Transient Short Indicator -- Dynon, EarthX, VP-X

[rv7charlie]

Plus component tolerance drift in the vpx and/or the transponder. None of us have any way of knowing how close to the edge the vpx was operating for those years.

[spatsch]

Originally Posted by rv7charlie

Plus component tolerance drift in the vpx and/or the transponder. None of us have any way of knowing how close to the edge the vpx was operating for those years.

OK you convinced me. So I figured I will perform the following tasks in that order when I head back out to the airport:

1. Reproduce the fault and fault behavior -- make sure I didn't overlook something I should have noticed or noticed something that was a coincidence leading me in the wrong direction.
2. Check the Alternator wires and belt tension and general condition. -- easy to do and most people which responded public or private were voting for the alternator.
2. Increase fuse limit from 3 to 5 A on the VP-X. This would be the easiest fix as nothing is really broken... . Components just drifted a bit which is normal.
3. Replace the EarthX with my old battery. I got some private communication that indicates that the EarthX protective circuit could cause issues and it's easy to do as I still have the old battery takes 5min to switch.
4. Replace alternator -- I don't have a spare one so unless I find one I have to spend some $$. That's why I ranked it last even though most people are rooting for that one ... .

Thx

Oliver

[rv7charlie]

If your efis has data logging, look at the system voltage track over the period you've been having the overcurrent notices. If the alternator is going out of spec, you should see it in the history, even if the alarm set points are wide enough to hide it in real time.

If it were my system and everything is *functioning* correctly (voltage within limits, xponder works properly), I'd be betting on instrumentation error over any actual defects in the system.

Do you get to set the 'trip point' in that vpx circuit yourself? If so, how about bumping it up to 5 amps & see if you still get the alert.

[spatsch]

Originally Posted by rv7charlie

If your efis has data logging, look at the system voltage track over the period you've been having the overcurrent notices. If the alternator is going out of spec, you should see it in the history, even if the alarm set points are wide enough to hide it in real time.

If it were my system and everything is *functioning* correctly (voltage within limits, xponder works properly), I'd be betting on instrumentation error over any actual defects in the system.

Do you get to set the 'trip point' in that vpx circuit yourself? If so, how about bumping it up to 5 amps & see if you still get the alert.

OK I owe you a beer or something.

Went to the airport after work. I could reproduce the issue now reliably:

1. Switch alternator off to let battery drain a bit.
2. Switch alternator on -- transponder triggers as short
3. Wait till alternator load < 10A reset transponder everything works

Then I followed you advice and bumped the fuse value to 5A. Tried to trigger the short again on the ground and couldn't. Went flying and tried different things to trigger it and couldn't.

So that does seem to have solved the issue. Still baffled by the fact that it worked flawless for 4 years at a 3A setting... . What's the odds..... .

Oliver

[rv7charlie]

Glad you could solve it without injecting money. :-)

If you have data history from the efis, I'd still check the system voltage history. If the regulator's set point is drifting upward slightly, that could account for the change in behavior. Again, if the vpx trip point was very close to actual current over the prior years, even a very slight uptick in system voltage (even if well within normal range) could drive current up slightly, causing the current detection to fire.

[622BH]

This thread was very timely! After four years of flying (250+ hours) my SV-XPNDR-261 began tripping the VP-X Pro circuit when transitioning from GND to ALT mode.
Resetting the circuit resulted in the transponder operating properly throughout the rest of the flight. Until yesterday (Wednesday, 28 August) the circuit tripped twice. On the second tripping, I notices the transponder was pulling 4+ Amps during the transition from GND to ALT Mode. After resetting, it would only pull 2.5 Amps throughout the flight.
I sent an inquiry to Dynon late last evening before reading this thread. During the flight I thought that maybe "upping" the trip-point on the VP-X Pro might be in the plans, but I'd wait until I heard from Dynon.

Seems odd - interesting - transponders from the same manufacturer with VP-X Pro in different aircraft, each with about four years of operation are experiencing very similar issues...

And like the OP, - S.A. comments about swapping out the VP-X Pro to archaic circuit breakers is not in the works - no panel space and not going backwards in technology.

[Carl Froehlich]

Perhaps a simple test. Bypass the VPX and power the transponder (or anything else you suspect) via an inline fuse. It all works then you verified the VPX is the issue.

Carl

[sailvi767]

When did you switch to the EarthX battery? They typically initially charge at a higher amp rate verses a standard battery. Asking because you mentioned the charging amps in your solution.
G

[rapid_ascent]

This could all make sense if it was just a marginal condition that is resulting in the transient condition. If the transponder has a switching power supply then at a constant power out and a lower voltage in it will draw more current. That means it could be just marginally triggering the fault condition in these events. Your ground test seems to align with this argument. Bad or deteriorating connections could cause the same result though so that would be worth checking as well.

[Mich48041]

The reason a problem is showing up after 4 years is because it took that long for
corrosion to form on a bad connection. Take all connections apart, both power and ground,
and clean and reassemble. Tug firmly on terminal wires to be sure that crimps are secure.