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Trutrak ADI 2 Not Receiving GPS Signal

Pilotjim77

Well Known Member
My TT ADI Pilot II is functioning only in the gyro backup mode. My avionics shop recently installed a G430W and 2 older GRT Efis displays (WS). When they tested the panel, the autopilot was working correctly. However, now it does not seem to be receiving input from the GPS.

Before bringing the airplane back to the shop, I would like to do a voltage check on the autopilot input pins on the harness. I understand that pin 17 is the serial input, and pins 14 and 15 are the arinc inputs. What voltage should I expect from these pins when I power up the 430 and the GRT Efis displays?

Are there any other reasons I might not be getting input from the GPS?
 
If those pins are the signals from the gps to the autopilot I’m not sure measuring the voltage is going to help. Better to confirm in the configuration of the units that the protocol settings are correct and compatible between the two units. My guess is that somehow the config got changed on one or both units somehow.

I don’t know the boxes and don’t have the manuals but the details should be in the manuals.
 
If those pins are the signals from the gps to the autopilot I’m not sure measuring the voltage is going to help. Better to confirm in the configuration of the units that the protocol settings are correct and compatible between the two units. My guess is that somehow the config got changed on one or both units somehow.

I don’t know the boxes and don’t have the manuals but the details should be in the manuals.

I have checked the baud rate settings, and they are set at 9600.
 
Jim,

Since these are serial data paths, voltage wouldnt lead you to much unless you are able to look at the square wave coming out (which most multi-meters wont do).

One thing that I have done in the past to troubleshoot data paths if I am still getting issues after verifying configuration and continuity is correct is to listen to the bits coming out. This can be done by taking your headset and connecting a lead from serial output to either the left or right ear portion of the headset's jack. This can help you validate that data is actually flowing.

I encountered a time when my Arinc output from a unit was only active on the B channel. Continuity and configuration checked out okay, but the unit was not sending any 1s or 0s to the receiver on on of the two lines...

Note that the Arinc will be out from the Navigator on both wires while the RS-232 will be in on one and out on the other. So three of the connections can be verified with the AP control head off, while the AP output would be verified with the Navigator off.
 
Also, please check the output type in the 430W as well as which output (in addition to the baud rate).

You can email at the address in my signature and I will gladly help directly as well.
 
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