Radio BUZZZ !

Indiana_Pilot

Indiana_Pilot

Line Up and Wait
Joined
Nov 2, 2013
Messages
802
Location
Connersville, IN
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Flying "B"
I have 2 radios and they are started to pick up a "buzz" in the radios from what sounds like the magnetos but it seems as though it is not coming from just one.. I wanted your guys feedback before I head off to the Avionics Shop or A/P.. Here is what I have done to test so far..

Happens on both radios (2 different type Narco and MX-12) The MX-12 always had a little bit of engine noise in it and it seems to pick up a little static when I turn on my LED landing light on as well but now it is bad on both..

- Checked each mag individually resulting in the same sound..

- Intercom and/or audio panel off same sound..

I did have the ADF Belly antenna removed since there hasn't been a ADF in it for years.. The connector and wires still run to the rear by the battery tray. The problem seemed to happen after it was removed.

Is it possible the ADF cables (2 cables with multiple conductors inside them) are still connected to something in the panel and it's acting as an antenna for the noise?

I guess I could try and ground the connector with a jumper since it was grounded via the antenna mounting before.. but what in the world would still be connected to it ?

Thanks!
 
Firefighter_324 said:
I have 2 radios and they are started to pick up a "buzz"
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OK, we've had our fair share of these radio problems in here recently and another thread came up with a darned good idea. Record the sound (distortion, squeal, buzz, etc.) and attach it as a sound file so we at least have a fighting chance to try and figure out what it is.

Jim
 
Good idea.. I will do that.. I did however determine it is coming from the left mag (I swear I checked that before) but only happens when left mag or both is selected.. right mag makes no noise.. Mags check smooth and seem ok.. Am I looking at new wires or condenser ?


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Could be bad shielding on the p-Lead (quite possible if it is isolated to one mag). Also if switching a mag off makes it go away that largely separates it from other potential sources (like the alternator or power converters).
 
flyingron said:
Could be bad shielding on the p-Lead (quite possible if it is isolated to one mag). Also if switching a mag off makes it go away that largely separates it from other potential sources (like the alternator or power converters).
Click to expand...


My thought as well. In my opinion/experience, this would be almost definitely a shielding/ grounding problem. Since you've already determined that it's isolated to the left mag, p-lead sounds likely to me. Otherwise, check the common ground that the radios probably use, clean it, then check the antenna coax for breaks in the shielding or loose connections.


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SPAJC said:
My thought as well. In my opinion/experience, this would be almost definitely a shielding/ grounding problem. Since you've already determined that it's isolated to the left mag, p-lead sounds likely to me. Otherwise, check the common ground that the radios probably use, clean it, then check the antenna coax for breaks in the shielding or loose connections.
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All I ask ... ALL I ASK is a nickel for every time somebody tries to fix a problem by calling it a "bad ground" or "loose connection".

I could retire early.


Jim
 
After some more looking around it appears that the left mag's p lead Shield was totally pullled away from the hex nut shield and was almost pulled away from the "filter box" on the firewall. Looks like I will have to have new leads put in..
 
Huh. Look at that. A "loose connection". ;)

(of the shield anyway...)

Poking Jim. ;) ;) ;)
 
weirdjim said:
All I ask ... ALL I ASK is a nickel for every time somebody tries to fix a problem by calling it a "bad ground" or "loose connection".

I could retire early.


Jim
Click to expand...

Yet I've seen several thousands of dollars ****ed away troubleshooting a squawk when the real culprit was a wire broken at the pin, inside the back shell of a cannon plug.

I can only assume was that wire was improperly stripped, nicking too many wires, or overstressed at some point before the back shell was secured.
 
Firefighter_324 said:
After some more looking around it appears that the left mag's p lead Shield was totally pullled away from the hex nut shield and was almost pulled away from the "filter box" on the firewall. Looks like I will have to have new leads put in..
Click to expand...

Filter box on the firewall for P-leads? Can't recall seeing that. Most of that sort of thing is for the alternator.

Vibration commonly breaks P-lead shielding at the mags, and sometimes the P-leads themselves. It also breaks the field wire at the alternator and disables that system. Those are things we check at inspections for fraying.
 
Yes, they are behind a small metal box and are shaped like barrels that are built into the firewall.. So are you saying the p leads usually run from the mags all the way to the switch and then grounded back at the mag? I have had 2 different A/P tell me two different things now..


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weirdjim said:
It ain't "loose" it is BROKEN. Shielding is only good if the wires forming the shield stay intact.

Jim
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Quite pedantic. How do most people find a broken shield again? Oh yeah... Grab it and wiggle with enough force to notice it's "loose" with the outer jacket often still looking like it's intact.

I get your point Jim, really I do, but you're succumbing to the standard engineer problem of not knowing the audience.

Most normal folk are going to call a broken shield "loose". It's not wrong, to anyone but the engineer looking at it. It's just a different level of understanding for that particular sub-set of people.

You really should come do some desktop support sometime on PCs. You'd go insane trying to interpret what people mean when they're describing a computer problem if "loose" for a broken wire bothers you.

First rule of thumb: Everything, and I mean everything on the desktop is a "shortcut". I don't care if it's a zip file copied to the desktop, the average end user will call it a "shortcut". And they'll think you're an ass know-it-all if you correct them on it, even nicely. Hahaha.

C'mon over and try it in a call center sometime. It's enlightening as to why call center managers resort to writing scripts for the people to speak on the phone.

Not kidding. I had someone come up to me in a panic two weeks ago saying their login didn't work. This was a person who's job requires them not to just work on computers all day for a living but at a pretty high level. Not a developer but certainly could find their way around both spreadsheets and database access as a user.

I walked over, looked at the screen, and said, "Someone else logged into your PC last night, as I pointed to the "helpful" prompt showing that the computer had already "guessed" the username and domain name and was just waiting for the password.

The person sheepishly clicked "change user", actually typed their username in, and went about their day. They'd been looking for "help" for two hours at that point and luckily hadn't locked the OTHER user out of the Domain yet by one attempt, for bad password attempt count.

Anyway... Just be cognizant of the audience. "Loose" and "broken" are interchangeable at some level. :) I live that fun every day, and had the pedantic beat out of me by them, unless I'm talking to a certified geek. Haha.
 
So the p leads were repaired and the left mag still produced the sound.. I discovered another problem now.. I am sure this could cause the sound too?
4b29f7b90357edcf09b2b70d70eb76cd.jpg



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denverpilot said:
Anyway... Just be cognizant of the audience. "Loose" and "broken" are interchangeable at some level. :) I live that fun every day, and had the pedantic beat out of me by them, unless I'm talking to a certified geek. Haha.
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HaHa my sweet hiney. I've chased enough electrons from incomplete descriptions of the problem for a lifetime. Not going to happen.

My friends all tell me I have one major flaw (amidst dozens of minor flaws) and that is that I do not suffer fools graciously. Having been in customer service (besides being the chief engineer) and politics all of my life, that is a very significant disadvantage that I do NOT try to hide. Don't want my peaches, don't shake my tree.

Them's the rules. Take or leave it, your choice.

Jim
 
Uhhhh ya just a little.. The odd part is it was only loose like that when the engine was hot.. I am assuming the metal expanded... I never found that until I looked again after flying a few hours today... At least I have nice new p leads that needed replaced anyway!


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weirdjim said:
HaHa my sweet hiney. I've chased enough electrons from incomplete descriptions of the problem for a lifetime. Not going to happen.

My friends all tell me I have one major flaw (amidst dozens of minor flaws) and that is that I do not suffer fools graciously. Having been in customer service (besides being the chief engineer) and politics all of my life, that is a very significant disadvantage that I do NOT try to hide. Don't want my peaches, don't shake my tree.

Them's the rules. Take or leave it, your choice.

Jim
Click to expand...


That was comedy gold.

I won't derail the guy's thread and the troubleshooting process to explain, but ask why it was so funny sometime after we figure out what's up with his radios.
 
Does anyone know where I can find a replacement for this? I can find the nut but cannot find the rest of the parts.. I found something close on Spruce but even if it's the right one it's $75... Seems like the that is a little much!


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Firefighter_324 said:
Does anyone know where I can find a replacement for this? I can find the nut but cannot find the rest of the parts.. I found something close on Spruce but even if it's the right one it's $75... Seems like the that is a little much!
Click to expand...

I'd use an airplane boneyard if it was me. In Northern California (Sacramento) we use Kenny Faeth's Airplane Salvage. Kenny is very good on used parts and I doubt he'd ding you more than $5 or 10. He will also ship by US Mail to save you a few bucks.

There ought to be a boneyard somewhere near you. Anybody know of a place near this fellow?

THanks,

Jim
 
I may have an old set of wires in my hangar, what size is the nut ??. I keep them for just such occasions. They have repaired several friends wires. Do you know how to remove and replace these parts ??.. Let me know the size and I will check for you. If I have the right size you are welcome to it.
 
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