Whenever there is a complaint about the monitor

Contrast problem I’ll check on the flyback

transform ABL (auto suppression limiter)

circuit.

Sometimes a weak picture tube can cause

contrast problem If the picture tube is

well I go straight to the contrast

circuit. The question is how do we find

where is the contrast circuit? Simple,

if you have a datasheet for the video pre-

amplify ic, you can definitely find the

contrast pine. For LM1203N video preamplifier

ic contrast pin is located on pin 12.

Replace this icon or trace from this circuit

to find the cause of the contrast problem.

From experience, usually shorted capacitors

and the resistance turned into high ohms were the

caused of the problem. A video preamplifier

it can also be faulty. To confirm if it is

circuit or ic problem, just solder the

contrast plug and turn on the monitor. Yew

the monitor shows a normal image (contrast ok)

then suspect the circuit of the abl line. if it remains

the same (dim contrast) replaces the video

the preamp will usually solve the problem.

Contrast signal cam of one of the pins

(leg) of a flyback transformer that we call

as pin abl. Many technicians have

difficulty tracing the abl pin because

Usually a flyback transformer consists of about

10 pin Some pins are B+, GND, AFC, ABL,

X-RAY PROTECTION, VCC, to HOT, HEATER, horizontal

centered and etc. But there is one and simple

way i’m going to show you how to locate the

pine abl. Use two analog multimeters set to x10kohm

tidy. Connect it in series (+ probe to – probe)

and measure the anode flyback transformer

(the red cap) to all the pins below the

fly back. You have to desolder the whole pin or

just remove the flyback from the motherboard in

to get an accurate reading.

If either pin shows a diode

reading what the pin abl is. The reason why we use

two multimeters is because the flyback circuit

internally it has a pair of high voltage diodes

connected in series. If you have a scheme

diagram or any monitor or television

troubleshooting book, you will see that the

internal flyback diode are connected in series.

Connecting two meters the output of the probe

is around 24 VOLTS, which is enough power to check

internal flyback diodes. after you have

determined the abl pin, you can proceed to follow

the line and find the faulty components that cause

the contrast problem.

Flyback transformer for television or tv in general

they have the same design compared to the flyback monitor.

Whether it’s a Montblanc flyback transformer,

rca, mitsubishi or sony flyback checking

is usually the same.