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Radio static occurs when landing light is turned off

jasong

By jasong
in General Mooney Talk

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jasong Enthusiast

jasong

Posted
Posted

So this one has both me and our avionics guy really kind of confused.  We've been chasing some radio static that appears to somehow electrical in nature.  We assume this because at random intervals along with the static the in-panel clock blinks/flashes/resets (see video below).  Although we haven't put a ton of time into chasing down the problem I noticed yesterday that the static (and the clock flashing/resetting/blinking) stops when the landing light is turned ON.

 

Does this make sense to anyone?

 

StevenL757 Grand Master

StevenL757

Posted
Posted

So this one has both me and our avionics guy really kind of confused.  We've been chasing some radio static that appears to somehow electrical in nature.  We assume this because at random intervals along with the static the in-panel clock blinks/flashes/resets (see video below).  Although we haven't put a ton of time into chasing down the problem I noticed yesterday that the static (and the clock flashing/resetting/blinking) stops when the landing light is turned ON.

 

Does this make sense to anyone?

 

http://youtu.be/_Nhxve6Bi_8

Jason...a few questions to clarify:

- Did you have any new wiring or hardware installed recently (landing lights, etc.)?

- Were any changes made to existing wiring or hardware?

- If yes to either, did the new or modified wiring get grounded, and if so, to what?

- Are your landing and taxi lights LED, HID, or the high-draw, "standard" incandescent type (GE4509)?

Regards, Steven

ShermAv8tor Enthusiast

ShermAv8tor

Posted
Posted

so the landing light getting turned on means there is a current draw, so the static stops (or weakens enough to not hear it) due to this electrical loss off the bus. The clock seems to be completely losing power, but usually static is due to bad antenna bonding to the airframe or a loose ground wire somewhere and in this case most likely in the clock circuit. At least thats where I would start. 

jasong Enthusiast

jasong

Posted
  • Author
Posted

Jason...a few questions to clarify:

- Did you have any new wiring or hardware installed recently (landing lights, etc.)?

- Were any changes made to existing wiring or hardware?

- If yes to either, did the new or modified wiring get grounded, and if so, to what?

- Are your landing and taxi lights LED, HID, or the high-draw, "standard" incandescent type (GE4509)?

Regards, Steven

 

Steven, we had our landing light replaced (with an incandescent one while we wait for our LED to be delivered) last week, but the static existed before that.  I'm not sure however if the static disappeared when the old landing light was turned on.  Otherwise I don't think the static coincided with any other changes/modifications/installs

jasong Enthusiast

jasong

Posted
  • Author
Posted

so the landing light getting turned on means there is a current draw, so the static stops (or weakens enough to not hear it) due to this electrical loss off the bus. The clock seems to be completely losing power, but usually static is due to bad antenna bonding to the airframe or a loose ground wire somewhere and in this case most likely in the clock circuit. At least thats where I would start. 

Thanks Sherman - I was thinking the same originally, but now that the clock seems normal with the landing light on I wasn't sure if it might still be the culprit

Yetti Grand Master

Yetti

Posted
Posted

The landing light is kicking in the voltage regulator and then making the alternator kick on. Otherwise when the alternator is not on, there is something trying to ground that is not grounded.  Remove any 12volt USB or other plug in type devices and see if the static goes away.  

 

Could be voltage regulator

Does it go away at higher RPM?

Could be the shield on the P leads to your mags

Marauder Grand Master

Marauder

Posted
Posted

I have been battling a background noise demon as well. Mine has been a sizzling bacon punctuated with strobe noise. Most of the time, mine is quiet and it appears to be only triggered when I use the PTT. Then it stays around for the remainder of the flight. The noise can be heard only when a radio transmits or receives and it will do it on both radios. The plane is in for the annual and I am having him go through all of the grounds for the masters and to look at the PTT. 

Marauder Grand Master

Marauder

Posted
Posted

All - seems to get worse with higher RPM and we don't have anything plugged into any of the aux power outlets

 

Try pulling the ALT Field breaker while it is doing it. See if taking the alternator offline makes it go away. You may be dealing with a problem with the alternator.

Yetti Grand Master

Yetti

Posted
Posted

diode in alternator has gone south or my 75 F has a capacitor and a noise reduction box on the starboard firewall that I have not traced.   you may want to check that capacitor/ noise reduction filter

jasong Enthusiast

jasong

Posted
  • Author
Posted

Looks like this is definitely an alternator or voltage regulator issue.  I had my CFI checkride on Wednesday and the ammeter was going nuts most of the time, showing both positive and negative charges (mostly negative), so hopefully we've found the ultimate culprit.

carusoam Grand Master

carusoam

Posted
Posted

JG,

See if you can update some details in your avatar. It is helpful for people trying to help you out...

How did the check ride go? Or did the electrical system delay the check ride?

Best regards,

-a-

jasong Enthusiast

jasong

Posted
  • Author
Posted

JG,

See if you can update some details in your avatar. It is helpful for people trying to help you out...

How did the check ride go? Or did the electrical system delay the check ride?

Best regards,

-a-

What should I update?

 

Fortunately both the plane and I made it through the checkride :)

  • Like 1
ShermAv8tor Enthusiast

ShermAv8tor

Posted
Posted

Another thought, I don't know what year Mooney you have, but the earlier birds that came with generators and then converted to alternators face an additional challenge in the wiring for noise. The wiring in the earlier Mooneys w/ GEN did not have wiring installed that was well insulated like the Mooneys that came with alternators, and this sometimes induces noise all by itself on the conversion. The non shielded wiring picks up the static and induces it into the systems. Shields and grounds........

carusoam Grand Master

carusoam

Posted
Posted

JG,

For improved recommendations...,

It helps to have what Mooney you fly and which State you fly in. (As Sherm has indicated above)

A picture will help other MS people remember you and or your situation.

Trying to remain in cogneto is too challenging...

You can click on your avatar (picture area) then select the button 'edit my profile'.

Best regards,

-a-

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