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troubleshooting overvoltages

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hhobbit

Joined: 26 May 2011
Posts: 5

Posted: Sun Jun 19, 2011 4:40 pm Post subject: troubleshooting overvoltages

Say you've fried a transponder for no apparent reason.  So it gets fixed, at a cost.  Now putting it back in and hoping for the best doesn't seem particularly bright.  I wonder if general info on troubleshooting this sort of problem has been published anywhere, and would really appreciate any advice or links available.

nuckolls.bob(at)aeroelect
Guest

Posted: Sun Jun 19, 2011 7:09 pm Post subject: troubleshooting overvoltages

At 08:40 PM 6/19/2011, you wrote:

 	  Quote: 	
		  



Say you've fried a transponder for no apparent reason.  So it gets 

fixed, at a cost.  Now putting it back in and hoping for the best 

doesn't seem particularly bright.  I wonder if general info on 

troubleshooting this sort of problem has been published anywhere, 

and would really appreciate any advice or links available.


	




   What parts were damaged? Did the repairing service

   offers some hypothesis as to what happened? Is your

   airplane fitted with overvoltage protection?



   Bob . . .

hhobbit

Joined: 26 May 2011
Posts: 5

Posted: Mon Jun 20, 2011 5:25 am Post subject: Re: troubleshooting overvoltages

Bob

Dont know for sure until it goes back for repair.   I phoned the Mendelssohn repair shop and they tell me that the Bendix King KT76C is rarely a victim of overvoltage. There is a fuse marked LF 7A in near the edge connector which is supposedly the first item to blow; it tested ok for continuity without removing it from the board.  Further in there is a crowbar device which I am informed cannot be tested in place, at least one end must be desoldered.   I don't want to disturb that because I don't have conformal coating product to reinstate it in.  One might reasonably go on the assumption that the fuse would protect from an overvoltage? or not?  In either case the crowbar device should.  I am awaiting further communication from another repair shop which should help decide that.  Seems the circuit breaker was too lazy to do its job then 



There are four unallocated circuit breakers on the aircraft wiring diagram with rating values of 3, 6, 8 and 10A.  Until I am back at the plane which is 40 odd miles away, I wont be able to determine if its connected to the 3A breaker which would be the correct one for a 1.6A transponder maximum load.  BTW aircraft is a CTSW.

Last edited by hhobbit on Mon Jun 20, 2011 5:32 am; edited 1 time in total

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Mon Jun 20, 2011 5:28 am Post subject: Re: troubleshooting overvoltages

 	  Quote: 	
		  Say you've fried a transponder for no apparent reason. 	




Dear H. Hobbit,



Please furnish us AeroListers with a reasonably good schematic.



Together, we eclipse the combined intelligence of the Krell Empire....

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_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

l_luv2_fly(at)yahoo.com
Guest

Posted: Mon Jun 20, 2011 6:15 am Post subject: troubleshooting overvoltages

Perhaps even the known universe

do not arhive



From: Eric M. Jones <emjones(at)charter.net>

To: aeroelectric-list(at)matronics.com

Sent: Monday, June 20, 2011 8:28 AM

Subject: Re: troubleshooting overvoltages

--> AeroElectric-List message posted by: "Eric M. Jones" <emjones(at)charter.net (emjones(at)charter.net)>



 	  Quote: 	
		   Say you've fried a transponder for no apparent reason.


	


Dear H. Hobbit,

Please furnish us AeroListers with a reasonably good schematic.



Together, we eclipse the combined intelligence of the Krell Empire....

--------

Eric M. Jones

[url=http://www.PerihelionDesign.com][/url]



 [quote][b]

nuckolls.bob(at)aeroelect
Guest

Posted: Mon Jun 20, 2011 7:05 am Post subject: troubleshooting overvoltages

At 08:25 AM 6/20/2011, you wrote:

 	  Quote: 	
		  



Bob

Dont know for sure until it goes back for repair.   I phoned the 

Mendelssohn repair shop and they tell me that the Bendix King KT76C 

is rarely a victim of overvoltage. There is a fuse marked LF 7A in 

near the edge connector which is supposedly the first item to blow; 

it tested ok for continuity without removing it from the 

board.  Further in there is a crowbar device which I am informed 

cannot be tested in place, at least one end must be desoldered.   I 

don't want to disturb that because I don't have conformal coating 

product to reinstate it in.  One might reasonably go on the 

assumption that the fuse would protect from an overvoltage?


	


    Actually, the Transorb is the 'protective' device.

    The upstream fuse offers a means by which the

    circuit may be broken if the antagonistic transient

    duration is too long (like runaway alternator).



 	  Quote: 	
		    or not?  In either case the crowbar device should.


	


    Yes, if there was a power transient event, one would

    reasonably expect the transorb to stand off the event

    until (1) the even ends or (2) the fuse blows.



 	  Quote: 	
		     I am awaiting further communication from another repair shop 

 which should help decide that.  Seems the circuit breaker was too 

 lazy to do its job then [Evil or Very Mad]


	


    Circuit breakers are not ov protection devices any

    more than fuses. They become part of an ov protection

    system when combined with crowbar ov protection

    devices like our OVM series devices . . . Transorbs

    must be combined with fuses which are 10 to 100 times

    FASTER than breakers. It's a rather common misconception

    that fuses and breakers in the power distribution

    system are protection for ov events. The only service

    they perform is to protect wires from severe overload

    along with isolating a fault such that it does not

    affect the rest of the airplane.



    If your fuse is intact, then perhaps there was

    no OV event. The transponder may have simply

    suffered a failure of a venerable component.

        Bob . . .

                    ////

                   (o o)

    ===========o00o=(_)=o00o=========

    < Go ahead, make my day . . .   >

    < show me where I'm wrong.      >

    =================================

Eric M. Jones

Joined: 10 Jan 2006
Posts: 565
Location: Massachusetts

Posted: Mon Jun 20, 2011 7:44 am Post subject: Re: troubleshooting overvoltages

Make sure you understand the difference between Transorbs and MOVs.



They do approximately the same thing, but MOVs are rarely used anymore  because they have an inherent wearout mechanism. So over time, they tend to age...then fail short.



Ask the service tech for the part ID.

_________________
Eric M. Jones
www.PerihelionDesign.com
113 Brentwood Drive
Southbridge, MA 01550
(508) 764-2072
emjones(at)charter.net

hhobbit

Joined: 26 May 2011
Posts: 5

Posted: Wed Jun 22, 2011 1:43 pm Post subject: Re: troubleshooting overvoltages

Has anyone here got a usb oscilloscope? the type that turns a laptop or notebook pc into a storage scope?    If you have one, it would be great to find out what are the important specs for such a device.  They are on ebay starting at suspiciously cheap $50.  I figure on recording for example start up voltage transients in the vicinity of the starter, alternator and regulator.  Using such a device,  the intention is to eliminate a lot of theorising .   The manufacturer tells me there is no history of this kind of trouble, and if there is a rogue regulator or capacitor this could be a definitive way to diagnose.   My original question on this forum was for general information on how to go about solving such a problem.

BTW I found an interesting general article on ESD: http://www.eib-gmbh.de/englisch/faqs/text_faqs.htm in particular Q13.

nuckolls.bob(at)aeroelect
Guest

Posted: Wed Jun 22, 2011 4:14 pm Post subject: troubleshooting overvoltages

At 04:43 PM 6/22/2011, you wrote:

  	  Quote: 	
		  --> AeroElectric-List message posted by: "hhobbit" <jm2833530(at)gmail.com>



 Has anyone here got a usb oscilloscope? the type that turns a laptop or notebook pc into a storage scope?    If you have one, it would be great to find out what are the important specs for such a device.  They are on ebay starting at suspiciously cheap $50.  	


   Every one of those products will perform as advertised . . .

   and in many cases, ANY 'scope is better than NO 'scope.

   Be wary of the ratings. Know that "samples per second"

   is related to but separate from "bandwidth." For

   example:



  http://tinyurl.com/6b6lytn 



   is advertised as a 200 mHz bandwidth and 250 mega-samples

   per second. In general, sample rates should be AT LEAST 3x the

   period of interest. So 250 m-s/S implies a useful bandwidth

   on the order of 80 mHz . . . which is respectable for a

   $350 digital 'scope. But really 'clean' paints of wave-forms

   will be limited to 25 mHz.



   My Tektronix digital scope is rated at 100 mHz bandwidth

   and 1000 m-s/Sec.  Or 10x the rate of the signal of

   interest. This means that 100 mHz displayed wave-forms will

   be very faithful to reality a compared with a device

   that is only 3x faster.



   Your search for electrical gremlins needs to capture

   transients of 100 nanoseconds or longer. Shorter transients

   are easily shunted off by the capacitors that are

   invariably part of every piece of electronics. Looking

   for these little short duration spikes is always disappointing.

   But to get a good picture of a 100 nS event, you're looking

   for samples at 20nS intervals which is 50 megasamples/S.



   So the 'scope described in the link above would suffice.



 

 

   Bob . . .    [quote][b]

enginerdy(at)gmail.com
Guest

Posted: Wed Jun 22, 2011 6:51 pm Post subject: troubleshooting overvoltages

I have a Rigol 1052E... it has 50MHz bandwidth and 1GS/s (gigasample per second) when using one channel and 500MS/s when using both channels. If you're feeling brave, it can be hacked up to 100MHz bandwidth. Around $400. It has some drawbacks, but it's pretty great for the price.



http://www.tequipment.net/RigolDS1052E.html

Another option is the DSO Nano v2. It's more of a toy, but a lot cheaper. $99

http://www.sparkfun.com/products/10244



With both you should be able to save images of your captures. The first exceeds Bob's advice, the second doesn't really come close.

On Jun 22, 2011, at 4:43 PM, hhobbit wrote:



 	  Quote: 	
		   

 

 Has anyone here got a usb oscilloscope? the type that turns a laptop or notebook pc into a storage scope?    If you have one, it would be great to find out what are the important specs for such a device.  They are on ebay starting at suspiciously cheap $50.  I figure on recording for example start up voltage transients in the vicinity of the starter, alternator and regulator.  Using such a device,  the intention is to eliminate a lot of theorising .   The manufacturer tells me there is no history of this kind of trouble, and if there is a rogue regulator or capacitor this could be a definitive way to diagnose.   My original question on this forum was for general information on how to go about solving such a problem.

 BTW I found an interesting general article on ESD: http://www.eib-gmbh.de/englisch/faqs/text_faqs.htm in particular Q13.

ainut(at)knology.net
Guest

Posted: Thu Jun 23, 2011 4:24 am Post subject: troubleshooting overvoltages

Be advised.  the DSO unit is made and is shipped from China.

David

Daniel Hooper wrote:

 	  Quote: 	

 I have a Rigol 1052E... it has 50MHz bandwidth and 1GS/s (gigasample per second) when using one channel and 500MS/s when using both channels. If you're feeling brave, it can be hacked up to 100MHz bandwidth. Around $400. It has some drawbacks, but it's pretty great for the price.

 http://www.tequipment.net/RigolDS1052E.html

 Another option is the DSO Nano v2. It's more of a toy, but a lot cheaper. $99

 http://www.sparkfun.com/products/10244

 With both you should be able to save images of your captures. The first exceeds Bob's advice, the second doesn't really come close.

 On Jun 22, 2011, at 4:43 PM, hhobbit wrote:

> 

>

> Has anyone here got a usb oscilloscope? the type that turns a laptop or notebook pc into a storage scope?    If you have one, it would be great to find out what are the important specs for such a device.  They are on ebay starting at suspiciously cheap $50.  I figure on recording for example start up voltage transients in the vicinity of the starter, alternator and regulator.  Using such a device,  the intention is to eliminate a lot of theorising .   The manufacturer tells me there is no history of this kind of trouble, and if there is a rogue regulator or capacitor this could be a definitive way to diagnose.   My original question on this forum was for general information on how to go about solving such a problem.

> BTW I found an interesting general article on ESD: http://www.eib-gmbh.de/englisch/faqs/text_faqs.htm in particular Q13.

>

>

>      

-- 

If you're an American, just say NO to the Obamanation, to socialism, and get rid of Soros.

..democracy and a republic can function only in a firm partnership with morality and religion. -- John Adams.  Indeed.  Same should be said for ANY type of gubmnt

hhobbit

Joined: 26 May 2011
Posts: 5

Posted: Thu Jun 23, 2011 6:58 am Post subject: Re: troubleshooting overvoltages

Sheesh Ainut, why dont you tell your speech outside any WalMart and get your countrymen on your side?  Not every pilot is a Republican!!!

 



Great derail try BTW!

enginerdy(at)gmail.com
Guest

Posted: Thu Jun 23, 2011 11:07 am Post subject: troubleshooting overvoltages

You've got that a little turned around. If you order the Rigol from

tequipment.net, it will ship directly from China, like mine did. Rigol

is a Chinese company, and makes decent products for people on a tight

budget. The only issue I had was the foreign power plug that came with

it. I substituted a spare US IEC cable (a computer power cord) and was

up and going quickly.



The DSO (which I've never used) may be made in China, but Sparkfun is

in Boulder, CO -- to the best of my knowledge everything they sell

ships from there.



Both sparkfun and tequipment.net are companies I've bought from in the past.



On Thu, Jun 23, 2011 at 7:14 AM, David <ainut(at)knology.net> wrote:

 	  Quote: 	
		   



 Be advised.  the DSO unit is made and is shipped from China.



 David

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