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CIRCUIT DESCRIPTION
Blanking Circuit (X74-1430-00)
Q, the output from sweep gate U2b, and the CHOP signal
obtained
by U1c and d are ANDed
at U1a to obtain the
blanking signal. After its amplitude is varied at Q17 and
Q18 by the voltage from the INTENSITY VR, it is sent to
the power-supply high-voltage unit.
X-Y Circuit (X74-1430-00)
To prevent sweeping in the X-Y mode, the sweep gate is
controlled from the mode switch via D18. The CHOP signal
oscillator is stopped via D4, the vertical mode logic is con-
trolled by D5 and D7 so that CH1 is ON and CH2 is OFF,
and the blanking signal is generated by D17. In addition,
the sawtooth wave signal is switched to the X signal from
the vertical amplifier unit, and the current signal is supplied
to the horizontal amplifier circuit.
CRT
G,
Bias
Circuit
and
ASTIG
Circuit
(X74-1430-00)
As the CRT's G, bias voltage has a large influence on its
sensitivity and intensity, it is stabilized by Q36 and output
at low impedance.
With the ASTIG circuit, +120 V is adjusted by a VR and
connected directly to the CRT's second plate.
Blanking Amplifier Circuit and High Voltage Cir-
cuit (X68-1450-00)
The high voltage used for driving the CRT is obtained using
a DC-DC converter circuit.
By the oscillation with the non-regulated
+10 V power
supply, Q3 and T1, the secondary coil of T1 outputs the
'CRT heater power and the AC power supply for the CRT
The high-voltage cathode power supply is double-voltage
rectified, high-voltage anode power supply is rectified to 6
times, and —1.5 kV and 4.5 kV high voltages are obtained
respectively. For this purpose, the converter is designed to
be a safe circuit without high-voltage leakage, having high
efficiency and low current consumption.
The converter is also made highly stable thanks to the feed-
back applied using operational amplifier U4b.
For the blanking amplifier circuit, the blanking signal from
the
horizontal
sweep
unit is supplied
to Q10
via the
emitter-follower of Q13. Q9 is the constant-voltage load of
Q10. It is subject to negative feedback so it amplifies and
outputs the signal with low output impedance.
This blanking signal is DC-regerenated by the carrier signal
from D14 to D17 and T1 to obtain a high voltage used for
driving the CRT grid No. 1.
The
focusing
high voltage
is obtained
by dividing the
cathode high voltage using a resistor with potentiometer,
and applied to the first plate.
The external intensity modulation circuit is a simplified cir-
cuit, in which the input signal is supplied via a resistor to
the
base
of Q13
of the blanking
amplifier.
The
input
voltage is +5 V, and the intensity decreases
when
the
voltage increases positively.
VR2 is the intensity adjustment control.
Power Supply Circuit (X68-1450-00)
The
constant-voltage
regulated
power
supply
circuit
is
designed to be highly stable by using operational amplifiers
U1a, U1b, U2b, U3a and U3b as the error amplifiers of all
of five lines. Q1 to Q7 are the control transistors. VR1 is
used to adjust — 10 V, which is the reference voltage of all
error amplifiers.
Calibration
Voltage
Generator
Circuit
(X68-1450-00)
This is an oscillation circuit using operational amplifier U2a
and outputs a highly stable signal. VR3 is used to adjust the
amplitude of the calibration voltage output.
Trace Rotation Circuit (X68-1450-00)
Q11 and Q12 supply current to the rotator coil.
Scale Illumination Circuit (X68-1450-00)
The power is supplied via an independent line deriving from
the +10 V coil of the power transformer. The voltage is
rectified by diode bridge D22 and supplied to the illumina-
tion lamp via a VR and control transistor Q14.
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