Download Television Sync Separator

Television Sync
Separator
Television 1 Jess
Role @ UEAB2006
What is sync separator
 Responsible in keeping the receiver
sawtooth deflection oscillators in step
with the transmitter sawtooth deflection
oscillators.
 A composite video signal having positive
going sync pulses is obtained from the
output of the video amplifier and is feed
to th input of the sync separator
Television 1 Jess
Role @ UEAB2006
Amplitude separation
 Functions of sync separator
 Amplitude separation of the sync pulses from the
composite video signal
 Amplification of the sync pulses
 DC restoration
 Improvement of the noise immunity preventing loss
of the sync because of the noise
 waveform separation prevents horizontal and
vertical sync pulses from interfering with one
another
Television 1 Jess
Role @ UEAB2006
Sync separator block
Television 1 Jess
Role @ UEAB2006
Sync separators and
deflection circuits
Television 1 Jess
Role @ UEAB2006
DC restoration
 Uses signal bias to set their operating point
 It is necessary because composite video signal
is often coupled from the video amplifier to the
input to the sync separator through coupling
capacitor.
 Two important function of Bias
 Restores the video component of the video signal
 Form automatic bias that adjust itself as the signal
strength changes so that only the sync pulse tips
are responsible for the sync separator conduction
Television 1 Jess
Role @ UEAB2006
Waveform separation
 The differentiator – RC circuit ca be made into
high pass filter that is used to block the vertical
sync pulses and pass and shape the horizontal
sync pulses into trigger voltages for the
horizontal oscillator. It is designed for short
time constant period
 The integrator- low pass filter used to block the
horizontal pulses pass and shape the vertical
sync pulses for the use of vertical deflection
oscillator trigger voltage
Television 1 Jess
Role @ UEAB2006
High pass differentiator
Television 1 Jess
Role @ UEAB2006
Low pass filter
differentiator
Television 1 Jess
Role @ UEAB2006
Equalizing pulses
Television 1 Jess
Role @ UEAB2006
Transistor Sync separator
Television 1 Jess
Role @ UEAB2006
The transistor noise
canceling amplifier
Television 1 Jess
Role @ UEAB2006
Integrated circuits sync
separator
Television 1 Jess
Role @ UEAB2006
Television 1 Jess
Role @ UEAB2006
Vertical Countdown
circuits Function
 Perfect interlace scanning this means that vertical
resolution picture is improve because there can’t be
any pairing of horizontal scanning lines
 The vertical countdown circuit does not require vertical
hold control
 Changes in the vertical height and vertical linearity
control settings can’t have any effect on the vertical
sawtooth frequency. In the receivers not using the
vertical countdown circuits. Changing this controls will
cause picture to roll
 This control is one of the master oscillator to generate
boot the horizontal and vertical sawteeth.
Television 1 Jess
Role @ UEAB2006
Master oscillator
functions
 Video Amplification
 AGC processing
 Provides voltages to IF, Tuner VHF-UHF
 Sync separation
 Generate vertical and horizontal pulse
 Noise centering amplifier
 Eliminate noise pulses
 Horizontal AFC
 Correcting any frequency error (503.5 khz master scan
oscillator)
 Master scan oscillator
 Operates frequency of 32 times the color horizontal scanning
Television 1 Jess
Role @ UEAB2006
Vertical Countdown Chips
 Provide blanking pulse
 Amplified by the buffer stage
 Provides horizontal drives
 Dividing the 503.5 Khz master oscillator
 Provides the drive for the vertical
deflection amplifier
 Logic circuits divide it’s input signal 525
producing 59.94 Hz
Television 1 Jess
Role @ UEAB2006
Sync separator problems
 Loss of vertical synchronization or picture
roll
 Loss of horizontal synchronization or
picture tearing
 Loss of booth horizontal and vertical
synchronization
 Horizontal pulling or bending
 Vertical jitter
Television 1 Jess
Role @ UEAB2006
Loss of vertical sync
 Defective tube, transistor or integrated
circuits
 An open integrator resistor
 Shorted integrator capacitor
 Open resistor between the sync
separator and the vertical oscillator
 A 60 Hz hum present in the sync
separator and the vertical oscillator
Television 1 Jess
Role @ UEAB2006
Loss of vertical sync
Television 1 Jess
Role @ UEAB2006
Loss of Horizontal Sync
 Defective horizontal sync amplifier or
transistor
 Open or leaky coupling capacitor or
horizontal AFC
 Increased value or plate or collector load
resistor
Television 1 Jess
Role @ UEAB2006
Loss of horizontal sync
Television 1 Jess
Role @ UEAB2006
Loss of horizontal and
vertical synchronization
 Defective transistor in the sync or noise
limiter stages
 Video coupling capacitor open, shorted or
leaky
 Video sync isolation resistor is open or
increased in value
Television 1 Jess
Role @ UEAB2006
Loss of booth horizontal
and vertical
Television 1 Jess
Role @ UEAB2006
Horizontal Bending and
pulling
 The video strip (video IF, tuner and video
amplifier)
 AGC circuit
 The sync separator stage
 The horizontal AFC circuit
 The low voltage power supply filter
Television 1 Jess
Role @ UEAB2006
Horizontal pulling
Television 1 Jess
Role @ UEAB2006
Possible problem are caused
by the following components




Defective transistor or IC
Leaky coupling capacitor
Open capacitor in compensating network
Decreased plate or collector load
resistance
 Defective filtering of power supply
Television 1 Jess
Role @ UEAB2006
Possible cause of vertical
jittering
 Defective transistor in sync separator
stage
 Defective component in the vertical
integrator network
Television 1 Jess
Role @ UEAB2006