Test Flyback Transformer

August 17, 2017 | Author: Anonymous ec2P0F5iKX | Category: Capacitor, Transformer, Electrical Engineering, Electrical Equipment, Electromagnetism
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Brought to you by Jestine Yong

http://www.electronicrepairguide.com

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3 Simple And Easy Steps To Test Flyback Transformer

One of the most frustrated sections in troubleshooting and repair of Computer Monitor and Television is the high voltage section. It involved the B+ circuit, flyback transformer, horizontal yoke coil, horizontal output transistor, safety capacitor and damper diode. All of the circuits and components above are easily check with just a multimeter and a digital capacitance meter but the flyback transformer was the most confusing one.

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I believe many repair technicians and engineers have problems in identifying if the flyback transformer is working or not. Assuming if the flyback was the cause of horizontal output transistor (HOT) to blow and because of lack of information, you might think the flyback is good. If this happen then you will be wasting your precious time in searching for faulty circuit that caused the HOT to blow.

A faulty flyback transformer could cause many problems in Computer Monitor and Television. Those problems are: - It causes power section to blow - Low B+ voltage - High voltage shutdown - “tic-tic” sound - Arcing sound through ground - It causes the HOT to blow either immediately or after running for couples of minutes, days or weeks later. - Blurry and bright display - No high voltage (no display) And other weird problems such as horizontal size too big and etc.

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It is very important for every electronic repairer that deals with flyback transformer to know how to test a flyback transformer.

The first step in testing a flyback transformer is: Check the internal capacitor inside the flyback transformer. If you are dealing with TV repair, then you don’t have to follow this step because usually TV flyback transformer does not have internal capacitor in it. This step only applies to Computer Monitor flyback transformer. As shown from the photo, you have to use a digital capacitance meter to measure between the anode cap and the bottom pin of flyback transformer.

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You don’t need to discharge the internal capacitor because the focus/screen divider that consists of very high ohm resistance already taken care of the charge. A good capacitance value should be around 1.5 nanofard to 3 nanofarad. However there are some Monitor designs that can go as high as 6 nano farad! Test more of them and you will be surely know what kind of value you should expect from different brand of Monitor in the future.

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Please take note that it is not 100% accurate in checking the internal capacitance with just a normal digital capacitance meter because some internal capacitor may breakdown when full load is applied. The good news is that the internal capacitor breakdown when under full load is very rare but it does happen. If you suspect the internal capacitor faulty, just direct replace with a new flyback transformer.

Second step Remove the whole flyback transformer from the mainboard and test each pin with an analog multimeter to the anode cap as shown from the picture next page. It should not have any readings and if there is a reading then the flyback transformer either had developed shorted between windings or the internal diodes had shorted. There is no way that you can repair it. The only choice is to get a new flyback transformer.

Third step First you need to find out the primary winding. By following the B+ line to flyback pin and the collector pin of HOT, that was the primary winding. A shorted winding can cause lot of problems in Computer Monitor and TV. Shorted primary winding can’t be test with a normal multimeter, it needs a special meter specially designed to test and check

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windings. The most famous flyback tester is the Dick Smith Flyback Tester. You can download the free flyback tester schematic at: http://www.flippers.com/pdfs/k7205.pdf

It can check a shorted winding even when the flyback is on board. One word of notice is that some flyback transformer primary winding only breakdown when under full operating voltage thus this meter can’t test this type of condition. Although it is not 100% in checking windings, it stills the best tester to do this job. So now you have it, go and remove the flyback transformer and start practicing it. Who knows later you can check and test any flyback transformer in less than 1 minute! If you wish to learn more about secrets of electronic troubleshooting and repair with the help of quality photos then click on the link below to find out more! http://www.TestingElectronicComponents.com I hope you’ve found this e-report useful and if you have any questions please do not hesitate to email me. Thanks! Sincerely,

Jestine Yong Founder-www.ElectronicRepairGuide.com 8

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