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GNC300XL to INS429-No Course Input

cgrossl

Well Known Member
Sorry this is not RV related, but I wasn't sure of anywhere else to post a question like this. I've never ran across a general avionics forum on the net.

Anyway, my airplane came with a GNC300XL in the panel. I know its old, but it works great. I also had an INS429 so I thought I'd install it, as well as the an AK950L annunciator panel to get myself a basic IFR panel. I have no intentions of IFR flight, just wanted to be able to work on the rating.

The INS429 manual:

http://downloads.valavionics.com/INS_429_INSTALL_MANUAL_04-15 rev3.pdf

It includes an interconnect diagram (pg17) that shows how to connect it to the 300XL. That is how I wired them together. I have verified that the wiring matches the diagram multiple times. I talked to Val Avionics and they recommended that I send the INS429 back to them to see if the unit was producing an OBS signal. They verified that it was and did a minor alignment and sent it back to me. They are thinking that there is something wrong with my 300XL. I admit this is possible, but I think it unlikely. The reason is, that it was redone by Garmin back in 2004. It then sat on a shelf, or in the instrument panel for years and years until it was finally put into service last summer. It works great and it seem unlikely, at least to me, that only the circuitry that receives the course input signal is bad, and nothing else. I could very well be wrong on this.

My question is, what could keep the GPS from receiving the course input from the INS429? Other than that minor issue, the CDI functionality seems to work fine. Are the three resolver lines shown in the diagram what transmits this data? It would be really nice if the problem was just a setting, but I have seen no settings concerning the OBS resolver. I think it most likely that my problem was caused by me and my installation. 1 possibility that I came up with concerns a note on the INS429 Interconnect diagram. Note 4 says, "Connecting resolver to garmin units only requires 1 line, leave the matching pair disconnected." I followed these directions, but I wonder if I should connect the matching pair. I have asked VAL this and they say there is no need.

Thoughts?

Anybody know where I can send the 300XL to get bench tested?
 
Thanks for the help, but I must have not been very clear in my original post. This issue that I'm having is that the OBS course selection data that originates in the INS429 is not reaching the GNC300XL. So, this data would be an output from the INS429, and an input to the 300XL.

The INS429 is a self contained Nav receiver and CDI. It will also function as a CDI and OBS resolver for the 300XL which is what I'm trying to do. The CDI function works fine, but the 300XL says, "No Input" for the OBS. I won't claim to understand how all this stuff works, but I think this data is transmitted from pins 28, 10, and 29 on the INS429 to J1, Pins 14, 35, and 37 on the 300XL. I have confirmed that these three resolver lines are hooked up correctly.
 
Typically a Garmin panel-mount navigator will have a config mode page that displays the current state of its various external inputs. I would first look there to see if the GNC thinks it is receiving valid resolver data.

The installation manual also describes an OBS calibration procedure, which may or may not be necessary.
 
Yes, I have tried the OBS calibration page in the configuration menu. It says: "No Input"

To my knowledge, there is no other place in the configuration menu that will give any indication as to whether or not the GPS is receiving OBS input.
 
Cameron,

Do you have the A429 Input disabled on the GNC 300XL?

According to the installation manual "Course information can come from an analog resolver or from an EFIS via the ARINC 429 bus.".

If the A429 Input is enabled and set to "Selected Course" or "Course/Heading", perhaps the GNC 300XL disables the analog resolver input for course data.

Steve
 
Per the manual, the I.n.s course data is sent out via the RS232-out port. You need to connect this port to a RS232-in port on the gps configured to:
Format NMEA
Baud rate 9600.
 
Steve,
I haven't looked at the ARINC429 options or how they are set, but I will take a look. That makes sense.

Bob,
I'll take a look at that...it's definitely something I hadn't considered, but that does not agree with what Val told me. Also, I don't think the 300XL will interpret OBS data through the RS232 in ports.
 
Took a look at the ARINC429 settings last night. They weren't even turned on. I did try various combinations of setting the input to "Selected Course", "Course,Heading", etc. No matter what was selected, I still got " No Input" at the OBS calibration page.

I'm going to verify my wiring one more time. If its good, I'm probably going to send the 300XL off to get bench tested, assuming that I can find somebody to work on it.

My only other thought is that the INS429 isn't really compatible with the 300XL, even though it's documentation says it is.

I also like the idea of using RS232, but I don't see how I could get the GPS to interpret that data and then also use it in the proper place. Seems like I'd need to use some sort of ARINC communication from the INS429 if I wanted to do it a different way, but the INS429 doesn't do that.
 
I talked to VAL yesterday. They gave me some more insight into how the link between the INS429 and the 300XL is supposed to work. One of the resolver lines is a reference output from the 300XL that basically tells the INS429 where to start from. The other two lines coming from the INS429 are outputs that back to the 300XL as to what the OBS value is set at in reference to the signal coming from the 300XL. I'm probably not explaining this correctly, but this is what I understood.

Anyway, Val Avionics thinks that my GPS is not providing the reference signal to the INS429.

Anybody know where I can get a 300XL bench tested, and then worked on if need be?
 
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