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08:13 Aug-18-1998
Kelly Schauf
Non destructive isolation of PC-mount Transformer short

To the forum:

Currently, I am testing a printed-circuit-board-mount transformer.
There is one primary winding and three secondary windings.
There are two powdered-iron 'E' cores that are epoxied
together around the bobbin to provide the core for the transformer.

I have a problem where the inductance and the Q of the primary coil
drop way below normal past 1500 Hz with a signal of 100millivolts AC
applied. I suspect that there is a shorted turn of wire that may be causing
this.

Generally, there is maybe 1000+ turns of wire on the transformer, and the
chances of finding a marginal short-circuit with merely a microscope and
the eyes is a 'needle-in-a-haystack' type of chance. Is there some
method that would incorporate an electrical signal that would enable me
to find a short-circuit in the primary winding?

Any and all ideas are welcome. Questions are also welcome.

Regards,

Kelly Schauf


 
07:44 Jun-28-2000
Jeff Nelson
Re: Non destructive isolation of PC-mount Transformer short r this may help you locate how far down the line the short is.



 
09:33 Jul-01-2000
Jamie Gauthier
Re: Non destructive isolation of PC-mount Transformer short In response to the TDR message post. Time Domain Reflectometer works well
but has several disadvantages. The instrument works well as long as you
have the mininum length of cable to measure. TDR's have a dead zone. This
dead zone can range from 25 to 50 feet (plus or minus depending on the
quality of your instrument.) Do you have another transformer with an equal
number of turns? If so then you can reference the value of one against the
other using a TDR. The TDR I have been using lately has an error of + or -
1% of the total length of the cable. When you are dealing with transformers
this is very large and usually unaccpetable. Once you find the short then
what? Are you equipped to hand wind it? Good luck with you
trouble-shooting. Regards,


Jamie Gauthier
Field Service Electronics Technician
Toll Free: 800-661-0066
Fax: 780-440-2538
Cell: 780-940-3427
Pager: 780-431-7470
E-mail: jgauthier@rtdquality.com
Web Site: www.rtdquality.com


--------------------
: To the forum:

: Currently, I am testing a printed-circuit-board-mount transformer.
: There is one primary winding and three secondary windings.
: There are two powdered-iron 'E' cores that are epoxied
: together around the bobbin to provide the core for the transformer.

: I have a problem where the inductance and the Q of the primary coil
: drop way below normal past 1500 Hz with a signal of 100millivolts AC
: applied. I suspect that there is a shorted turn of wire that may be causing
: this.

: Generally, there is maybe 1000+ turns of wire on the transformer, and the
: chances of finding a marginal short-circuit with merely a microscope and
: the eyes is a 'needle-in-a-haystack' type of chance. Is there some
: method that would incorporate an electrical signal that would enable me
: to find a short-circuit in the primary winding?

: Any and all ideas are welcome. Questions are also welcome.

: Regards,

: Kelly Schauf




 


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