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KX155 noise-only

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zwakie

Joined: 03 Aug 2009
Posts: 157

Posted: Thu Sep 17, 2009 2:14 am Post subject: KX155 noise-only

Being new to maintaining and troubleshooting issues with avionics, I am kind of hoping someone can put me in the right direction to get my NAV/COM set working again.



My KX155 stopped functioning. All that I am getting now is noise in the headset. Not getting my voice echoed either. I've tried all variations for squelch and volume, on radio, headset and intercom - nothing but noise at every possible combination.



When pressing the PTT-switch, the "T" for transmitting is showing, but I can't state for a fact that it actually is transmitting (I will test that on a dummy frequency using my handheld radio as a receiver the next time at the hangar).



Does anybody have any suggestion to the most likely causes please?



Thanks.

Marcel

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zwakie

Joined: 03 Aug 2009
Posts: 157

Posted: Fri Sep 18, 2009 11:43 am Post subject: Re: KX155 noise-only

I just returned from my aircraft and tested transmission, using a handheld as a receiver.



The radio IS still transmitting, so the problem is outputting to the headset through the intercom.

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ceengland(at)bellsouth.ne
Guest

Posted: Fri Sep 18, 2009 8:12 pm Post subject: KX155 noise-only

Being new to maintaining and troubleshooting issues with avionics, I am kind of hoping someone can put me in the right direction to get my NAV/COM set working again.



My KX155 stopped functioning. All that I am getting now is noise in the headset. Not getting my voice echoed either. I've tried all variations for squelch and volume, on radio, headset and intercom - nothing but noise at every possible combination.



When pressing the PTT-switch, the "T" for transmitting is showing, but I can't state for a fact that it actually is transmitting (I will test that on a dummy frequency using my handheld radio as a receiver the next time at the hangar).



Does anybody have any suggestion to the most likely causes please?



Thanks.

Marcel



zwakie wrote:

 	  Quote: 	
		   



 I just returned from my aircraft and tested transmission, using a handheld as a receiver.



 The radio IS still transmitting, so the problem is outputting to the headset through the intercom.



   


	


Hi Marcel,



I pasted your 1st message into this one to get all the symptoms together.



What kind of noise? Is it 'white' noise like  you'd hear on an AM radio 

tuned between stations, or an old TV set to an empty channel? If so, 

does the radio's volume control have no effect on the noise volume? If 

no effect, have you checked the nav section's volume? I've actually seen 

this happen to people on a couple of occasions with combo nav/comms. The 

nav (noise) volume can overwhelm everything else in the radio.



If it's not white noise, and the nav volume is in fact turned down, and 

the comm volume is in fact turned down, is it a hum or buzz? If so, is 

it still there if you unplug your mic cord? If so, it might be that the 

audio output of the radio really does have a problem.



Charlie

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zwakie

Joined: 03 Aug 2009
Posts: 157

Posted: Sat Sep 19, 2009 12:48 am Post subject: Re: KX155 noise-only

Hi Charlie,



First of all, thanks for responding to this newbee's question!



 	  ceengland(at)bellsouth.ne wrote: 	
		  What kind of noise? 	


Very similar to what you can hear in the WAV file in this ZIP-file, yet frequency on my radio seems to be a bit lower than in this sample: Sample White Noise

So yes it is white noise.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, does the radio's volume control have no effect on the noise volume? 	


Negative. I did however notice that there was a slight drop in volume when pulling the COM kHz selector knob or the NAV IDENT knob.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If no effect, have you checked the nav section's volume? 	


Not sure if I have this checked, will do it next time at the hangar.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If it's not white noise, and the nav volume is in fact turned down, and 

the comm volume is in fact turned down, is it a hum or buzz? 	


Don't know, will check as well.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, is it still there if you unplug your mic cord? 	


Don't know either, will have to check.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, it might be that the audio output of the radio really does have a problem. 	


Let's hope we won't have to reach that conclusion  



Thanks.

Marcel

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zwakie

Joined: 03 Aug 2009
Posts: 157

Posted: Sat Sep 19, 2009 12:52 am Post subject: Re: KX155 noise-only

Come to think of it, could it be something as simple as some wiring gone loose or terminal-connection breaking up?

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ceengland(at)bellsouth.ne
Guest

Posted: Sat Sep 19, 2009 10:48 am Post subject: KX155 noise-only

Charlie England wrote:

 	  Quote: 	
		   Being new to maintaining and troubleshooting issues with avionics, I 

 am kind of hoping someone can put me in the right direction to get my 

 NAV/COM set working again.

 My KX155 stopped functioning. All that I am getting now is noise in 

 the headset. Not getting my voice echoed either. I've tried all 

 variations for squelch and volume, on radio, headset and intercom - 

 nothing but noise at every possible combination.

 When pressing the PTT-switch, the "T" for transmitting is showing, but 

 I can't state for a fact that it actually is transmitting (I will test 

 that on a dummy frequency using my handheld radio as a receiver the 

 next time at the hangar).

 Does anybody have any suggestion to the most likely causes please?

 Thanks.

 Marcel

 zwakie wrote:

> 

>

> I just returned from my aircraft and tested transmission, using a 

> handheld as a receiver.

>

> The radio IS still transmitting, so the problem is outputting to the 

> headset through the intercom.

>

>   

 Hi Marcel,

 I pasted your 1st message into this one to get all the symptoms together.

 What kind of noise? Is it 'white' noise like  you'd hear on an AM 

 radio tuned between stations, or an old TV set to an empty channel? If 

 so, does the radio's volume control have no effect on the noise 

 volume? If no effect, have you checked the nav section's volume? I've 

 actually seen this happen to people on a couple of occasions with 

 combo nav/comms. The nav (noise) volume can overwhelm everything else 

 in the radio.

 If it's not white noise, and the nav volume is in fact turned down, 

 and the comm volume is in fact turned down, is it a hum or buzz? If 

 so, is it still there if you unplug your mic cord? If so, it might be 

 that the audio output of the radio really does have a problem.

 Charlie

 	  Quote: 	
		  >Come to think of it, could it be something as simple as some wiring gone loose or terminal-connection breaking up?

Marcel,

To get help in troubleshooting, it's helpful to keep the communications (and troubleshooting steps/results) together and in sequence. If someone new sees one of the posts & wants to help, they need to see all the symptoms & what's already been tried.

One thing I forgot to mention in the previous post is to simplify the 

system. You mentioned 'problem is outputting to the headset through the 

intercom'. Have you turned off the intercom while checking? If the 

system is set up correctly, the radio should be audible through the 

pilot's headset with the intercom turned off, and you should be able to 

transmit with it off, also. With the intercom in the circuit, that's an 

extra component that could be causing your problem.

Another thing I forgot to mention that may be a really quick check, is 

to find another a/c with the same radio & swap yours into the other 

a/c's radio tray. If your radio actually has an internal problem, you'll 

get the same symptoms in the other a/c. If the problem is outside the 

radio (installation or a different component, like the intercom), then 

your radio will work normally in the other a/c.

Charlie

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zwakie

Joined: 03 Aug 2009
Posts: 157

Posted: Thu Sep 24, 2009 11:12 am Post subject: Re: KX155 noise-only

I have good news: I found the cause! 



It turned out that the nav section's volume was not completely turned to silent. The volume knob was just a fraction from being closed, so I was very surprised that this fraction totally blocked the COM audio to my headset. Valuable lesson learned.



What I would like to do next, is to find a way to minimize this effect. Any ideas?



Marcel



 	  zwakie wrote: 	
		  Hi Charlie,



First of all, thanks for responding to this newbee's question!



 	  ceengland(at)bellsouth.ne wrote: 	
		  What kind of noise? 	


Very similar to what you can hear in the WAV file in this ZIP-file, yet frequency on my radio seems to be a bit lower than in this sample: Sample White Noise

So yes it is white noise.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, does the radio's volume control have no effect on the noise volume? 	


Negative. I did however notice that there was a slight drop in volume when pulling the COM kHz selector knob or the NAV IDENT knob.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If no effect, have you checked the nav section's volume? 	


Not sure if I have this checked, will do it next time at the hangar.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If it's not white noise, and the nav volume is in fact turned down, and 

the comm volume is in fact turned down, is it a hum or buzz? 	


Don't know, will check as well.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, is it still there if you unplug your mic cord? 	


Don't know either, will have to check.



 	  ceengland(at)bellsouth.ne wrote: 	
		  If so, it might be that the audio output of the radio really does have a problem. 	


Let's hope we won't have to reach that conclusion  



Thanks.

Marcel

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