Vertical Deflection - Sony WEGA KV27FV15 Training Manual

Vertical Deflection

The vertical deflection stage consists of the Vertical oscillator, Vertical
amplifier, Flyback generator and the Deflection yoke.
The purpose of this stage is to manufacture a magnetic field. The
magnetic field will bring the electron beam gradually from top to bottom
(vertically) and then quickly back to the top (beam retrace) of the screen
to start over again.
Vertical Oscillator
When the TV is turned ON, Set +9Vdc appears at Y/C Jungle IC301/33
and 44. The internal horizontal oscillator begins and is counted down
(divided) to 60 Hz to become the vertical drive signal.
The drive signal is formed into a positive and negative ramp and its
amplitude and linearity are determined by the serial data from IC001
Tuning Micon. If the data or clock signal at IC355/34 and 35 were
missing, there would be NO vertical drive at IC301/13 and 14.
Vertical Amplifier
IC561 Vertical Output is a single package vertical amplifier that outputs
a waveform with sufficient amplitude and current to drive the deflection
yoke. It is powered by +12 and –15 volts from the flyback transformer
secondary.
Flyback / Boost Generator
The vertical boost signal is used to generate extra current in the deflec-
tion yoke during the retrace period. This extra current is used to quickly
return the electron beam to the top of the picture.
The flyback generator stage within IC561 uses the vertical signal to
make a 30Vp-p pulse needed during retrace time. The retrace portion
of the vertical drive signal input IC561/1 and 7 is extracted and ampli-
fied, and appears at pin 3 as a 30Vp-p pulse. It passes through C565
to provide sufficient current to power IC561/6 during retrace time.
Diode D561 blocks this pulse from the +12 volt source.
The vertical flyback pulse from IC561/3 is sent to the WA board to be
used by the Quadra Pole Focus circuit. It is also goes to C564. C654
blocks any DC and allows the flyback pulses to be applied to Q652/B.
27
These pulses keep Q652 ON and prevents C563 from charging. There-
fore Q561 is always OFF while the set is operating normally. If the verti-
cal flyback pulses were missing, the voltage from the 12-volt line through
R570 would forward bias Q561 B-E. This would apply a low to IC355/15
VM Out/V Protect. If IC355/15 were to receive a LOW, the IC would blank
the video. If there were problems in this area when the unit is initially
turned ON, the result would be similar to an AKB problem. The degauss
relay would not turn OFF and the Timer LED would be flashing.
Deflection yoke
The deflection yoke translates the electrical current flowing through its
coils into a magnetic field that positions the election beam vertically.
Current flowing through the deflection yoke coil is returned to ground
through R578, R563 and R559 and TH501, which are in series. The
thermistor is used for temperature compensation. As the vertical yoke
draws more current, the resistance of TH501 lowers, allowing more
current to flow to the yokes. The voltage developed across these
resistors is fed back to the inverting input of IC561/1 through R566 to
improve linearity.
IC355/13 - 1V, 5ms
IC561/5 - 20V, 5ms
Q562/B - .5V, 5ms
IC355/14 - 1V, 5ms
IC561/3 - 20V, 5ms
CN501/5 - 1V, 5ms