Horizontal Out - Sony WEGA KV27FV15 Training Manual

Horizontal Out

Overview
The horizontal output circuit below consists of the Horizontal Oscillator,
Horizontal Drive, Horizontal Output, Flyback and Horizontal Centering and
Linearity.
Horizontal Oscillator
When the TV is turned ON, Set +9Vdc appears and is applied to Y/C
Jungle IC355/33 and 44. IC355 contains a horizontal oscillator that is
shaped into a horizontal drive pulse that leaves at pin 19.
Horizontal Drive
Q501 amplifies this HD signal and outputs the signal from its collector.
This signal is coupled by T501 to drive the horizontal output Q502 B-E
junction.
Q502/B - 10V, 20us
Q501/B - .5V, 20us
33
Horizontal Output
Q502 is the H output transistor and it drives two circuits:
•
The deflection yoke – Develops a magnetic field in order to move the
electron beam from left to right on the screen.
•
The flyback transformers – Develops high, focus and screen voltages.
The scan derived power supplies are also developed here. They are
+200 volts, +12 volts and –15 volts for the CRT Amp and TV's vertical
section. Heater voltage for the tube's filament is also developed here.
The horizontal protection circuit also uses the heater voltage.
The HP pulse is fed back to monitor the frequency of the horizontal oscil-
lator. The horizontal output is also modulated by Q512 Pin Out. This is
necessary to correct for pincushion distortion that would be seen if cor-
rection were not used.
C510 - 10V, 20us
Horizontal Centering and Linearity
Changing the DC voltage at the return line of the horizontal yoke performs
horizontal Centering. The +135 volt line is switched through a series of
voltage dividers using S501 and S502. The different combination of switch
settings changes the DC level at the yoke return and, consequently, the
centering of the picture.
Horizontal linearity is determined by feeding back the yoke return signal
through an elaborate filter network, which is made up of T505 and its
associated components to reference of the horizontal output.
CN501/3 - 50V, 20us