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circuit to oscillate. A high reactive voltage in the form of a half cycle negative
voltage pulse is developed by the yoke's inductance and the primary of T2. The
peak magnetic energy which was stored in the yoke during scan time is then
transferred to C109 and the yoke's distributed capacity. During this cycle, the
beam is returned to the center of the screen.
The distributed capacity now discharges into the yoke and induces a current in a
direction opposite to the current of the previous part of the cycle. The magnetic
field thus created around the yoke moves the scanning beam to the left of the
s c r e e n .
After slightly more than half a cycle, the voltage across C109 biases the damper
diode CR103 into conduction and prevents the flyback pulse from oscillating.
The magnetic energy that was stored in the yoke from the discharge of the distributed
capacity is released to provide sweep for the first half of scan and to
charge C113 through the rectifying action of the damper diode. The beam is then
at the center of the screen. The cycle will repeat as soon as the base voltage of
Q106 becomes negative.
C113, in series with the yoke, also serves to block DC currents through the
yoke and to provide "S" shaping of the current waveform. "S" shaping compen
sates for stretching at the left and right sides of the picture tube because the cur
vature of the CRT face and the deflected beam do not describe the same arc.
LlOl is an adjustable width control placed in series with the horizontal deflection
coils. The variable inductive reactance allows a greater or lesser amount of the
deflection current to flow through the horizontal yoke and, therefore, varies the
width of the horizontal scan.
The negative flyback pulse developed during horizontal retrace time is
rectified by CR104 and filtered by CllO. This produces approximately "D"
VDC which is coupled through the brightness control to the cathode of the
CRT (VI).
A-5
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