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

---

Laptop Computer Extras for the Mobile Traveler

A laptop computer certainly provides you with an unprecedented level... Read More

War of the Disks: A Close-in Analysis of the Hard Disk Drive vs. the Solid State Disk

Much has been written about solid state disks (SSDs) becoming... Read More

10 Things to Ponder Before Moving Your Office Network

Moving the office network? How hard could it be? Anybody... Read More

Ten Tips to Safeguard Your Laptops

The following is a list of tips to help safeguard... Read More

How To Choose The Best Gaming Laptop

The gaming laptop is coming of age! It is steadily... Read More

How To Buy The Perfect Student Laptop

If you are like most student's, money isn't exactly growing... Read More

Computer Components for Idiots

There are many fancy add-ons for computers, but the basic... Read More

10 Solid Reasons To Make Your Next PC A Notebook

Notebook computers are becoming very popular. They seem to be... Read More

Cisco CCNA Certification: An Illustrated Guide To Ethernet CSMA/CD

When you're studying for your CCNA exams, you're going to... Read More

Printer Cartridge Economics -- Four Ways To Make Your Ink Last Longer

Printer cartridge overheads can be a major expense for any... Read More

Buying a Refurbished Dell Laptop

Dell offers a full line of refurbished laptops on their... Read More

What Can You Do With A Mac Mini?

If you have not seen the newest addition to the... Read More

7 Steps to Cleaning the Laser Toner From Your Laser Printer

Cleaning a laser printer, fax, or copier of laser toner... Read More

How To Upgrade Your PC

Before you upgrade your PC hardware it's best to search... Read More

The Printer Cartridge Review

Years ago computers were huge and their accompanying printers were... Read More

What Tablet PCs Can Do for You

Tablet PCs are great. If you are a mobile person,... Read More

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

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

Looking for Information on CD Duplication and Replication?

Time is one of the most important things we have... Read More

Drop On Demand Printers

Most HP and Epson printers are drop on demand printers.... Read More

How to Read CRT Tube Part Numbers

All picture tubes, whether monochrome or color type are identified... Read More

Laptop and Notebook Theft Prevention

Laptops or Notebook computers are an expensive personal and business... Read More

Sony vs. Olympus: Digital Voice Recorders

Digital voice recorders have become increasingly popular over the last... Read More

How to Purchase a Flat Panel TV

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

How To Take Care Of Your Laptop Computer

As the proud owner of a laptop computer, you'll want... Read More

LCD Monitors: A Catching-On Technology

If you've been in the market for a new computer... Read More

Your Business versus Mother Nature

Business Consultants earn hundreds of thousands of dollars every year... Read More

The Importance Of Current Sense Resistor In Switch Mode Power Supply

Current sense resistor is usually located in the switch mode... Read More

A Review of HP Laser Toners

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

Trouble-shooting Hard Drive Problems - Part 1

It is extremely important not to make or write any... Read More

Selecting a Laptop

Small Can Be BeautifulWhen purchasing a new computer, you may... Read More

Computer Parts Online

In today's age, building computers on yourself is often chosen... Read More

To Upgrade or Not?

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

Blu-ray: A Primer

Blu-ray is an optical disc format which is set to... Read More