XPDR Caution

[swatson999]

Yesterday, twice I got a XPDR Caution message (something like that, don't have the screenshot handy), and when I went into the menu, it said something like XPDR TX PSU (36) (I think it was 36...in any case...)

Cleared both times with a power cycle, didn't happen again in ~6 hours of flight since.

What is it? Should I be concerned?

 

[dynonsupport]

We'd really need to know the exact error message or number to help. It could be anything from an internal failure of the transponder to a loose power wire to a failing piece of coax. The exact error will help us narrow that down instantly.

 

[swatson999]

Ask and ye shall receive:

TX PSU LOW (39)

Also weird...got a single caution about a touchscreen error...cleared and went away and never came back (today).

 

[jakej]

Steve

A thought here - doublecheck that the TNC connector is screwed fully home & the pin is close to flush with the end of TNC - I found an 'issue' with mine while doing a Txpndr check, wasn't screwed in fully 

 

[swatson999]

I'll check that during annual...it's a PAIN to get back there to the XPDR location (behind the baggage bulkhead)...unless it comes up again. Interested in what Dynon says the code indicates.

Didn't get the message again during 8 hours or so of flight this weekend.

Thanks for the tip, jake...I'll keep it in mind. Did you get this caution message, or just an off-nominal XPDR check?

 

[jakej]

Steve
Just off nominal (lower power than required) during the check - it was just a thought anyway for your situation, didn't realise it's a hassle for you to get at.

 

[dynonsupport]

We do document all of the transponder warnings on Page 11-17 of the SkyView System Installation Guide, including this one:

TX PSU LOW – Power supply voltage is low

What did your voltmeter say about your system voltage?

Ask and ye shall receive:

TX PSU LOW (39)

Also weird...got a single caution about a touchscreen error...cleared and went away and never came back (today).

 

[Carl_Froehlich]

Assuming your battery is not flat, make sure your power lead breaker terminal connections are tight. I tracked down a similar COMM/NAV problem to a loose breaker connection.

Carl

 

[swatson999]

We do document all of the transponder warnings on Page 11-17 of the SkyView System Installation Guide, including this one:

TX PSU LOW – Power supply voltage is low

What did your voltmeter say about your system voltage?

Ask and ye shall receive:

TX PSU LOW (39)

Also weird...got a single caution about a touchscreen error...cleared and went away and never came back (today).

Cross-correlating the Alert log with the User log, I can see the voltage dropping down to around 9 during engine start (first start the battery was a tad low after having not flow for about a week and a half)...what I would say is normal engine start "sag", but I'll have to go look and see how it behaved before.

This was the case both times (initial start to taxi for fuel, start after fueling).  No further occurrences the rest of the weekend with a lot of flying.  So I'm guessing that was it, but a quick question...once the battery voltage goes back *up*, which it most certainly does after engine start, to nominal values, shouldn't this clear itself?  Recovery required a power cycle, which doesn't seem right to me...

For the record, here is what I see in the logs:

Alert log
12.19 ... 1/8/2016 19:29 34.25997 ... 19:29:48 TEXT SHOW alert
XPNDR WARNING MES


User log (key columns only)
Session Time GPS Fix Quality Number of Satellites GPS Date & Time Transponder Status Transponder Reply (bool) Transponder Identing (bool) Transponder Code (octal) Volts 1 Amps

11.56 1 10 1/8/2016 19:29 1 1 0 1200 11.7 -11.9
11.81 1 10 1/8/2016 19:29 1 1 0 1200 10.1 -11.7
12.06 1 10 1/8/2016 19:29 1 1 0 1200 9.4 [/b]-11.4
12.31 1 10 1/8/2016 19:29 1 1 0 1200 9.3 -11.3
12.56 1 10 1/8/2016 19:29 1 1 0 1200 9.4 -11.3
12.81 1 10 1/8/2016 19:29 1 1 0 1200 9.6 -11.7
13.06 1 10 1/8/2016 19:29 1 1 0 1200 9.8 -12
13.31 1 10 1/8/2016 19:29 1 1 0 1200 10 -11.9
13.56 1 10 1/8/2016 19:29 1 1 0 1200 10.4 -10.2
13.81 1 10 1/8/2016 19:29 1 1 0 1200 11.5 -5.7
14.06 1 10 1/8/2016 19:29 1 1 0 1200 12.6 -1.7

 

[swatson999]

Assuming your battery is not flat, make sure your power lead breaker terminal connections are tight.  I tracked down a similar COMM/NAV problem to a loose breaker connection.

Carl

I'll double-check those, too...they're Fast-Ons into a fuse block with ATC fuse blades, so unlikely to be lose, but might have acquired some oxidation and need cleaning. Thanks for the tip! (Good preventive maintenance to check all of them every so often, anyway...)

 

[Carl_Froehlich]

I'll double-check those, too...they're Fast-Ons into a fuse block with ATC fuse blades, so unlikely to be lose, but might have acquired some oxidation and need cleaning.  Thanks for the tip!  (Good preventive maintenance to check all of them every so often, anyway...)[/quote]

Don't assume a fuse is good - swap it out. One plane I worked on got a bad batch of fuses that had internal high resistance under load.

Carl

 

[swatson999]

I'll double-check those, too...they're Fast-Ons into a fuse block with ATC fuse blades, so unlikely to be lose, but might have acquired some oxidation and need cleaning.  Thanks for the tip!  (Good preventive maintenance to check all of them every so often, anyway...)

Don't assume a fuse is good - swap it out.  One plane I worked on got a bad batch of fuses that had internal high resistance under load.

Carl
[/quote]

Been working fine for 3 years...so I doubt the fuse has "gone bad".

 

[jakej]

Steve

Are you saying you have the Transponder powered up while cranking engine ?

 

[swatson999]

Yep. Always have.

 

[jakej]

DS may want to chime in here as this may be related.

I had a situation here where the Hex code was changing to a different one other than the correctly set code - turns out it only happened if the Txpdr & SV's were powered up together & had not fully booted up.  It was hard to troubleshoot the issue due to circumstances with aircraft being in another State.  However after discussions with Trig, our regulator & Dynon, & some own troubleshooting we found that changing the Transponder power to the avionics switch (in other words powering the Txpdr after SV has booted up) we've had absolutely no problems since.

Worth a try as it's easy to do ?  Regardless of the outcome of your situation it's something for others to be aware of to.

 

[swatson999]

No can do...no avionics switch.

 

[dynonsupport]

Jake,
The ICAO address vulnerability was addressed in a firmware update for the transponder a while ago. We haven't heard of any other issues with it being on during engine start.

 

[jakej]

DS, thanks. I wasn't aware the update specifically fixed that problem

Jake J

 

[swatson999]

Got the same error again today. Power cycle the main buss fixed it. Will get the logs tomorrow and look at them...

 

[swatson999]

Got a similar caution again today, did a screen capture of the message in the Transponder menu, and downloaded a diagnostic file.

This was during a hot start after fueling (after a short taxi from the hangar), and (unusually) it took a couple of times to get the engine going. My hot-start procedure must have been a little off today. Today is was "RX PSU FAIL".

Power cycling cured it...but why is it doing it in the first place? And it seems this message and/or subsystem off-line condition *persists* after power comes back up following the start?

I'll do the same thing as before, checking the logs...but perhaps Dynon could weight in with some info on their architecture and if that is expected (as perhaps a side-effect)?