Need help troubleshooting CDI glideslope

[Seth1001]

Hey fellas,

I got a KI-209 hooked up to a kn-57 (i think) glideslope and a kx-170. A while back the thing started being intermittent and then just took a total dump. I changed the navcomm, that didn't work. I changed the 209, same result. What else could it be? The antenna maybe? Clearly the thing gets power because it twitches when I turn on the navcomm. But I can't get any reading from it when I use the test VOR frequency. When I'm flying I'll see the glidescope line move like that's working, but the CDI needle is dead, no to or from indicator, just flags. What else could be my problem? Any suggestions? Thanks.

[Rick Junkin]

I had something similar and it was a wiring problem. I believe it was at the connector, bad crimp or recessed pin that lost contact. A check of the connectors for pin and crimp integrity is a starting point, followed by ringing the course indicator wire for continuity.

Cheers,
Rick

[PeteMc]

I'm with @JunkmanDifferent issue with a radio, but the first thing the avionics guy did was check the connectors for a pin that had pushed back (even just a little).  We did move on from there and found a different configuration issue, but going back to test all the pins was still on the list if needed.  You could easily have a bad crimp or even a broken wire even if the pins look okay

.

[PT20J]

My similar problem was also caused by a connector pin.

[Seth1001]

Alright I checked all the pins and that isn't the issue. I stared at the wiring diagram for a while and apparently pin 3 on the nav/comm is LOC out and pin 2 is the input for that wire on the KI 209. I'm gonna have to go back and figure out if I've got good continuity there. If continuity is good than the antenna must be the issue from what I can tell. Does any have any other theories?

[Seth1001]

Alright I've done a lot more troubleshooting and come to a conclusion, though I'd like some input from people if anyone knows anything. I've confirmed that there's good continuity on all the pins on both sides. I've confirmed that the indicator and the nav/comm are in perfect working order. I've confirmed that there's good continuity between the nav coax connector on the tray and the nearest coupler for that cable. My conclusion therefore is that there must be a problem with the antenna cable somewhere between that coupler and the antenna. It's worth noting that the nav/comm apparently gets no signal from the VOR antenna because there's no identifier or voice coming over the test frequency, unlike on navcomm 2, which gives me good morse. Both navcomms use the same VOR antenna if my understanding is correct. I'm pretty sure there's only that one on the tail. However, the center pin on the nav antenna tray connector has good continuity with ground, which is perplexing to me because that seems to indicate that the connection makes it all the way to the antenna. I've read lots of people arguing in various forums over whether or not that should be the case. I wanted to test nav/comm 2's connector see if it also grounded out but I couldn't get the damn thing out of the tray. I guess I could have disconnected a coupler and checked but I had other things to do. Does anyone have any inputs for me? 

[Aerodon]

On 5/7/2022 at 9:42 PM, Seth1001 said:

Alright I checked all the pins and that isn't the issue. I stared at the wiring diagram for a while and apparently pin 3 on the nav/comm is LOC out and pin 2 is the input for that wire on the KI 209. I'm gonna have to go back and figure out if I've got good continuity there. If continuity is good than the antenna must be the issue from what I can tell. Does any have any other theories?

You say you have a KN-57 - as far as I remember the KX170 series had this as a remote box for the ILS, and I don't see if you have tried or checked this out?

You 

 

 

Aerodon