URGENT REQUEST Transponder Test Failed

[Dynon101]

Can someone PLEASE help me troubleshoot a failed test transponder?

I tried to get a pitot static test today and the system failed the transponder Mode S interrogations received component of the test. He was using the Tol-Instruments T-48 MODE S/ATCRBS TRANSPONDER RAMP TEST SET. He said that the test set was receiving between 65 to 100 percent of the interrogations and the device reports the lowest number as the result and anything less than 90 percent is considered a fail so my system got a 65 percent.

After the fail I switched the antenna from the transponder to the ADS-B antenna and the result was the same so it seems that the antenna was not at fault.

The technician had me switch it to Mode A and he used a different test kit called a AV-17 AVIONICS TESTER and the mode A and Mode C system worked great with 100 percent replies received however when he uses the T-48 MODE S tester the same problem.

The transponder is the -261 unit.

The setup shows the following:

ON-LINE HW22.03 FW01.02 SW02.11
USA 91.227 COMPLIANT NO
GPS DATA (OFFLINE) GARMIN ADS-B/ADS-B+
PRESSURE ALTITUDE OK SKYVIEW
TAIL NUMBER shows my N-Number
TRANSPONDER HEX CODE A0088C
ADS-B IN FREQ (BOTH SV-ADSB-472)
TIS TRAFFIC is ON

What troubleshooting steps should I take now. He is coming back to the airport tomorrow so if it is something that I can reprogram of fix please let me know.

 

[swatson999]

This may not help, but my pitot/static/xpdr test guy 2 years ago had some issues with non-compliances that he knew were because of the test antenna positioning/proximity (he said he often has them with certain equipment), and he repositioned his equipment and such and it passed. I do *not* remember which part was failing, but he knew it was *not* the on-board equipment but rather the test set-up.

I know that's not much help, but it might give you an idea for a path to look into...

 

[Dynon101]

Dynon tech support called back and here is the report:

He walked me through the set up procedure and said that the transponder and ads-b both need to be connected and running so perhaps that was the trouble.

He also said that we do not have to fool around with the air/ ground mode disable of the transponder all we need to do is enter the static system test mode and conduct the test so perhaps that might have been the other problem.

The third possible problem is the Garmin was the unit sending the position data to the system and we change that to the Dynon antenna.

The fourth possible problem is the voltage should be about 12.4 Volt or more and it was 12.3 volts because the Garmin was running. Now that the Garmin position data is out of the loop I could have that off and use the zaps to power the bus north of 12.5 volts. I am using a small automotive battery charger and with all of the equipment running I see the voltage on the busses to be closer to 12.3 when I pull the CBs for the Garmin the volts jump up to 12.5

 

[Dynon101]

Hey everybody…you can uncross your fingers and toes!!!

The transponder passed!!!

The only thing that I did different was to program the Skyview to get its GPS data from the Skyview GPS as opposed to the GARMIN GTN-650 and I pulled the CBs for the Garmin so that way the automotive style 10 amp battery charger would keep the volts on the bus about 13.3 volts…with the Garmin up and running it draws a fair amount of zaps and the voltage on the bus was more like 12.3 volts and Dynon Tech Support said that 12.4 volts was the minimum they would like to see to have the transponder work properly…

Thanks again for your help!!!