Flyback Transformer-How to Locate the ABL Line

Whenever there is a complaint about monitor contrast problem I will check on the flyback transformer ABL (automatic blanking limiter) circuit. Sometimes a weak picture tube might caused contrast problem. If the picture tube is good, I will go straight to the contrast circuit. The question is how do we find where the contrast circuit located? Simple, if you have a datasheet for the video pre- amplifier ic, definitely you can find the contrast pin. For LM1203N video pre-amp ic the contrast pin is located at pin 12. Replace this ic or trace from this circuit to find the cause of the contrast problem.

From experienced, usually capacitors shorted and resistor turned into high ohms were the caused of the problem. A video pre-amplifier can also be defective. To confirm whether is circuit or ic problem, just solder out the contrast pin and switch on the monitor. If the monitor display normal picture (contrast ok) then suspect the abl line circuit. If it remain the same (dim contrast) replace the video pre-amp will usually solve the problem.

The contrast signal came from one of the pin (leg) of a flyback transformer which we called it as abl pin. Many technicians have the difficulty to trace the abl pin because usually a flyback transformer consist of around 10 pins. Some pins are B+, GROUND, AFC, ABL, X-RAY PROTECT, VCC, to HOT, HEATER, horizontal centering and etc. But there is one and simple way that i'm gone to show you how to locate the abl pin. Use two analog multimeters set to x10kohm range. Connect it in series (+ probe to - probe) and measure the flyback transformer from anode (the red cap) to all of the pins under the flyback. You have to desolder all the pin or just remove the flyback from the mainboard in order to get an accurate reading.

If either one of the pin shows a diode reading that is the abl pin. The reason we use two multimeters is because the flyback circuit internally have couple of high voltage diodes connected in series. If you have a schematic diagram or any monitor or television troubleshooting book, you will see that the internal flyback diode are connected in series. By connecting two meters the ouput from the probe is around 24 VOLTS which is enough power to check the flyback internal diodes. After you have determined the abl pin, you can proceed to follow the line and find the bad components that cause the contrast problem.

Television or tv flyback transformer generally have the same design compare to monitor flyback. Whether it is a montblanc flyback transformer, rca, mitsubishi or sony flyback the checking usually is the same.

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

---

Hard Drive Selection

Perhaps the biggest mistake people make when building their computer(s)... Read More

Flash Your ATI Video Cards BIOS

Flash your ATI video card BIOS.You will need the following:1.... Read More

Whats In An LCD Display?

Who needs an LCD display? Well, if you're like me,... Read More

Facing DVD Software Dilemma? Its Brainlessly Simple

The Pocket DVD Wizard allows you to make backup copies... Read More

Tips To Select Proper Hard drive

Day by day computers are getting advanced. Capacity and performance... Read More

Wireless Notebooks: What You Need To Know About Going Wireless!

It's not exactly breaking news that our world is becoming... Read More

How to Purchase a Flat Panel TV

When purchasing a flat panel TV, there are a few... Read More

Expansion Cards Part 1: (of a 3 part series)

PCIThe expansion slots available on motherboards allow for a variety... Read More

How To Choose A Computer Case

Things to Consider When Choosing a Computer CaseIn the past,... Read More

The Top 10 Must-Have Laptop Accessories

You've laid out good money for your laptop computer, but... Read More

Getting to Know Inkjet Printers

Inkjet printers were born in the 1980s, replacing the popular... Read More

Build Your First Computer from Hardware Scratches

Wow- if you do it first time and have some... Read More

Ergonomic Products 101

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

What You Should Know Before You Buy Computer Equipment

You will have many factors to consider when deciding on... Read More

Setting up a Network -- Wired or Wireless?

To Wire or Not to Wire Wireless networks... Read More

Your Hard Drive is Going to Explode ? Why a UPS is Essential

It's most peoples worst computing nightmare. You wake up in... Read More

Testing Diode -The Accurate Way on How to Test Semiconductor Diode Using Multimeter

Testing diodes is different from testing a resistor because you... Read More

Power and Your PC

The power coming into a computer is the most critical... 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

Understanding Transistor Data and Replacement

If, for some reason, you can't get an exact replacement... Read More

What Everybody Should Know About An Inkjet Printer: The One-Year Cost Of Printing

You can purchase an inkjet printer for as little as... Read More

Lock Workstation Fast

When you work in an office, it's important to lock... Read More

Alternatives to Tape Backup

You may ask, isn't tape an anachronism in the age... Read More

Where Can I Find The Best Case Mods Online and Save Money?

Are you captivated by the stunning Case Mods you've seen... Read More

Portable MP3 Player Based Education

A revolution in learning technology has taken place. Actually, it... Read More

The Printer Cartridge Game

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

DVD Recorders: Getting Started

IMO, these sd work 'like a VCR' as far as... Read More

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

Nowadays, more and more monitor comes in with flyback transformers... Read More

DVD Media

DVD is an optical disc storage media format that can... Read More

Discover Everything About Wholesale Bar Code Reader And Software!

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

To Upgrade or Not?

To upgrade or not? That is the question. At least,... Read More

A Review of Refurbished Toshiba Laptops

Toshiba offers a few of their refurbished laptops in the... Read More

All In One Printers ? Home Office Workhorses

All in one printers, also known as multifunction printers (MFPs),... Read More