Strange Electrical Problem

[takair]

7 hours ago, Guitarmaster said:

I agree it has to be stray voltage... however, what I don't get is why it goes away when the stall vane is grounded.  I would think it would have the opposite affect and get louder.

I have a clock a KLN89 and MX170C radios.  This problem started about three months ago.  The crackle/sizzle goes on indefinitely.  I have left it for multiple days with no noticeable depletion of the battery.  I don't use a battery minder.

I have inspected all the wiring and can't find any evidence of chafing.

It goes away when you hit the switch because it is shunting this stray voltage fully to ground and it does not have enough current to activate the alert in the normal and proper fashion.  It could be a strange ground loop too, but I would think that you would then require a ground that was partial.  There is some voltage getting onto one of the wires to to the alert.  If it were a wire in proximity, I would think it would need to be fairly high current and your battery would run down.

[Yetti]

9 hours ago, Guitarmaster said:

I agree it has to be stray voltage... however, what I don't get is why it goes away when the stall vane is grounded.  I would think it would have the opposite affect and get louder.
 

Bing Bing you answered your own question.    I would say that something else has lost their ground and is seeking ground through your sonalerts/stall circuit.  What that something else is you might be able to find by disconnecting the sonealert and seeing what stops working.   It also maybe the vane circuit has lost ground out on the wing.

[Guitarmaster]

Here's a mid-diagnostic update...

I finally got the headliner all the way off and now have free access to the Sonalert.  It IS showing system voltage. I'm not sure why I couldn't get a reading on it yesterday.  Probably just tired.  Clearly there is a problem here.  The next thing is to disconnect the Sonalert and measure the amp draw...

Stay tuned folks!

Edited March 4, 2016 by Guitarmaster

[Yetti]

I am wondering if since the light(and clock) is powered up all the time if they would leave the stall horn powered all the time.     Also technically you have a test circuit that could have gone off course.

Noticing last night my POH only covers 30 serial numbers.  The 75s are the transition the J model.  Seems like they were a test bed for some the things that went into the J.

[Guitarmaster]

58 minutes ago, Yetti said:

I am wondering if since the light(and clock) is powered up all the time if they would leave the stall horn powered all the time.     Also technically you have a test circuit that could have gone off course.

Noticing last night my POH only covers 30 serial numbers.  The 75s are the transition the J model.  Seems like they were a test bed for some the things that went into the J.

YEs.  That is true about the '75.  Maxwell told me that.  

[Guitarmaster]

Update...

The ground wire, the one to the vane, is showing 12v potential.  If I close the vane it zeros out as it should.  When released it returns to ~12V.  When I turn the master on, the potential goes to zero.  About 30 seconds after turning the master off, the ground wire returns to ~12v.  The meter is connected to ground and the (-) wire from the Sonalert which goes to the vane.  The (+) wire shows zero volts as it should with the master off.

Every other system I have tested, test normal.  

Edited March 4, 2016 by Guitarmaster

[yvesg]

Do this with the master off: Disconnect the minus wire from the transducer and measure the resistance between the wire that you disconnected and the ground. It should read infinite with the vane not actuated. If not, you need to disconnect at the vane and measure again. If it is infinite, the vane is probably the culprit. If it is not infinite, your wire is touching something in between that it should not.

Yves

[Marauder]

Update...

The ground wire, the one to the vane, is showing 12v potential.  If I close the vane it zeros out as it should.  When released it returns to ~12V.  When I turn the master on, the potential goes to zero.  About 30 seconds after turning the master off, the ground wire returns to ~12v.  The meter is connected to ground and the (-) wire from the Sonalert which goes to the vane.  The (+) wire shows zero volts as it should with the master off.

Every other system I have tested, test normal.  

Polarities correct?

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[Guitarmaster]

Thanks for all your inputs!!  

I did the chant and dance properly this time and the problem is gone!

Well, actually, I traced the problem to the cannon plug.  I figured if there was anyplace current would leak, that would be it.  I pulled it apart and there was a SMALL amount of corrosion in there.  Sprayed it with DeOxit, plugged and unplugged a few times and the problem seems to be solved!!  MAJOR happy dance!!

Edited March 4, 2016 by Guitarmaster

[kortopates]

Great news and I think you got lucky! Was this a cannon plug by the sonalerts or elsewhere?

[Mooneymite]

Which cannon plug?

[Marauder]

Just now, Guitarmaster said:

Thanks for all your inputs!!  

I did the chant and dance properly this time and the problem is gone!

Well, actually, I traced the problem to the cannon plug.  I figured if there was anyplace current would leak, that would be it.  I pulled it apart and there was a SMALL amount of corrosion in there.  Sprayed it with DeOxit, plugged and unplugged a few times and the problem seems to be solved!!  MAJOR happy dance!!

Was this the connector under the panel? One of the big black ones? They need special chants.

[Guitarmaster]

Just now, Guitarmaster said: Thanks for all your inputs!!  

I did the chant and dance properly this time and the problem is gone!

Well, actually, I traced the problem to the cannon plug.  I figured if there was anyplace current would leak, that would be it.  I pulled it apart and there was a SMALL amount of corrosion in there.  Sprayed it with DeOxit, plugged and unplugged a few times and the problem seems to be solved!!  MAJOR happy dance!!

Was this the connector under the panel? One of the big black ones? They need special chants.

You know Chris, you could have clued me into this a little bit earlier!

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[Marauder]

Just now, Guitarmaster said: Thanks for all your inputs!!   I did the chant and dance properly this time and the problem is gone!

Well, actually, I traced the problem to the cannon plug.  I figured if there was anyplace current would leak, that would be it.  I pulled it apart and there was a SMALL amount of corrosion in there.  Sprayed it with DeOxit, plugged and unplugged a few times and the problem seems to be solved!!  MAJOR happy dance!!

Was this the connector under the panel? One of the big black ones? They need special chants.

You know Chris, you could have clued me into this a little bit earlier!

Sent from my XT1254 using Tapatalk

I had to learn the hard way. Just sharing the love brother!

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[Guitarmaster]

Which cannon plug?

It was the Canon plug specifically for the headliner. It's physically located down by the pilot's feet.

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[carusoam]

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