in one of the screens and causing the other to fail also. Sounds like it could be expensive to repair the screens if needed:(.

This makes the most sense to me, given the symptoms you posted here.

Larry
 
if I remember from my last repair Dynon charges a flat rate ($400?) to fix their equipment
Figs
 
An update and more questions.

The dynon units were sent back to Dynon for evaluation and passed all tests with no problem found. Put units back in and same failure of both screens when pushing the PTT.

More information gathered since then:
1. The failure will only happen when it's cold, once things warm up the failure won't occur.
2. The units are not actually powering down, it's like the backlights are going out, you can still read the screens if in the correct light, just super faint.
3. The EMS-D120 has 2 plugs on the back. One for power/ground/connect the 2 screens and one for all the engine sensors. If he unplugs the harness for all the engine sensors the failure will not occur.

The next obvious step is to isolate each engine sensor one by one, but just seeing if anyone else has ever seen anything like this before?

Thanks!
 
How old is the Dynon equipment?

Some of the original EMS units had trouble with RFI (Radio Frequency Interference) coming in through the sensor wires from a radio transmission. From your troubleshooting, it sounds like that may be your problem. They have a RFI filter device that can be placed into the EMS but you'll need to send the EMS back to Dynon for that service. Get the serial number off the EMS and talk to Dynon about, I think it's likely that will fix you up.
 
#3 may be a pretty good clue. The "engine sensors" as you call them are all thermocouples. There are four CHT and four EGT thermocouples in there, and thats all. Strange things happen sometimes when thermocouple sensing ends (called junctions) are grounded. Maybe the PTT creates some current loop with a thermocouple that is troubling it. Try disconnecting all the CHTs at the cylinder heads (easy to do, they are sort of bayonet connections) and see if the problem goes away. Then try disconnecting all the EGTs at the engine (there are screw terminal splices in the wires about a foot from each EGT probe). If either of those tests make the problem go away, you have a bad thermocouple.


An update and more questions.

The dynon units were sent back to Dynon for evaluation and passed all tests with no problem found. Put units back in and same failure of both screens when pushing the PTT.

More information gathered since then:
1. The failure will only happen when it's cold, once things warm up the failure won't occur.
2. The units are not actually powering down, it's like the backlights are going out, you can still read the screens if in the correct light, just super faint.
3. The EMS-D120 has 2 plugs on the back. One for power/ground/connect the 2 screens and one for all the engine sensors. If he unplugs the harness for all the engine sensors the failure will not occur.

The next obvious step is to isolate each engine sensor one by one, but just seeing if anyone else has ever seen anything like this before?

Thanks!
 
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