Circuit Description—Type 422 AC-DC
Horizontal deflection
signal to horizontal
deflection plates
Fig. 3-9. Horizontal Amplifier detailed block diagram.
zontal deflection signal is an external signal applied to the
HORIZ IN connector. In addition, this circuit contains the
horizontal magnifier circuit and the horizontal positioning
network. Fig. 3-9 shows a detailed block diagram of the
Horizontal Amplifier circuit. A schematic of this circuit is
shown on diagram 8 at the back of this manual.
Feedback Amplifier
The input sigr or the Horizontal Amplifier circuit is
selected by the TIME/DIV switch SW440. In all positions
of the TIME/DIV switch except EXT HORIZ, the sawtooth
from the Sweep Generator circuit is connected to the base
of Q513 through C511-R511 and R512. C511 provides
high-frequency compensation to improve sweep linearity at
fast sweep rates. Sweep Cal adjustment R512 is part of a
current divider which determines the sawtooth current
applied to the base of Q513. R512 is adjusted to provide
calibrated horizontal sweep rates.
Horizontal POSITION control R530A and R530B sets
the quiescent DC output level at the emitter of Q543 to
determine the horizontal position of the CRT display. This
control is a dual-range control to provide a combination of
coarse and fine adjustment in a single control. When the
control is rotated, fine control R530A provides positioning
for a range of about 0.5 division for normal sweep or five
divisions for magnified operation. Then after the fine range
is exceeded, the coarse control R530B provides rapid posi
tioning of the trace.
For EXT HORIZ operation, an external signal connected
to the HORIZ IN (TRIG IN) connector is applied to the
base of Q513 through R501, R355B and R510-R512. The
HORIZ ATTEN control R355B (TRIGGERING LEVEL)
provides about 10:1 variable attenuation for the external
horizontal signal. For external horizontal operation, the
Sweep Generator circuit is disabled so there is no sawtooth
input. The TIME/DIV switch connects a positioning voltage
to the base of Q513 through R516 and R515 in the EXT
HORIZ position. This voltage positions the external hori
zontal display near the center of the display area horizon
tally when the horizontal POSITION control is centered.
Transistors Q513, Q524 and Q543 are connected as a
feedback amplifier with capacitive feedback from the col
lector of Q524 and resistive feedback from the emitter of
Q543. Diode D512 in the base circuit of Q513 limits the
positive signal change at the base of Q513 to about +0.6
volt. Diode D513 protects Q513 from reverse-voltage
damage and D524 prevents Q543 from going into satura
tion when overdriven (X10 magnification). For X I magnifi
cation (X10 MAG switch pushed in) the resistive feedback
through the parallel paths of R537 and R527 sets the gain
of the stage so the horizontal deflection on the CRT is
calibrated (with correct adjustment of Sweep Cal R512).
The bias network R535-R536 determines the center-screen
DC level at the emitter of Q543. Mag Register adjustment
R535 in this network is set so tms center-screen voltage is
the same for XI magnification as for X I0 magnification
3-16
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