Television 1 Jess Role @ UEAB2006 Television Sync Separator

Television 1 Jess RoTelevision 1 Jess Role @ UEAB2006le @ UEAB2006

Television Sync Television Sync SeparatorSeparator


What is sync separatorWhat is sync separator

Responsible in keeping the receiver Responsible in keeping the receiver sawtooth deflection oscillators in step sawtooth deflection oscillators in step with the transmitter sawtooth deflection with the transmitter sawtooth deflection oscillators.oscillators.

A composite video signal having positive A composite video signal having positive going sync pulses is obtained from the going sync pulses is obtained from the output of the video amplifier and is feed output of the video amplifier and is feed to th input of the sync separatorto th input of the sync separator


Amplitude separationAmplitude separation

Functions of sync separatorFunctions of sync separator Amplitude separation of the sync pulses from the Amplitude separation of the sync pulses from the

composite video signalcomposite video signal Amplification of the sync pulsesAmplification of the sync pulses DC restorationDC restoration Improvement of the noise immunity preventing loss Improvement of the noise immunity preventing loss

of the sync because of the noiseof the sync because of the noise waveform separation prevents horizontal and waveform separation prevents horizontal and

vertical sync pulses from interfering with one vertical sync pulses from interfering with one anotheranother


Sync separator blockSync separator block


Sync separators and Sync separators and deflection circuitsdeflection circuits


DC restorationDC restoration

Uses signal bias to set their operating pointUses signal bias to set their operating point It is necessary because composite video signal It is necessary because composite video signal

is often coupled from the video amplifier to the is often coupled from the video amplifier to the input to the sync separator through coupling input to the sync separator through coupling capacitor.capacitor.

Two important function of BiasTwo important function of Bias Restores the video component of the video signalRestores the video component of the video signal Form automatic bias that adjust itself as the signal Form automatic bias that adjust itself as the signal

strength changes so that only the sync pulse tips strength changes so that only the sync pulse tips are responsible for the sync separator conductionare responsible for the sync separator conduction


Waveform separationWaveform separation

The differentiator – RC circuit ca be made into The differentiator – RC circuit ca be made into high pass filter that is used to block the vertical high pass filter that is used to block the vertical sync pulses and pass and shape the horizontal sync pulses and pass and shape the horizontal sync pulses into trigger voltages for the sync pulses into trigger voltages for the horizontal oscillator. It is designed for short horizontal oscillator. It is designed for short time constant period time constant period

The integrator- low pass filter used to block the The integrator- low pass filter used to block the horizontal pulses pass and shape the vertical horizontal pulses pass and shape the vertical sync pulses for the use of vertical deflection sync pulses for the use of vertical deflection oscillator trigger voltage oscillator trigger voltage


High pass differentiator High pass differentiator


Low pass filter Low pass filter differentiatordifferentiator


Equalizing pulsesEqualizing pulses


Transistor Sync separatorTransistor Sync separator


The transistor noise The transistor noise canceling amplifiercanceling amplifier


Integrated circuits sync Integrated circuits sync separatorseparator



Vertical Countdown Vertical Countdown circuits Functioncircuits Function

Perfect interlace scanning this means that vertical Perfect interlace scanning this means that vertical resolution picture is improve because there can’t be resolution picture is improve because there can’t be any pairing of horizontal scanning linesany pairing of horizontal scanning lines

The vertical countdown circuit does not require vertical The vertical countdown circuit does not require vertical hold controlhold control

Changes in the vertical height and vertical linearity Changes in the vertical height and vertical linearity control settings can’t have any effect on the vertical control settings can’t have any effect on the vertical sawtooth frequency. In the receivers not using the sawtooth frequency. In the receivers not using the vertical countdown circuits. Changing this controls will vertical countdown circuits. Changing this controls will cause picture to rollcause picture to roll

This control is one of the master oscillator to generate This control is one of the master oscillator to generate boot the horizontal and vertical sawteeth.boot the horizontal and vertical sawteeth.


Master oscillator Master oscillator functionsfunctions

Video AmplificationVideo Amplification AGC processingAGC processing

Provides voltages to IF, Tuner VHF-UHFProvides voltages to IF, Tuner VHF-UHF Sync separationSync separation

Generate vertical and horizontal pulseGenerate vertical and horizontal pulse Noise centering amplifierNoise centering amplifier

Eliminate noise pulsesEliminate noise pulses Horizontal AFCHorizontal AFC

Correcting any frequency error (503.5 khz master scan Correcting any frequency error (503.5 khz master scan oscillator)oscillator)

Master scan oscillatorMaster scan oscillator Operates frequency of 32 times the color horizontal scanningOperates frequency of 32 times the color horizontal scanning


Vertical Countdown ChipsVertical Countdown Chips

Provide blanking pulseProvide blanking pulse Amplified by the buffer stageAmplified by the buffer stage

Provides horizontal drivesProvides horizontal drives Dividing the 503.5 Khz master oscillator Dividing the 503.5 Khz master oscillator

Provides the drive for the vertical Provides the drive for the vertical deflection amplifierdeflection amplifier Logic circuits divide it’s input signal 525 Logic circuits divide it’s input signal 525

producing 59.94 Hz producing 59.94 Hz


Sync separator problemsSync separator problems

Loss of vertical synchronization or picture Loss of vertical synchronization or picture rollroll

Loss of horizontal synchronization or Loss of horizontal synchronization or picture tearingpicture tearing

Loss of booth horizontal and vertical Loss of booth horizontal and vertical synchronizationsynchronization

Horizontal pulling or bendingHorizontal pulling or bending Vertical jitterVertical jitter


Loss of vertical syncLoss of vertical sync

Defective tube, transistor or integrated Defective tube, transistor or integrated circuitscircuits

An open integrator resistor An open integrator resistor Shorted integrator capacitorShorted integrator capacitor Open resistor between the sync Open resistor between the sync

separator and the vertical oscillatorseparator and the vertical oscillator A 60 Hz hum present in the sync A 60 Hz hum present in the sync

separator and the vertical oscillatorseparator and the vertical oscillator


Loss of vertical syncLoss of vertical sync


Loss of Horizontal SyncLoss of Horizontal Sync

Defective horizontal sync amplifier or Defective horizontal sync amplifier or transistortransistor

Open or leaky coupling capacitor or Open or leaky coupling capacitor or horizontal AFChorizontal AFC

Increased value or plate or collector load Increased value or plate or collector load resistorresistor


Loss of horizontal syncLoss of horizontal sync


Loss of horizontal and Loss of horizontal and vertical synchronization vertical synchronization

Defective transistor in the sync or noise Defective transistor in the sync or noise limiter stageslimiter stages

Video coupling capacitor open, shorted Video coupling capacitor open, shorted or leakyor leaky

Video sync isolation resistor is open or Video sync isolation resistor is open or increased in valueincreased in value


Loss of booth horizontal Loss of booth horizontal and verticaland vertical


Horizontal Bending and Horizontal Bending and pullingpulling

The video strip (video IF, tuner and video The video strip (video IF, tuner and video amplifier)amplifier)

AGC circuitAGC circuit The sync separator stageThe sync separator stage The horizontal AFC circuitThe horizontal AFC circuit The low voltage power supply filterThe low voltage power supply filter


Horizontal pullingHorizontal pulling


Possible problem are Possible problem are caused by the following caused by the following componentscomponents

Defective transistor or ICDefective transistor or IC Leaky coupling capacitorLeaky coupling capacitor Open capacitor in compensating networkOpen capacitor in compensating network Decreased plate or collector load Decreased plate or collector load

resistanceresistance Defective filtering of power supplyDefective filtering of power supply


Possible cause of vertical Possible cause of vertical jitteringjittering

Defective transistor in sync separator Defective transistor in sync separator stagestage

Defective component in the vertical Defective component in the vertical integrator network integrator network

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Television 1 Jess Role @ UEAB2006 Television Sync Separator