KX155 weak

[Let'sgoflying!]

One of them is connected to the GS/LOC head and works great.'
The other 155 drives a VOR/LOC head and is weak, has been intermittently for a while. Audio is fine, DME range is the same, just the lazy needle til I get <25nm.
Radio guy had two shots at it now I would like to:

Can I swap the plugs for the two heads as a means of troubleshooting..... or is the pinout way different?

Can I physically swap the 155's to troubleshoot it?

 

[Walt]

Dave,
If the indicators are KI 203, 204 I am pretty sure you can do that, however I would first unplug the one with the weak signal and clean both connectors and check for damage. Lots of problems are caused by the connector.
Walt

 

[Richard]

Dave,
If the indicators are KI 203, 204 I am pretty sure you can do that, however I would first unplug the one with the weak signal and clean both connectors and check for damage. Lots of problems are caused by the connector.
Walt

Yeah, do that but also check all the pins to see if they are not bent over by the last guy who jammed the unit into it's tray or for where the upholsterer shot the too long screw grazing the cable or where the last A&P bound the wiretie too tight causing a crimp in the cable.

Lance, what is the name of the diagnostic unit that can pinpoint the >ohms exactly along the length of the cable?

 

[Let'sgoflying!]

thanks W, they are a 204 and a 208.
I have had the connections inspected and cleaned already and will forge ahead with something else.. what about swapping the 155's?

 

[Walt]

Dave,
You can swap the 155s.
Walt

 

[gismo]

Lance, what is the name of the diagnostic unit that can pinpoint the >ohms exactly along the length of the cable?

I assume you're thinking of TDR (Time Domain Reflectometry) which is a fancy way of saying "bounce a signal off the other end and see how long it takes". The first thing I'd check is the antenna connection. Granted the fact that you get good audio from the nav side says that it's not getting something from the antenna, but I've seen cases where the rcv audio sounded OK but there wasn't enough noise free signal to nav well. AFaIK you can swap the two radios for a test although you will lose the GS by doing so. If the problem moves with the radio, you know where the trouble lies. If not the most likely failure beyond the antenna connection is the nav head which contains the circuitry that decodes the radial. Swapping connections to the nav heads should resolve that.

 

[Let'sgoflying!]

Switching kx155s did not change much. Nav head two was still flakey. Sometimes it was OK, then it crapped out completely.
Radio guy says send in the head, they often need new Gain Controls; not too expensive.