Horizontal Deflection - Beehive International B102 Service Manual

2.3 HORIZONTAL DEFLECTION
To obtain a signal appropriate for driving Q106, the horizontal output transistor,
a driver stage consisting of Q105 and T101,is used. The circuitry associated
with Q105 and Q106 has been designed to optimize the effeciency and reliaUlity
of the horizontal deflection circuits.
A positive going pulse is coupled through R127 to the base of Q105. The amplitude
and duty cycle of this waveform must be as indicated in the electrical specifi
cations (Section 1.2) for proper circuit operation.
The driver stage is either cut off or driven into saturation by the base signal.
The output signal appears as a rectangular waveform and is transformer-coupled
to the base of the horizontal output stage. The polarity of the voltage at the
secondary of the driver transformer is chosen such that Q106 is cut off when
Q105 conducts and vice versa.
During conduction of the driver transistor, energy is stored in the coupling
transformer. The voltage at the secondary is then positive and keeps Q106 cut
off. As soon as the primary current of TlOl is interrupted due to the base
signal driving Q105 into cut off, the secondary voltage changes polarity. Q106
starts conducting, and its base current flows. This gradually decreases at a
rate determined by the transformer inductance and circuit resistance.
The horizontal output stage has five main functions: to supply the yoke with
the correct horizontal scanning currents; develop a "C" VDC supply voltage
for use with the CRT; develop a "B" VDC supply voltage for the video out
put stage; and develop a "D" VDC for the CRT bias.
Q106 acts as a switch which is turned on or off by the rectangular waveform
on the base. When Q106 is turned on, the supply voltageplus the charge on
C113 causes yoke current to increase in a linear manner and moves the beam
from near the center of the screen to the right side. At this time, the
transistor is turned off by a positive voltage on its base which causes the output
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