Matronics Email Lists :: View topic - S701 Contactor Failure Analysis

Matronics Email Lists
Web Forum Interface to the Matronics Email Lists

Get Email Distribution Too! FAQ Search Memberlist Usergroups Register

Profile Log in to check your private messages Log in

S701 Contactor Failure Analysis

Matronics Email Lists Forum Index -> AeroElectric-List

View previous topic :: View next topic

Author Message

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 17, 2010 6:03 pm Post subject: S701 Contactor Failure Analysis

Last year, Marty Emrath told us about the failure of a new

contactor he had purchased from B&C.  B&C replaced the contactor

but Marty was justifiably curious as to root cause of the

failure.



I offered to document a tear-down analysis and Marty sent

me the carcass. I was looking for something fun to do this

afternoon so I took the dead puppy apart.



The pictures at . . .



http://www.aeroelectric.com/Pictures/Contactors/S701_Failure_Teardown/

Are pretty much self explanatory. One thing is for certain.

This product is much more sophisticated than its ancestors

that first took to the air in a C-140.



The last picture tells the tale . . .



http://www.aeroelectric.com/Pictures/Contactors/S701_Failure_Teardown/TearDown_10.jpg



Seems the assembler wasn't really awake yet when this

device went across their work station. One coil wire

was poorly soldered to its terminal . . . the other had

no solder at all.



Thanks for sharing your experience with us Martin!



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 17, 2010 6:20 pm Post subject: S701 Contactor Failure Analysis

 	  Quote: 	
		  

The last picture tells the tale . . .



http://www.aeroelectric.com/Pictures/Contactors/S701_Failure_Teardown/TearDown_10.jpg



Seems the assembler wasn't really awake yet when this

device went across their work station. One coil wire

was poorly soldered to its terminal . . . the other had

no solder at all.


	


   Already had a comment on the analysis . . . someone noted that

   the terminals around which the coil wires are wrapped are square

   and may indeed have sharp corners.



   He reminded me of an arcane point-to-point wiring process

   for complex digital circuits called "wire wrap". This

   process used special wire, tools, sharp edged square terminal

   posts and no solder. The tools were designed to tightly

   wrap the wire around the post with enough turns, and

   stretching force to create multiple gas-tight joints

   on the corners at each connection.



   As I recall this technology called for about 6 tightly

   spaced turns around the post (24+ points of contact).

   Since this coil-form is plastic . . . and soldering these

   joints would call for considerable heat and time,

   it may well be that the original design calls for

   no solder at all.



   In this case, the assembler of the failed item was

   perhaps not in possession of the right tool. The turns

   about both posts are not those produced by a "wire wrap"

   tool. The curious thing is that there is SOME solder

   on one of the terminals . . . perhaps didn't pass a

   continuity test and the solder dab "fixed it" only to

   have the other joint fail later.



   Guess we'll have to tear down another contactor to

   see. I don't think I have one in the shop. I'll go

   buy one.



   Bob . . .

rjquillin(at)cox.net
Guest

Posted: Wed Feb 17, 2010 6:48 pm Post subject: S701 Contactor Failure Analysis

You have a good recollection.



 I just did some wire-wrap late last year.

 However, the wire used has Kynar or other insulation that is removed to expose a bare, generally tin coated, conductor.



 The wire used to wind the coil, from your pictures, appears to be 'magnet' wire which has an insulating coating.  The wire-wrap process, as I have always seen it implemented, is not designed for this type of insulated wire and is not expected to breech the insulation to form a contact.



 I believe your original diagnosis of no solder was spot-on. 



 Ron Q.



 At 18:18 2/17/2010, you wrote:

 [quote]He reminded me of an arcane point-to-point wiring process

   for complex digital circuits called "wire wrap". This

   process used special wire, tools, sharp edged square terminal

   posts and no solder. The tools were designed to tightly

   wrap the wire around the post with enough turns, and

   stretching force to create multiple gas-tight joints

   on the corners at each connection.



   As I recall this technology called for about 6 tightly

   spaced turns around the post (24+ points of contact).

   Since this coil-form is plastic . . . and soldering these

   joints would call for considerable heat and time,

   it may well be that the original design calls for

   no solder at all.[b]

Bret Smith

Joined: 09 Jan 2006
Posts: 178
Location: Mineral Bluff, GA

Posted: Wed Feb 17, 2010 7:13 pm Post subject: S701 Contactor Failure Analysis

Thank you Bob, It is always interesting to learn more about the art of

aircraft electronics.

Bret Smith

RV-9A N16BL

Blue Ridge, GA

www.FlightInnovations.com



--

_________________
Bret Smith
RV-9A (Emp)

retasker(at)optonline.net
Guest

Posted: Wed Feb 17, 2010 8:13 pm Post subject: S701 Contactor Failure Analysis

Your recollection is generally true and the same as the wire I have used 

for all the wire wrapping I have done.  However, once upon a time there 

was wire sold for wrapping that did not require stripping.  

Unfortunately, I don't remember who sold it nor do I have any.  Further, 

I seem to recall that it was not too successful as it eventually tended 

to short anywhere it overlapped under tension.

The wire on the teardown certainly looks like common magnet wire.  And 

in any case, three or four turns would certainly not be sufficient to 

make long term reliable contact in something like this which is likely 

to be exposed to rather harsh environmental conditions.  I agree with 

Bob that they just forgot to solder the wires - the operator probably 

got interrupted during assembly.

Dick Tasker

Ron Quillin wrote:

 	  Quote: 	
		   You have a good recollection.

 I just did some wire-wrap late last year.

 However, the wire used has Kynar or other insulation that is removed 

 to expose a bare, generally tin coated, conductor.

 The wire used to wind the coil, from your pictures, appears to be 

 'magnet' wire which has an insulating coating.  The wire-wrap process, 

 as I have always seen it implemented, is not designed for this type of 

 insulated wire and is not expected to breech the insulation to form a 

 contact.

 I believe your original diagnosis of no solder was spot-on.

 Ron Q.

 At 18:18 2/17/2010, you wrote:

> He reminded me of an arcane point-to-point wiring process

>   for complex digital circuits called "wire wrap". This

>   process used special wire, tools, sharp edged square terminal

>   posts and no solder. The tools were designed to tightly

>   wrap the wire around the post with enough turns, and

>   stretching force to create multiple gas-tight joints

>   on the corners at each connection.

>

>   As I recall this technology called for about 6 tightly

>   spaced turns around the post (24+ points of contact).

>   Since this coil-form is plastic . . . and soldering these

>   joints would call for considerable heat and time,

>   it may well be that the original design calls for

>   no solder at all.

 *

 *

-- 

Please Note:

No trees were destroyed in the sending of this message.  We do concede, however,

that a significant number of electrons may have been temporarily inconvenienced.

--

mauledriver(at)nc.rr.com
Guest

Posted: Wed Feb 17, 2010 8:22 pm Post subject: S701 Contactor Failure Analysis

I'm feeling old... My only hands-on experimental circuit making was pre-digital. Â  Over the years I'd pickup electronics mags and see references to "wire wrapped" terminals and never had a clue what it referred to. Â Now I get it... Thanks.



Bill



-- Sent from my Palm Pre



Ron Quillin wrote:



 You have a good recollection.



 I just did some wire-wrap late last year.

 However, the wire used has Kynar or other insulation that is removed to expose a bare, generally tin coated, conductor.



 The wire used to wind the coil, from your pictures, appears to be 'magnet' wire which has an insulating coating.Â  The wire-wrap process, as I have always seen it implemented, is not designed for this type of insulated wire and is not expected to breech the insulation to form a contact.



 I believe your original diagnosis of no solder was spot-on. 



 Ron Q.



 At 18:18 2/17/2010, you wrote:

  	  Quote: 	
		  He reminded me of an arcane point-to-point wiring process

 Â  for complex digital circuits called "wire wrap". This

 Â  process used special wire, tools, sharp edged square terminal

 Â  posts and no solder. The tools were designed to tightly

 Â  wrap the wire around the post with enough turns, and

 Â  stretching force to create multiple gas-tight joints

 Â  on the corners at each connection.



 Â  As I recall this technology called for about 6 tightly

 Â  spaced turns around the post (24+ points of contact).

 Â  Since this coil-form is plastic . . . and soldering these

 Â  joints would call for considerable heat and time,

 Â  it may well be that the original design calls for

 Â  no solder at all.

">http://www.matronics.com/Navigator?AeroElectric-List

com

tronics.com/contribution



	
    [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 17, 2010 9:33 pm Post subject: S701 Contactor Failure Analysis

At 10:22 PM 2/17/2010, you wrote:

 	  Quote: 	
		  I'm feeling old... My only hands-on experimental 

circuit making was pre-digital. Â  Over the 

years I'd pickup electronics mags and see 

references to "wire wrapped" terminals and never 

had a clue what it referred to. Â Now I get it... Thanks.



Bill


	


    see:



http://en.wikipedia.org/wiki/Wire_wrap



    This is the modern incarnation used on complex backplanes

    where gazillion-layer boards are impractical. The no-strip

    version is from way-back-when and it didn't hang around

    long.



    Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Feb 17, 2010 9:36 pm Post subject: S701 Contactor Failure Analysis

 	  Quote: 	
		  The wire on the teardown certainly looks like common magnet 

wire.  And in any case, three or four turns would certainly not be 

sufficient to make long term reliable contact in something like this 

which is likely to be exposed to rather harsh environmental 

conditions.  I agree with Bob that they just forgot to solder the 

wires - the operator probably got interrupted during assembly.


	


   Just for grins, I took a chunk of the wire off the

   failed coil and subjected it to a puddle of molten

   solder. The insulation was indeed a "solder-eze"

   type . . . you can solder through it without pre-

   stripping.



   The plastic used on the bobbin did melt at soldering

   iron temperatures but not quickly. So it seems a rational

   deduction that the failed joints were intended to be

   soldered. The right temperature and flux combination

   would have produced a reliable joint with minimal

   effect on the bobbin.



   I guess I won't go buy one to take apart . . . perhaps

   we'll get another carcass to inspect for other reasons

   one day.



   Bob . . .

tomcostanza

Joined: 19 Oct 2008
Posts: 49

Posted: Thu Feb 18, 2010 3:58 am Post subject: Re: S701 Contactor Failure Analysis

If I remember correctly, the wire-wrap technique was only for microamp level circuits; a few milliamps at the most.  I never saw any wire-wraps for the approx 1 amp that the contactor would need.  Or am I mistaken?



Clear Skies,

Tom

_________________
Clear Skies,
Tom Costanza
-- in year 17 of a 3 year project

bob(at)bob-white.com
Guest

Posted: Thu Feb 18, 2010 7:41 am Post subject: S701 Contactor Failure Analysis

I remember using the "no strip" technique many years ago.  As I recall,

the wrap tool did slit the insulation as it was wrapped around the

post so that bare wire was wrapped onto the post.



Bob W.



On Wed, 17 Feb 2010 23:30:03 -0600

"Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com> wrote:



 	  Quote: 	
		   

 

 At 10:22 PM 2/17/2010, you wrote:

 >I'm feeling old... My only hands-on experimental 

 >circuit making was pre-digital. Â  Over the 

 >years I'd pickup electronics mags and see 

 >references to "wire wrapped" terminals and never 

 >had a clue what it referred to. Â Now I get it... Thanks.

 >

 >Bill

 

     see:

 

 http://en.wikipedia.org/wiki/Wire_wrap

 

     This is the modern incarnation used on complex backplanes

     where gazillion-layer boards are impractical. The no-strip

     version is from way-back-when and it didn't hang around

     long.

 

     Bob . . . 

 

 

 

 

 

 


	




-- 

N93BD - Rotary Powered BD-4 - http://www.bob-white.com

Now Rotary Powered  Alpine 

     http://www.youtube.com/watch?v=FwceNc2ydN8

Cables for your rotary installation - http://roblinstores.com/

Speedy11(at)aol.com
Guest

Posted: Thu Feb 18, 2010 7:48 am Post subject: S701 Contactor Failure Analysis

Bob,

 That was one of the most educational episodes ever on the Aeroelectric  Connection.

 You removed some of the mystery for us.

 Thanks,

 Stan Sutterfield

 Do not archive

  [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 18, 2010 8:14 am Post subject: S701 Contactor Failure Analysis

At 05:58 AM 2/18/2010, you wrote:

 	  Quote: 	
		  

<Tom(at)CostanzaAndAssociates.com>



If I remember correctly, the wire-wrap technique was only for 

microamp level circuits; a few milliamps at the most.  I never saw 

any wire-wraps for the approx 1 amp that the contactor would 

need.  Or am I mistaken?


	


   Yes, but that was more a function of wire size and

   size of the post in the specific process. If one

   adequately understood the physics behind making

   such joints on 4-cornered posts with the appropriate

   insulation and tools, I have no doubt that this

   contactor design could exploit the process.



   Bob . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 18, 2010 8:16 am Post subject: S701 Contactor Failure Analysis

At 09:37 AM 2/18/2010, you wrote:

 	  Quote: 	
		  



I remember using the "no strip" technique many years ago.  As I recall,

the wrap tool did slit the insulation as it was wrapped around the

post so that bare wire was wrapped onto the post.


	


   Yeah . . . I recall that. It WAS a pretty specialized

   wrapping tool.



   Bob  . . .

nuckolls.bob(at)aeroelect
Guest

Posted: Thu Feb 18, 2010 8:43 am Post subject: S701 Contactor Failure Analysis

At 09:45 AM 2/18/2010, you wrote:

  	  Quote: 	
		   Bob,

 That was one of the most educational episodes ever on the Aeroelectric Connection.

 You removed some of the mystery for us.

 Thanks, 	


   My pleasure my friend . . . it's an extension

   of a number of tasks I accomplished on the TC side of the

   house for many years.



   It was frustrating to me that folks making $multi-million$

   decisions had so little knowledge of the physics that

   described the failure . . . even less on the physics

   that was proposed to fix it.



   It took me nearly 8 years to get a brake friction material

   changed on a motor that was breaking shafts due to

   a vibration that literally screamed at the most

   casual observer.



   I explored dozens of arm-chair suppositions only

   to return to the original hypothesis and proposal

   for a fix. Finally got it done but not after 

   a bucket full of money in warranty costs and 

   customer dis-satisfaction went down the drain.



   I still have a copy of a 6-page letter I wrote to the V.P.

   of Engineering describing in minute detail how the

   shafts were failing . . . delighted to receive an e-mail

   inviting me to a working lunch. Was astounded to find that

   he wanted to discuss the letter for about 2 minutes

   and talk about fishing the rest of the time . . . sigh.



   Here on the list we have a unique opportunity to

   tap the combined knowledge and experience of folks

   who's paychecks and promotions do not depend on

   smoothing the feathers of superiors that know even

   less about the problem.

  

   Bob . . .    [quote][b]

rjquillin(at)cox.net
Guest

Posted: Thu Feb 18, 2010 8:47 am Post subject: S701 Contactor Failure Analysis

At 08:14 2/18/2010, you wrote:

  	  Quote: 	
		  Yeah . . . I recall that. It WAS a pretty specialized

   wrapping tool.



   Bob  . . . 	


 Frightning;

 I still have and can locate the auto strip bit for my electric Gardner WW tool!



 Ron Q



 do not archive

     [quote][b]

bob(at)bob-white.com
Guest

Posted: Thu Feb 18, 2010 12:37 pm Post subject: S701 Contactor Failure Analysis

On Thu, 18 Feb 2010 08:42:28 -0800

Ron Quillin <rjquillin(at)cox.net> wrote:

 	  Quote: 	
		   At 08:14 2/18/2010, you wrote:

 >Yeah . . . I recall that. It WAS a pretty specialized

 >   wrapping tool.

 >

 >   Bob  . . .

 Frightning;

 I still have and can locate the auto strip bit for my electric Gardner WW tool!

 Ron Q

 do not archive

OK, I got curious.  You can still buy the thing from Digikey:

http://parts.digikey.com/1/parts/996077-tool-slit-n-wrap-manual-w-28-p184-1.html

I can't believe they are charging $232 for one of those things.  I'm

sure I didn't pay anything like that.  I might even be able to find my

old one if anybody want a real deal. 

Bob W.

-- 

N93BD - Rotary Powered BD-4 - http://www.bob-white.com

Now Rotary Powered  Alpine 

     http://www.youtube.com/watch?v=FwceNc2ydN8

Cables for your rotary installation - http://roblinstores.com/

P184-1.jpg

Description:

Filesize:

27.02 KB

Viewed:

13545 Time(s)

retasker(at)optonline.net
Guest

Posted: Thu Feb 18, 2010 2:00 pm Post subject: S701 Contactor Failure Analysis

Yeah, I know.  I recently looked to see if the OK Industry wrap/strip/unwrap tool I have was still available.  My jaw dropped when I found out the answer is yes and it costs $34.33 from Digikey!

 

 [img]cid:part1.07050000.06080202(at)optonline.net[/img]

 

 Do not archive

 

 Bob White wrote:  	  Quote: 	
		      	  Quote: 	
		  On Thu, 18 Feb 2010 08:42:28 -0800

Ron Quillin <rjquillin(at)cox.net> (rjquillin(at)cox.net) wrote:



        	  Quote: 	
		  At 08:14 2/18/2010, you wrote:

            	  Quote: 	
		  Yeah . . . I recall that. It WAS a pretty specialized

  wrapping tool.



  Bob  . . .

      	
     

Frightning;

I still have and can locate the auto strip bit for my electric Gardner WW tool!



Ron Q



do not archive

    	
   OK, I got curious.  You can still buy the thing from Digikey:

http://parts.digikey.com/1/parts/996077-tool-slit-n-wrap-manual-w-28-p184-1.html



I can't believe they are charging $232 for one of those things.  I'm

sure I didn't pay anything like that.  I might even be able to find my

old one if anybody want a real deal. 



Bob W.

moz-screenshot-2.png

Description:

Filesize:

37.83 KB

Viewed:

13540 Time(s)

emrath(at)comcast.net
Guest

Posted: Fri Feb 19, 2010 12:00 pm Post subject: S701 Contactor Failure Analysis

Bob,

Thanks for taking time to do this. Very interesting. I hope my replacement,

provided by B&C "gratis" was not manufactured on the same day...... Marty

Time: 06:03:45 PM PST US

From: "Robert L. Nuckolls, III" <nuckolls.bob(at)aeroelectric.com>

Subject: S701 Contactor Failure Analysis

Last year, Marty Emrath told us about the failure of a new contactor he had

purchased from B&C.  B&C replaced the contactor but Marty was justifiably

curious as to root cause of the failure.



I offered to document a tear-down analysis and Marty sent

me the carcass. I was looking for something fun to do this afternoon so I

took the dead puppy apart.



The pictures at . . .



http://www.aeroelectric.com/Pictures/Contactors/S701_Failure_Teardown/

Are pretty much self explanatory. One thing is for certain. This product is

much more sophisticated than its ancestors that first took to the air in a

C-140.



The last picture tells the tale . . .



http://www.aeroelectric.com/Pictures/Contactors/S701_Failure_Teardown/TearDo

wn_10.jpg



Seems the assembler wasn't really awake yet when this

device went across their work station. One coil wire

was poorly soldered to its terminal . . . the other had

no solder at all.



Thanks for sharing your experience with us Martin!



   Bob . . .

Display posts from previous:

	Matronics Email Lists Forum Index -> AeroElectric-List	All times are GMT - 8 Hours
Page 1 of 1

Jump to:

You cannot post new topics in this forum
You cannot reply to topics in this forum
You cannot edit your posts in this forum
You cannot delete your posts in this forum
You cannot vote in polls in this forum
You cannot attach files in this forum
You can download files in this forum