Shorted Secondary Winding In SMPS
For your information, i came across shorted primary winding in SMPS transformer but rarely on the secondary winding. So far i came across only few SMPS transformer that have bad secondary winding. If you come across any SMPS that produce lower output on all the output lines, don’t just suspect components fault in the primary section or even in the Optoisolator circuit- check also the primary winding. A partial short in the primary winding not necessary will cause the Main fuse and power FET to blow. Sometimes it will cause all the output to have lower voltage. You have to test the primary winding with a coil/flyback tester and the reading should light up 4 LEDs and above. If it has only one or two LEDs lights up then you know the transformer have a partial short. If it has no light at all then the primary winding have a severe short circuit.
So, first thing you must do when you come across any SMPS that produce low output, check on the primary winding before checking on other components.
(10)Dislikes
(2)
20 Comments
Leave a Reply
Waleed
October 28, 2009 at 1:28 am
thanks for the tip. it is good to know these things.
admin
October 28, 2009 at 10:26 am
Hi Waleed,
You are welcome!
Jestine
behzad
October 29, 2009 at 11:52 am
DEAR JESTIN
thank you so much of good subject but you did not tell if the transformer is open or short . where i can get one
what about new book no news from the book
rgrds
beh
admin
October 29, 2009 at 8:25 pm
Hi Behzad,
You are welcome and the transformer had a short circuit in the primary winding. As for the book, it is now going for proof reading for the second time and will let you know once it is out.
Jestine
jgmanza
October 31, 2009 at 3:55 am
Hello Jestine, so I cannot fix the crt tv as yet, because my scope has not arrived. Also I can't find who sells Blue ESR Meter as the company electronix on ebay says that they ship only to the US. So I am scratching my head when I remember Anatek Corp I saw some time ago on this site. I says "Hello Sir (John Bachman) please send me a Blue Ring Tester, a Blue ESR Meter and an Atlas component analyser because sir I really need this stuff" So he says ok, but I will send the invoice when the Component Analyser is arriving as I have to get that in stock. So I said Ok sir thank you for quick service, I read about your site on electronicrepairguide.com. So he says oh, that is right, I know Jestine he is a close personal friend.
Ha, small world.
Anyway I didn't know about that low voltage due to secondary. Thank you, that is a tip and secret.
Jorge
admin
November 1, 2009 at 8:25 pm
Hi Jorge,
No problem, in fact one has to have the ring tester in order to successfully test the primary winding of SMPS transformer.
Jestine
leonard williams
November 6, 2009 at 3:34 am
good day mr young i have mcr51r410 rca tv working on the sound is very low could tell me how to get into the service moode to ajust the sound please thanks to you .
admin
November 6, 2009 at 8:46 am
HI Leonard,
Sorry no information about this TV. In some TV, one has to press few buttons in the remote controller in order to access the service code.
Jestine
Bais Ahmad
November 6, 2009 at 10:24 am
Thanks useful info for LCD mon troubleshooting.
k.selvaraj
January 11, 2011 at 9:12 pm
very usful for yolur informaction
roshan
April 6, 2011 at 9:36 pm
engineer
i wont how switch mode transformer calculator..?
admin
April 6, 2011 at 10:27 pm
Hi Roshan,
Sorry i do not have the info.
Jestine
Mhel
May 22, 2012 at 10:30 am
Hi Mr. Yong I have here a ibm 15" lcd monitor w/ power input of 12v using adaptor and a dvi input, my problem is when ever I'm going to connect my dvi cable to pc my screen goes black and no response but sometimes it shows some image en then blank again. With only a 12v adaptor connected it working fine and shows the no cable connected message, I tried replacing the lcd panel but still the same, even with new 12v adaptor, hope you can help me with this. Thanks in advanced
Mhel
Jestine Yong
May 27, 2012 at 4:17 am
Hi Mhel,
If you connect the VGA port and it is working fine then the problem is in the DVI eeprom or even a bad MCU program. Before that make sure all the voltages from the voltage regulators ICs in the mainboard are good.
Jestine
silverthana
July 24, 2012 at 2:49 am
Hi Sir,
Can you recommeded me where I can buy the coil/flyback tester to check SMPS transformer
in Malaysia or Singapore or any Chinese brand.
Thanks
Jestine Yong
July 24, 2012 at 7:48 am
Hi Silverthana,
You can buy from me at this link http://www.electronicrepairguide.com/blue-ring-tester.html
Jestine
Mubashir
December 3, 2012 at 7:26 am
Dear Jestine, Good day
I want to ask a question regarding Switch Mode Power Supply Trasformer. is it possible that normal ATX smps Supply transformer can use in other or all smps of computers. Voltages and pin configuration is same like other smps transformer.
Thanks.
Mubashir
Jestine Yong
December 3, 2012 at 11:19 pm
Hi Mubashir,
All smps (including atx) transformers are unique and it can't be used on other equipment except on the same model.
Jestine
Tshering Tobgay
February 1, 2016 at 1:19 pm
Hi Jestine Yong sir,
i have tube samsung tv, problem with power supply, I checked 300 v dc good but there is noise from SMPS transformer,
Jestine Yong
February 2, 2016 at 8:06 am
Hi Tshering,
What was the first complaint? Have you checked if the output voltages good and stable?
Jestine