Comments on: Testing SMPS Transformer Without Load

By: John Patrick

John Patrick — Tue, 24 Sep 2024 02:04:26 +0000

Hi, Can you help me how to measure the output power of smps transformer including the test setup, test equipment and schematic diagram?
Also, can you give me an Idea how can I overload SMPS Transformer.

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By: Peter gay

Peter gay — Sun, 30 Jan 2022 00:29:21 +0000

Dear Sir I built a 700 watt Smps designed by Long Technical it supposed to get 7amp with 50-0-50 volts I get the voltage but I cannot get the Amps Max3.3 amps The original trans was ER42 I changed it to ETD49 (Cause I could not fit all the wires in the ER42) If try to get more than3.3amps the fets blow up, Could you help. Thx.

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By: Efijemueh Philip

Efijemueh Philip — Fri, 13 Aug 2021 19:10:24 +0000

Hi sir,l am new to electronic and am working on a crt TV that has standby red light on but it won't turn on whether with remote or pressings the button at the front. The smps transformer output at the diode are B+98v,35v,5.5v and 8v instead of b+126v,35v,6.5v and 14v.please does it mean that the transformer is bad.thanks

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By: Arnel balbido

Arnel balbido — Fri, 21 Dec 2018 00:14:33 +0000

In reply to Mohit.

Sir what happen to the circuit specially in CRT TV if the primary of smps transformer is open winding ?

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By: Jestine Yong

Jestine Yong — Tue, 13 Nov 2018 08:55:25 +0000

In reply to sadegh.

Hi Sadegh,

The resistance method is to check if the DC output rail have any shorted components or not. Sometimes a shorted load can cause the DC outout rail to have low resistance.

Jestine

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By: sadegh

sadegh — Sun, 11 Nov 2018 17:54:52 +0000

hi sir
can i ask you something?
i read your SMPS book and it is awesome
but i do not understand resistance testing method
i read your translated book
it may translator does not good.
any way can you explain more to me??

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By: Jestine Yong

Jestine Yong — Tue, 16 Oct 2018 01:20:26 +0000

In reply to Christina.

Hi Christina,

There are many websites explaining how SMPS works. Below is just one of the websites:

https://www.efxkits.us/switch-mode-power-supply-smps-works/

Jestine

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By: Christina

Christina — Mon, 15 Oct 2018 16:38:58 +0000

In reply to Jestine Yong.

Thank You sir..One more question..The electrolytic capacitor gives dc output.Then it is given Mosfet..How the transformer gets ac input?Does the mosfet switches it to ac?..Can you explain in detail about that and the how the process goes further in remaining components(schottky diode,optocoupler) after switching?

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By: Jestine Yong

Jestine Yong — Tue, 09 Oct 2018 00:39:04 +0000

In reply to Christina.

Hi Christina,

The input should be AC and not DC. Many factors can cause no output voltage such bad fuse, bad power IC, shorted secondary output diode, open start up resistor and etc. Auxiliary winding is the secondary winding in primary side. You can't test the primary winding using multimeter. You need a blue ring tester. I suggest that you get my ebook http://powersupplyrepairguide.com/ to understand about the safety, function of each SMPS circuit and how to troubleshoot and repair.

Jestine

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By: Christina

Christina — Fri, 05 Oct 2018 16:04:50 +0000

hi Sir ,

I have an smps to repair..When I tested with multimeter I can get the dc around 220 on the input of the smps transformer..But I didn't get any reduced output.I am also confused about the auxillary winding..Can You please explain?Also tell how to test the transformer by multimeter.

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