Testing Flyback Transformer - How to Test and When to Replace It

Nowadays, more and more monitor comes in with flyback transformers problems. Testing flyback transformers arenot difficult if you carefully follow the instruction. In many cases, the flyback transformer can become short circuit after using not more than 2 years. This is partly due to bad design and low quality materials used during manufactures flyback transformer. The question is what kind of problems can be found in a flyback transformer and how to test and when to replace it. Here is an explanation that will help you to identify many flyback transformer problems.

There are nine common problems can be found in a flyback transformer:

a) A shorted turned in the primary winding.

b) An open or shorted internal capacitor in secondary section.

c) Flyback Transformer becomes bulged or cracked.

d) External arcing to ground.

e) Internal arcing between windings.

f) Shorted internal high voltage diode in secondary winding.

g) Breakdown in focus / screen voltage divider causing blur display.

h) Flyback Transformer breakdown at full operating voltage (breakdown when under load).

i) Short circuit between primary and secondary winding.

Testing flyback transformer will be base on (a) and (b) since problem (c) is visible while problem (d) and (e) can be detected by hearing the arcing sound generated by the flyback transformer. Problem (f) can be checked with multimeter set to the highest range measured from anode to ABL pin while (g) can be solved by adding a new monitor blur buster (For 14' & 15' monitor only.) Problem (h) can only be tested by substituting a known good similar Flyback Transformer. Different monitor have different type of flyback transformer design. Problem (i) can be checked using an ohm meter measuring between primary and secondary winding. A shorted turned or open in secondary winding is very uncommon.

What type of symptoms will appear if there is a shorted turned in primary winding?

a) No display (No high voltage).

b) Power blink.

c) B+ voltage drop.

d) Horizontal output transistor will get very hot and later become shorted.

e) Along B+ line components will spoilt. Example:- secondary diode UF5404 and B+ FET IRF630.

f) Sometimes it will cause the power section to blow.

What type of symptoms will appear if a capacitor is open or shorted in a flyback transformer?

Capacitor shorted

a. No display (No high voltage).

b. B+ voltage drop.

c. Secondary diode (UF5404) will burned or shorted.

d. Horizontal output transistor will get shorted.

e. Power blink.

f. Sometimes power section will blow, for example: Raffles 15 inch monitor.

g. Power section shut down for example: Compaq V55, Samtron 4bi monitor.

h. Sometimes the automatic brightness limiter (ABL) circuitry components will get burned.

This circuit is usually located beside the flyback transformer. For example: LG520si

Capacitor open

a. High voltage shut down.

b. Monitor will have 'tic - tic' sound. Sometimes the capacitor may measure O.K. but break down when under full operating voltage.

c. Horizontal output transistor will blow in a few hours or days after you have replaced it.

d. Sometimes it will cause intermittent "no display".

e. Distorted display i.e., the display will go in and out.

f. It will cause horizontal output transistor to become shorted and blow the power section.

How to check if a primary winding is good or bad in a Flyback Transformer?

a) By using a flyback/LOPT tester, this instrument identifies faults in primary winding by doing a 'ring' test.

b) It can test the winding even with only one shorted turned.

c) This meter is handy and easy to use.

d) Just simply connect the probe to primary winding.

e) The readout is a clear 'bar graph' display which show you if the flyback transformer primary winding is good or shorted.

f) The LOPT Tester also can be used to check the CRT YOKE coil, B+ coil and switch mode power transformer winding.

NOTE: Measuring the resistance winding of a flyback transformer, yoke coil, B+ coil and SMPS winding using a multimeter can MISLEAD a technician into believing that a shorted winding is good. This can waste his precious time and time is money.

How to diagnose if the internal capacitor is open or shorted? By using a normal analog multimeter and a digital capacitance meter. A good capacitor have the range from 1.5 nanofarad to 3 nanofarad.*

1) First set your multimeter to X10K range.

2) Place your probe to anode and cold ground.

3) You must remove the anode cap in order to get a precise reading.

4) Cold ground means the monitor chassis ground.

5) If the needle of the multimeter shows a low ohms reading, this mean the internal capacitor is shorted.

6) If the needle does not move at all, this doesn't mean that the capacitor is O.K.

7) You have to confirm this by using a digital capacitance meter which you can easily get one from local distributor.

8) If the reading from the digital capacitance meter shows 2.7nf, this mean the capacitor is within range (O.K.).

9) And if the reading showed 0.3nf, this mean the capacitor is open.

10) You have three options if the capacitor is open or shorted.

- Install a new flyback transformer or

- Send the flyback transformer for refurbishing or

- Send the monitor back to customers after spending many hours and much effort on it.

* However certain monitors may have the value of 4.5nf, 6nf and 7.2nf. Note: Sometimes the internal capacitor pin is connected to circuits (feedback) instead of ground.

Tv rca flyback transformer circuits usually do not have a internal capacitor in it.

If you have a flyback diagram and circuits which you can get it from the net, that would be an advantage to easily understand how to check them.

Jestine Yong is a electronic repairer and a writer. For more electronic repair articles please visit his website at http://www.noahtec.com/electronic-repai r-articles.htm

---

Power Protection in the Home Theater - Use of Surge Suppressors to Guard Expensive Electronic Gear

Surge Suppressors ? A First Line of DefenseAll home theater... Read More

The Printer Cartridge Game

Think you got a great deal on a printer? Like... Read More

Discover Everything About Wholesale Bar Code Reader And Software!

It is a given fact that buying wholesale would make... Read More

Ten Things Everyone Should Know about Ordering an Inkjet Cartridge Online

It is true. You can save a lot of time... Read More

LCD Vs. CRT

When buying a new computer, or upgrading your monitor, you... Read More

Protecting Your Computer From Power Surges, Data Loss, Viruses, And Spyware

Protecting Against A Power Surge:Your computer is an expensive investment;... Read More

A Technical Introduction to Audio Cables

What is so important about cables anyway?One of the most... Read More

Special Events Recording in DVD Players Age

The proliferation of portable DVD players has dramatically changed the... Read More

How To Troubleshoot DVD Drives Fast

You really enjoy those dvd movies and games and the... Read More

A Review of HP Laser Toners

Hewlett-Packard is, along with Brother and Samsung, one of the... Read More

Laptop Notebook ? Inexpensive Business Laptops

Laptop Notebook ? Your Portable OfficeIn much of today's business... Read More

Top Three Factors to Consider While Choosing a Data Center for Your Business

Data Centers are the core of the Internet. The computer... Read More

Used Laptop Computer: Your Quick Purchase Inspection Guide ? Part 2

Used laptop computers are everywhere these days. How can you... Read More

Coping with a Serious Data Loss from your Computer Hard Drive

Data loss is an expensive reality. It's a hard fact... Read More

Nvidia Geforce 7800 GTX Review

Nvidia has done it again, with it's newest video card,... Read More

How to Choose The Right Laptop Accessories?

The notebook computer is coming of age. For the first... Read More

Flash Memory Part 2: MMC and SD

MMC and SDFlash memory is available in so many formats... Read More

A Short Introduction to Blu Ray

Blu ray is a next generation optical media format developed... Read More

TiVo: An Introduction for the Few Who Dont Know Yet

TiVo will change your life... for the better. Plain and... Read More

Ergonomic Products 101

Human beings are scaling new heights day by day. Markets... Read More

Refurbished Laptop Batteries

There are three refurbished laptop battery types, each named for... Read More

How to Avoid Getting Ripped-Off When You Purchase A New Printer

It's no big secret that printer companies like HP and... Read More

Inkjet Printer Tips to Select Proper Printer

If you are tight on budget, go for Inkjet Printer.... Read More

How To Purchase A Quality Laptop Computers Case

So you finally have that new laptop you have been... Read More

Buying a Plasma or LCD TV FAQs

This article focuses on frequently asked questions by buyers of... Read More

What Is A Fuse? And How To Test It.

A fuse is a very thin wire, which either melts... Read More

The Road Ahead

We live in an area that has begun to... Read More

The Merging of Humans and Computers

Soon the human brain will be completely interfaced with the... Read More

RAM - What is It & Why You Need Plenty

This is the first article in the Understanding Your Computer... Read More

Bluetooth Can Be Cracked!

Nothing is completely safe today. Adobe has recently released a... Read More

How to Change, Upgade or Remove an IDE Hard Drive

Hard drives - Hard drives are a little more complicated.... Read More

Give Your PC a Monitor Makeover

Whether you are crunching figures at a front office job... Read More

Choosing a Tape Drive

Tape drives remain the leading technology used by organizations for... Read More