Irritating Whine in Com #1 but not #2?

Jhernandez04

Jhernandez04

Line Up and Wait
Joined
Jul 13, 2012
Messages
955
Location
Arlington
Display Name
Display name:
TheHulk
Hello my friends. I have a question for those of you who are mechanically (or radio) inclined.

I recently got my plane out of the shop for a few small MX issues. An altenator belt change, postion lights not working and a some other non pressing items.


After I got my plane back with a new altenator belt and my position lights working properly I took the plane up on a short (1hr) XC flight and was having trouble hearing tower and FF. Its a very irritating whine that continues until somone keys their mic and sometimes even when they are talking. When I was at 6,500ft it would subside a little but the quality of audio was severly diminished and just when I would think the whine stopped I'd have to switch frequencies and it would be just as bad as before. Comm #2 however would not have this wine at all, but it had slightly worse reception then com #1.


Com #1 is a KX 155 w/GS
Com #2 is a KX170B w/KI 209 Indicator
Audio Panel is KMA 20 TSO

Please advise, I have been following the other Com thread about replacing for a decent price and wouldnt mind going that route but both of my radios have NAV on them.
 
In all likelihood, you had a filter capacitor on the alternator that got damaged, or removed.
 
SCCutler said:
In all likelihood, you had a filter capacitor on the alternator that got damaged, or removed.
Click to expand...


The belt was just replaced due to normal wear and tear, I did it because I wanted a new one on there before I take the wife up, how could a filter capacitor get damaged?

And how much is a fix or replace?
 
The capacitor is a cheap fix.

Pull the cowl and inspect all the wiring on the alternator - you're looking for a broken wire. If your mechanic is willing to inspect & sign-off you can replace/repair yourself. It's good to develop that kind of relationship with an A&P. Even paying for the repair it should only be $100 or so.
 
Clark1961 said:
The capacitor is a cheap fix.

Pull the cowl and inspect all the wiring on the alternator - you're looking for a broken wire. If your mechanic is willing to inspect & sign-off you can replace/repair yourself. It's good to develop that kind of relationship with an A&P. Even paying for the repair it should only be $100 or so.
Click to expand...


Yea my A/P is cool like that. I think its his fault though as it was not doing this until he fixed those items.
 
The last whine I had went away when I pushed PILOT ISOLATE on the intercom :)
 
Ron,

I LOVE that button... best way to shut the wife and kids up.. Although, my A20 cancels noise so well, i can still hear them talking.
 
sferguson524 said:
Ron,

I LOVE that button... best way to shut the wife and kids up.. Although, my A20 cancels noise so well, i can still hear them talking.
Click to expand...

I've found that it doesn't really shut them up - it just stores the noise until you land and get out of the plane - then you get all that stored up noise directed at you in one long angry burst.
 
edessa said:
I wouldn't say its his fault until you know for sure that he caused it. It could be that you just have a new problem.
Click to expand...


Good point. I wouldn't ever tell him that though. Unless it was negligent.

hopefully it's an easy fix. Because talking to ff is getting frustrating when I have to hear the bs whine....
 
Does this wine increase. And decrease in frequency with engine RPM changes ?.

If so you may have an alternator problem developing. A worn bearing or worn brushes might show up more after a new belt is installed since it would likely have more tension on it than the old one. This increase the side load on the armature , bearings and brushes. In other words it may be talking to you and telling you it is about to take a dump.
 
Vaflier said:
Does this wine increase. And decrease in frequency with engine RPM changes ?.

If so you may have an alternator problem developing. A worn bearing or worn brushes might show up more after a new belt is installed since it would likely have more tension on it than the old one. This increase the side load on the armature , bearings and brushes. In other words it may be talking to you and telling you it is about to take a dump.
Click to expand...


No its only in com 1. RPM has zero effect on the whine.
 
Jhernandez04 said:
No its only in com 1. RPM has zero effect on the whine.
Click to expand...

If it is only in com1 and rpm has zero effect, the odds of it being an alternator problem are near zero also. Do me a favor one more time and tell me ALL about the whine. When it does it, what makes it stop, and so forth.

Jim
 
weirdjim said:
If it is only in com1 and rpm has zero effect, the odds of it being an alternator problem are near zero also. Do me a favor one more time and tell me ALL about the whine. When it does it, what makes it stop, and so forth.

Jim
Click to expand...



It whines as soon as you turn it on but even worse when the mic is keyed. It comes and goes at altitude. It's almost like my antennas are messed up. But com2 has really bad reception.

Some static also.
 
Have you noticed it with the engine off? If not, start the engine, listen for the whine and start pulling circuit breakers until it goes away. If it doesn't after all breakers are pulled then its your radio.
 
Jhernandez04 said:
It whines as soon as you turn it on but even worse when the mic is keyed. It comes and goes at altitude. It's almost like my antennas are messed up. But com2 has really bad reception.

Some static also.
Click to expand...

Can you take the time to fully describe what is happening so that I can start to sort out the possibilities?

Jim
 
Jhernandez04 said:
I'm sorry but there's nothing else that I haven't mentioned.
Click to expand...

I'm sorry too, because from the way you describe it, it is not a solvable problem. Anybody can wild-@$$ guess solutions, but if you want help that won't send you scattering all over the map, I'd suggest that you get a friend that has a little better skills in defining what is going on and then perhaps we can use a little logic and deduction helping you.

Jim
 
weirdjim said:
I'm sorry too, because from the way you describe it, it is not a solvable problem. Anybody can wild-@$$ guess solutions, but if you want help that won't send you scattering all over the map, I'd suggest that you get a friend that has a little better skills in defining what is going on and then perhaps we can use a little logic and deduction helping you.

Jim
Click to expand...


Thanks for the help.
 
Jhernandez04 said:
I'm sorry but there's nothing else that I haven't mentioned.
Click to expand...

Hulk, Do you have stobe lights and if so were they turned on or off. Seems as though they will often give a backgrouns whine that is very annoying to me. Just a thought.

Randy
 
weirdjim said:
Don't mention it. Learn how to ask for help and maybe you will get back good information.

Jim



.
Click to expand...


Yea I guess making a thread and explaining what I'm hearing isn't asking for help. Either you can offer your assistance or keep your condescending comments to yourself.


Thanks, once again.
 
Vaflier said:
Hulk, Do you have stobe lights and if so were they turned on or off. Seems as though they will often give a backgrouns whine that is very annoying to me. Just a thought.

Randy
Click to expand...



Yes sir I do have strobes. I've used them during my most recent night flight (January) and the radio was fine, although it wouldn't hurt to check them again.
 
Jhernandez04 said:
Yea I guess making a thread and explaining what I'm hearing isn't asking for help. Either you can offer your assistance or keep your condescending comments to yourself.
Thanks, once again.
Click to expand...

Lissen, sir. I started in this business when I was 15 fixing radios in return for flight time, graduated to engineering Apollo and then wound up with a wonderful business for the last 40 years in the avionics engineering and manufacturing business.

I've suffered more jerknoses than you in this biz and I don't need another one. You expect hundreds of dollars engineering time fixing your problem and aren't willing to spend ten minutes trying to explain the problem. Good luck.

I hope you spend a thousand dollars solving your problem because you refuse to give us the information necessary to figure out what is wrong. You are on your own.

Take your problem and spend your money, but don't bother us any more.

THanks,

Jim
 
Well. It seems like the most likely culprit is the filter capacitor on the back of the alternator, it could have been hit with a wrench while loosing the bolts and installing the new belt. Let us know what you find . Best of luck.

Randy
 
Vaflier said:
Well. It seems like the most likely culprit is the filter capacitor on the back of the alternator, it could have been hit with a wrench while loosing the bolts and installing the new belt. Let us know what you find . Best of luck.

Randy
Click to expand...

So tell us why you think this would affect #2 without affecting #1?

Thanks,

Jim
 
I was idly wondering if it is remotely possible that the affected radio was on a step-up power supply (14 to 28 volts)? Could be power supply switching noise.
 
weirdjim said:
Lissen, sir. I started in this business when I was 15 fixing radios in return for flight time, graduated to engineering Apollo and then wound up with a wonderful business for the last 40 years in the avionics engineering and manufacturing business.

I've suffered more jerknoses than you in this biz and I don't need another one. You expect hundreds of dollars engineering time fixing your problem and aren't willing to spend ten minutes trying to explain the problem. Good luck.

I hope you spend a thousand dollars solving your problem because you refuse to give us the information necessary to figure out what is wrong. You are on your own.

Take your problem and spend your money, but don't bother us any more.

THanks,

Jim
Click to expand...

Don't bother "us" any more? What, are you and everyone else bothered by my question? If you're as experienced as you claim then I imagine you'd be able to troubleshoot my issue. I don't refuse to give you information, i've given you everything i've experienced and you come back with "give me more"...... how the hell can I give you more when all I do is press the mic and it whines even louder.

You seem mad I cant diagnose my own problem. Let me apolagize for that.....you'll be waiting a while.

If you ask specific questions then im sure a low time pilot like myself can assist someone as knowledgable as you, but it seems like you're better then me so i'll leave you and your friends alone. :rolleyes:
 
Jhernandez04 said:
Don't bother "us" any more? What, are you and everyone else bothered by my question? If you're as experienced as you claim then I imagine you'd be able to troubleshoot my issue. I don't refuse to give you information, i've given you everything i've experienced and you come back with "give me more"...... how the hell can I give you more when all I do is press the mic and it whines even louder.

You seem mad I cant diagnose my own problem. Let me apolagize for that.....you'll be waiting a while.

If you ask specific questions then im sure a low time pilot like myself can assist someone as knowledgable as you, but it seems like you're better then me so i'll leave you and your friends alone. :rolleyes:
Click to expand...

Jim is an electrical engineer who woke up on the wrong side of the bed this year. Dont let him get under your skin. You aren't paying him for anything, so you get what you paid for.

Moving on:

It may be the alternator capacitor.. the recent maintenance could be an indication of "trauma".

it could be a ground issue that is just arising, corrosion, cracked solder.

Work through the easy and cheap stuff first. Gremlins are like that.
 
weirdjim said:
So tell us why you think this would affect #2 without affecting #1?

Thanks,

Jim
Click to expand...

My guess would be that one radio may have better internal filtering than the other. Just a guess but the filter capacitor is easy to check and see if the wire is off . Wont take but a minute, and could easily have been knocked loose while adjusting the alternator belt. But then you certainly know more about such things than I do. Still it wont hurt to pop the cowl and take a look.
 
Doggtyred said:
Jim is an electrical engineer who woke up on the wrong side of the bed this year. Dont let him get under your skin. You aren't paying him for anything, so you get what you paid for.
Click to expand...

Yeah, I guess I ate too much bitchy cereal for breakfast this morning.

OK, let's sort it out.

We are only going to turn on one radio, the one that is distorted. We are going to use something like an ATIS that provides a constant signal for us to listen to. We are going to do it on the ground, engine off. We are only going to listen. Do not key the transmitter.

Is the ATIS distorted? In both headsets or only one?

If not, does it become distorted with the engine running? At idle or at cruise power ON THE GROUND.

If you don't have an ATIS have a friend talk to you FROM THE OTHER END OF THE FIELD with either his aircraft radio OR a handheld (handheld preferred).

Report results and we'll go from there.

Jim
 
weirdjim said:
Yeah, I guess I ate too much bitchy cereal for breakfast this morning.

OK, let's sort it out.

We are only going to turn on one radio, the one that is distorted. We are going to use something like an ATIS that provides a constant signal for us to listen to. We are going to do it on the ground, engine off. We are only going to listen. Do not key the transmitter.

Is the ATIS distorted? In both headsets or only one?

If not, does it become distorted with the engine running? At idle or at cruise power ON THE GROUND.

If you don't have an ATIS have a friend talk to you FROM THE OTHER END OF THE FIELD with either his aircraft radio OR a handheld (handheld preferred).

Report results and we'll go from there.

Jim
Click to expand...

That's very helpful. I will report back in a few days with the answers to your questions.

I appreciate the earnest help.
 
flyingron said:
The last whine I had went away when I pushed PILOT ISOLATE on the intercom :)
Click to expand...

Also known as the CFI isolate button. I show it to my students and tell them if they get tired of listening to me, just push the button and keep nodding in agreement.
 
and Jim's post re-enforces a position that I've held for years ... troubleshooting is a process that can be intuitive to some, taught to others, and for some ... like teaching a pig to sing*.


*Mark Twain or Robert Heinlein, depending on your search engine.
 
weirdjim said:
Yeah, I guess I ate too much bitchy cereal for breakfast this morning.

OK, let's sort it out.

We are only going to turn on one radio, the one that is distorted. We are going to use something like an ATIS that provides a constant signal for us to listen to. We are going to do it on the ground, engine off. We are only going to listen. Do not key the transmitter.

Is the ATIS distorted? In both headsets or only one?

If not, does it become distorted with the engine running? At idle or at cruise power ON THE GROUND.

If you don't have an ATIS have a friend talk to you FROM THE OTHER END OF THE FIELD with either his aircraft radio OR a handheld (handheld preferred).

Report results and we'll go from there.

Jim
Click to expand...


Here's an update.

I was finally able to get away from work for an hour and went to try the suggestions. Unfortunately they didn't have an atis and no one was around so I was limited. I'll try again to complete the suggestions.

The whine was gone with the engine off, I keyed the mic and still nothing. I turned the engine on and there was no whine, keyed mic and nothing. Switched channels, could not hear anything from anyone so I don't think this did much for diagnosis but I wanted to at least try.

It is interesting to note that I have 3 antennas and one of them was able to be turned by hand freely, I turned it slightly and it seemed to tighten, I did this before I tried the radios..... could a loose antenna be the culprit? It makes sense due to the erratic quality of the radio in flight. But I'm no expert and I can't get it checked out by a pro until I get home next week.
 
You must log in or register to reply here.
Back
Top