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DIDS-402-2AM13
and resistors R 74 through R 76.
A negative reference voltage from regulator A4
flows through a specific branch of the summing network to develop an analog
voltage.
This voltage is applied to Y -axis deflection amplifier A3 in coincidence
with a 1. 3-MHz vertical sweep signal.
4-26.2 X-Deflection Amplifier and Associated Circuits
The X- axis analog voltage is applied to the input of A2 in coincidence with
a ramp voltage from transistor Ql.
This voltage (a simple sawtooth) is developed
once per character during the interval 2(CTS+l) through 2(CTS).
The purpose
of the ramp voltage is to move the monos cope scan from left to right across the
character symbol being scanned; this is accomplished as described below.
During 2CTS, a character code is clocked into the CR register and
simultaneously Ql is turned on by a blanking pulse which occurs during 3(CTS+1).
During CTS+l, the analog voltage from the X-axis summing network is amplified
by A2 and the monos cope scan is positioned on the left side of the character
symbol.
On the trailing edge of CTS+l, Q1 is cut off by the trailing edge of the
blanking pulse, and capacitor Cl begins to charge through R2.
The steadily rising
charge on Cl is coupled through R4 and appears at the input to A2 as a sawtooth
voltage.
This voltage causes the monoscope scan to move from left to right
across the monoscope character symbol.
(Simultaneously, the minor vertical
sweep 'modulate s' the Y-axis voltage, causing the scan to sweep up and down
across the character.) On the trailing edge of 2(CTS), a second character code.
is clocked into the CR register.
Simultaneously, the ramp voltage collapses due
to C1 discharging through Ql and the cycle repeats for the next character code.
A Y -skew correction voltage is developed by the resistive network formed
by resistors R16 through R20.
The purpose of R16 (X-skew) is to balance the
outputs of Q2 and Q3.
This applies an equal voltage of opposite 'polarity to each
deflection plate.
If R16 must be adjusted off-center, a skew correction voltage is
developed and coupled to the Y -deflection amplifier.
This voltage compensate s
for angular deficiencies in the Y- and X-deflection axes •.
4-26.3 Y -Deflection Amplifier and Associated Circuits
The Y-axis analog voltage (coupled from the Y-axis summing network) is
applied to the input of A3 in coincidence with the minor vertical sweep signal.
The minor vertical sweep is developed on the timing board by a countdown
circuit which divide s the master clock by a factor of two.
The 1.3-MHz square
wave signal (phase-shifted 180 degrees on alternate CRT scans) is applied to
transistor Q6, which is connected as a common emitter to the diddle coil.
The
diddle coil (which produces the CRT scan horizontal line width) is a resonant
circuit that changes the minor vertical signal to a sine wave.
This sine wave
(which occurs at a rate of 12 times per character) is applied through a phase
forming network to the input to Y-axis deflection amplifier A3.
The minor vertical sweep signal is combined with the Y-axis analog voltage
and the X-axis skew voltage and amplified by differential amplifier A3.
The
push-pull outputs of A3 are coupled to a second push-pull amplifier formed by
Q4 and Q5 to form (+) and (-) Y-axis deflection voltages.
These voltages increase
4-155
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