(e) The circuits depending on this power supply require a more precise
regulation. As is the same case for most of the digital and analog sections, three terminal
regulators (VR-1, VR-2, and VR-3) are used. Also, the medium voltages and the negative
bias for the CRT have their regulation enhanced by the use of suitable zener diodes
(CR22 through CR26).
(3) Magnetic deflection circuit. With the exception of the input signal
conditioning for the sweep and one resistor value, both deflection stages are identical.
Therefore, only one stage will be described.
(a) The deflection signal amplitude can be controlled by R231 or R241.
The deflection signal is amplified by one section of U118. It, in turn, drives a
complementary stage (Q120, Q124) operating in class C. It has enough current capability
to drive the power transistors Q122 through 126 and Q123 through 127 again in the class
C push-pull configuration.
(b) A partial negative feedback network R235 through 245 and R236
through 246 ensures dc stability and good linearity even at the four crossover points per
cycle of signal. R239 through 240 dampens the inductive kicks. The current flowing
through the yoke produces a voltage drop across R232 through 242 which is the overall
negative feedback. This configuration is strictly a current amplifier with no power
consumption during a no-signal condition. Whatever power it takes is directly proportional
to the current in the yoke. Although the sweep signal or ramp is perfectly linear, it requires
some conditioning before entering the deflection circuit in order to show a linear time base
despite the flat screen and 110 degrees deflection on the CRT.
(c) Diode assemblies CR241 and CR242 in combination with R214 slow
down both ends of the ramp signal the further it deviates from the electrical center. The
weighing of the effect of each diode assembly can be adjusted by R216 for the left side of
the screen and by R217 for the right side. CR240 and R215 compensate for the flat
negative peak value of the ramp signal which allows time for the retrace. C92 blocks the
dc signal of the ramp generator, and C94 blocks the small dc values generated by the
Battery charge indicator.
(a) The state of the battery charge meter is a moving coil micro-ammeter
with an expanded scale.
(b) Only the voltage drop across the series resistor to a 10 volt zener
diode is measured. Calibration of the meter reading is accomplished by adjusting RA13.