Glideslope KX-165 + HSI KI-525A

[PeterRus]

Nav flag won't go away, and glide slope won't appear. CDI is working.

1. Noticed issues with NAV flag -- won't go away in NAV mode (GPS KLN89B works fine). Glideslope was unreliable, may or may not work

2. Took out the KX-165 and cleaned contacts, reinstalled -- first flight NAV flag was still there, but the glideslope/CDI worked. OK then...

3. Second flight back to normal: NAV flag is there, glide slope is not working

I understand the problems may be:

1. KX-165 glide slope circuitry needs attention

2. Wiring KX-165 -> HSI (or even antennae -> KX-165?)

3. HSI itself 

(or combination) The working (kind of) flight after contacts cleaning leads me to #2, however, #1 is also a suspect. Someone (avionics guy, either MidCont or Bevan? on the phone) mentioned HSI is an unlikely problem.

What are my options here?

1. Take the airplane to avionics shop to diagnose the issue (most logical step...)

2. Send the KX-165 for evaluation/repairs (and possibly the HSI)

3. Apply more elbow grease and then retreat to option #1 or #2

Edited August 25 by PeterRus

[MikeOH]

I can't offer any advice based on personal experience with your issue, unfortunately.  Only as an EE can I offer a few suggestions which may be of limited value based only on how I would approach this.

1) Avionics shop would not be my first choice.  Likely the most expensive path and still may not result in success if the wrong shop is chosen!

2) I would get ahold of @Jake@BevanAviation and possibly Bob Weber https://webairconsulting.com/  (Looks like you may have done this?)

3) A very large percentage of intermittent systems that had been previously working fail due to bad connections in my experience. So your 'more elbow grease' is a good one.  I would focus on all connectors, including those to antennae (GS in particular).  Not easy, but tracing the path of wiring looking for abrasion causing shorts.

4) Send the KX-165 out to be checked/aligned

5) HSI (internal issue) would be the least likely, IMHO.  But check the connector(s) to it!

 

Good luck!  Troubleshooting intermittent electrical problems is the worst!

[Shadrach]

5 hours ago, PeterRus said:

Nav flag won't go away, and glide slope won't appear. CDI is working.

1. Noticed issues with NAV flag -- won't go away in NAV mode (GPS KLN89B works fine). Glideslope was unreliable, may or may not work

2. Took out the KX-165 and cleaned contacts, reinstalled -- first flight NAV flag was still there, but the glideslope/CDI worked. OK then...

3. Second flight back to normal: NAV flag is there, glide slope is not working

I understand the problems may be:

1. KX-165 glide slope circuitry needs attention

2. Wiring KX-165 -> HSI (or even antennae -> KX-165?)

3. HSI itself 

(or combination) The working (kind of) flight after contacts cleaning leads me to #2, however, #1 is also a suspect. Someone (avionics guy, either MidCont or Bevan? on the phone) mentioned HSI is an unlikely problem.

What are my options here?

1. Take the airplane to avionics shop to diagnose the issue (most logical step...)

2. Send the KX-165 for evaluation/repairs (and possibly the HSI)

3. Apply more elbow grease and then retreat to option #1 or #2

I know it sounds ridiculous but I would remove the 165 and gently clean the connector strip with a pencil erasure on both sides, then wipe with an alcohol soaked Qtip (leave no fiber behind). With the box out, shine a light into the tray and get a visual on the female side of the connector. Ensure all the contacts are properly oriented and undamaged. Re-rack and test. If that fails, it will need to be bench tested. The good news is that it’s a very robust radio, and most of the parts are available save for the display which is unobtainium…

BE VERY, VERY MINDFUL OF THE DISPLAY WHEN HANDLING AND RACKING.

[Jake@BevanAviation]

What HSI do you have?  The KI-525A has a known issue of the G/S needle getting stuck from time to time.  I would give Mike or Tom a call to discuss the KX-165, there are some units that have capacitor leakage issues that can cause weird failures and be isolated to specific circuitry.

[PeterRus]

Thanks everyone. 

I have cleaned the contacts with isopropyl (no pencil eraser though) but didn't look into the trays -- will do that next. I hoped an avionics shop can help diagnose the connector issues before I send the radio. I have looked at the electrolytics, and didn't see any leakage or bulging.

@Jake@BevanAviation -- yes, the KI-525A -- not sure if NAV flag on and stuck glideslope are related?

[Jake@BevanAviation]

@PeterRus I believe the Nav and G/S are different meters.  I have not seed that many issues with the Nav flag function but G/S is a different story.

[OR75]

any option to borrow a 165 (or 155) to test ?

[LANCECASPER]

On 8/23/2024 at 2:36 PM, PeterRus said:

Nav flag won't go away, and glide slope won't appear. CDI is working.

1. Noticed issues with NAV flag -- won't go away in NAV mode (GPS KLN89B works fine). Glideslope was unreliable, may or may not work

2. Took out the KX-165 and cleaned contacts, reinstalled -- first flight NAV flag was still there, but the glideslope/CDI worked. OK then...

3. Second flight back to normal: NAV flag is there, glide slope is not working

I understand the problems may be:

1. KX-165 glide slope circuitry needs attention

2. Wiring KX-165 -> HSI (or even antennae -> KX-165?)

3. HSI itself 

(or combination) The working (kind of) flight after contacts cleaning leads me to #2, however, #1 is also a suspect. Someone (avionics guy, either MidCont or Bevan? on the phone) mentioned HSI is an unlikely problem.

What are my options here?

1. Take the airplane to avionics shop to diagnose the issue (most logical step...)

2. Send the KX-165 for evaluation/repairs (and possibly the HSI)

3. Apply more elbow grease and then retreat to option #1 or #2

You might consider correcting  the title of your post. KI-525 is a King HSI. 252 is a Mooney model.

[PeterRus]

23 hours ago, OR75 said:

any option to borrow a 165 (or 155) to test ?

I have a 155 (no GS) paired with a CDI KI-202 or something similar as COM2/NAV2. Are 155 and 165 interchangeable? I know that there is two coax connectors on the back of 155 and three on the back of the 165 and 165 has one more blade/slot connector. 

[GMBrown]

Ed at https://www.kx-155.com may be making new displays for the 155. You can reach him at email at "ED@KX-155.com" or at the phone numbers on his website. 

If the 165 uses the same display, you might find what you're looking for with Ed. I bought a like new 155 from him. works great.

[vik]

On 8/25/2024 at 8:36 AM, PeterRus said:

Are 155 and 165 interchangeable?

No, KX-165 has a built in VOR converter, while KX-155 requires a CDI with a VOR converter.

[PeterRus]

Closure on the topic: sent the kx165 to Bevan and they fixed it replacing about 200 (ballpark estimate) capacitors. Flew it today and all works. Many thanks to Jake@BevanAviation and other wonderful people at Bevan who answered my questions. 

Edited October 12 by PeterRus