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GRT TT22 Problem, Not Responding

C

CharlieL

Active Member
Hi all,
Thought I would describe an intermittent issue I've been having, see if any one else has experienced it or has ideas of what I could check next. I have dual GRT HXr EFIS with Trig TY91 comm and TT22 transponder. I will get a messages on the screen, usually "TT22 Not Responding". Sometimes "Trig Transponder Warning", or "Trig XPDR TX Restart". Sometimes it will IDENT all by itself, I'm sure ATC loves me when that happens! I've checked and rechecked wiring, actually rewired it using a new connector. I've changed antenna cable, checked ground connections, tried a different transponder, a different GRT controller. Also tried wiring it to the other EFIS. Sometimes it will act up while still on the ground, other times I might fly 45 minutes or so before it will act up. I've tried ferrite filters on various wires. About the only thing I haven't tried yet is a different antenna. I keep wondering if I'm missing something basic, but I can't think of anything. Any one experience anything similar to this? Thanks.
 
I'm dealing with some transponder issues right now. Ring out the antenna cable and antenna connection for continuity and no shorts.
 
On my first try I had a bad crimp/assembly of the TNC coax connector, so it didn't work at all. Re-did it, now it works fine. I'd say the odds are 99:1 that you've got an intermittent connection somewhere.
 
I've been troubleshooting a similar issue recently. I'm finishing up an installation on a client's Long-EZ which has an HXr and Mini-X. The TT-22 was originially wired into the two discrete RS-485 RX/TX pins on the mini, with the display-unit-link wired between the two displays via available RS-232 ports. I kept getting the same TT-22 Not responding messages on the Mini display, although I was able to see the squawk code field, and manipulate the transponder controls from both displays. I tried another TT-22 unit, no luck. I finally wired the TT-22 directly to a serial port on the HXr using the adapter module and it works fine.

Backtracking further, if I go into the General set-up menu on the mini and activate the TT-22 ports, it goes dumb, doesn't display synthetic vision, and repeats the TT-22 Not Responding message. My guess is an interface/software issue that needs to be investigated and worked out by GRT.
 
I have the same setup with no issues. Based upon the symptoms, I would be looking at a bad interface module. The F-F DB-25 that GRT gives you actually converts the the interface between the GRT and the Trig formats. It contains a processor and runs software. Assuming that the transponder is doing what it is supposed to and all of the errors are related to communication between the Trig and the GRT, this is where I would start. This diagnosis would seem to be confirmed by the fact that replacement DU's and Transponders show the same behavior.

You can re-download the s/w to this device or ask GRT to send you another one to help troubleshoot.

Larry
 
Thanks Larry, I've downloaded the software (several times) and, GRT has sent me another interface/controller to try. Still same problem. This one is a real challenge!
 
CharlieL said:
Thanks Larry, I've downloaded the software (several times) and, GRT has sent me another interface/controller to try. Still same problem. This one is a real challenge!
Click to expand...

I would consider examining the two RS-232 wires from end to end and possibly replace them just to be sure. It certainly sounds like the issues is in the communication link between the two devices, given that you have replaced both the DU and transponder with no improvement.

As a sanity check, you didn't wire anything to the RS-442 port, did you? I believe that will create problems as well for communication.

Larry
 
I've replaced all the wiring, including the connector at the transponder end. I also used shielded wire for the two control wires and for the power lead. I've recorded and sent a demo to GRT. There's noise getting in somewhere, just can't find it.
 
Take a good look at your ground connections. The instructions suggest using a minimum of two, I think, ground pins.
Something else: Look closely (or use an ohmmeter) at the 'power on' pin (I think it's pin 13) on the adaptor module. It should be grounded via a connection to pin 12 or 14 in the adaptor module. If it's a bad connection the transponder will go on and off. You might even just try running a ground wire directly to pin 13.
 
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Bob, I noticed that it's recommended to use at least two grounds. I've run a ground wire to all six pins labeled ground. Thanks for the tip regarding the "power on" pin. I'll give it a try.
 
Charlie, have you taken a good look at all the connector pins? Bent one...

And have you tried switching to anougther open serial connection? Number 8 perhaps? ( B7-white/green
B6-green)

Best regards,
 
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Thanks again for all the ideas. Last Friday I spent some time checking the antenna, rechecked the cable, rechecked all wiring. Took out the loaner TT22 and reinstalled my original, reinstalled the original GRT controller/adapter and downloaded the adapter software (again). I also wrapped the TT22 in tin foil (don't laugh!) and grounded the foil. Saturday I flew from Connecticut to Florida, Sunday to Sun n Fun, Tuesday back to CT. The transponder worked fine. At some point I will spend some more time determining exactly what the issue was. Right now I'm just glad it's working. My guess is that I will have to relocate the transponder, seems to be getting interference from somewhere. Who knew a little high tech Reynolds Wrap would be an essential addition to our avionics took kits?! Thanks again!
 
Trig 22 Issue

CharlieL said:
Hi all,
Thought I would describe an intermittent issue I've been having, see if any one else has experienced it or has ideas of what I could check next. I have dual GRT HXr EFIS with Trig TY91 comm and TT22 transponder. I will get a messages on the screen, usually "TT22 Not Responding". Sometimes "Trig Transponder Warning", or "Trig XPDR TX Restart". Sometimes it will IDENT all by itself, I'm sure ATC loves me when that happens! I've checked and rechecked wiring, actually rewired it using a new connector. I've changed antenna cable, checked ground connections, tried a different transponder, a different GRT controller. Also tried wiring it to the other EFIS. Sometimes it will act up while still on the ground, other times I might fly 45 minutes or so before it will act up. I've tried ferrite filters on various wires. About the only thing I haven't tried yet is a different antenna. I keep wondering if I'm missing something basic, but I can't think of anything. Any one experience anything similar to this? Thanks.
Click to expand...

If you have an older model Trig 22 Transponder you may need to send the unit to Mid Continent Instruments for a software upgrade. I had this problem and is now ok. Upgrade was free.
https://www.mcico.com/
 
Well done Charlie! Glad your making progress.

It seems to me that there are more high frequency (1090 MHz) transponder interference issues becoming evident. Headphone noise ticks with the squitter output. Data communication problems.

Jesse brought up an interesting point...could a poor coax connection, ,output or ground, a poor ground plane connection, or even as the OP stated an antenna problem cause an unbalanced transponder output, producing harmonic back feed aggravating or causing the problem? Just thinking out loud. Have you ever had a SWR check? Check with a dummy load? Just curious...
 
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The transponder is already completely enclosed in a metal box! RF can be strange, but I would again look at how or if that box is grounded, and make sure the coax braid is well connected at the connector, etc.
 
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