T heory of Operation-60a
r - - - - - - - - - - - - - - - - - - - - - ,
I
I
I
I
I
I
I
R860
C860
C R860
F ROM PIN 10
O F T850
Z-AX IS AMPL I F I E R
OUTPUT F ROM R599
(NORMA L LY F R OM
+1 0 TO +80 V)
C R T BIAS
R862
r - - - - - - ·
-
-
-
-
- - - -
-
- - - - - - - - -
-
..,
I
I
C879
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I
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I
I
CRT CONT ROL
I
- - - -
G R I D
I
I
C RT CATHODE
I
I
MODU LATOR
L
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
.J
I
R876
I
I
CATHODE SUPPL
V
(-4500 V )
DEMODU LATOR
I
L
_ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _ _
J
NOTE
A L L VOL TAG ES G IVEN ON THIS
I LLUSTRATION ARE APPROXI·
MATIONS, NOT N ECESSA R I L Y
T HOSE FOUND I N THE ACTUAL
CI RCUIT.
- - - - - - C R T CUTO F F LEVE L
.
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.
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.
•
•
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.
.
.
+1 10 V
�---
- Z-AXIS AMPL I F I E R OUTPUT LEV E L
_
_
_
_
_
_
_
.1 0 V
1 00 V
D I F F ER ENCE
.
.
.
.
.
.
.
. . .
.
-45OO V
l)
STI LL
I
DI F F ERENCE
_ _
-
_
CATHODE SUPPLY
&
AMPLITUDE O F
-4600 V
( 2025-15) 2305-9
Figure
4-4.
Simplified diagram of Control-Grid
DC
Restorer.
increase in positive voltage across C929. When the
secondary-winding output swings negative, CR925
turns off. Then, CR927 conducts and clamps the
negative excursion at C929 a diode drop below
ground. The result is a square-wave output from the
M odulator, with the output amplitude determined by
the difference between the level of the Dynamic Focus
circuit (diagram 4) and approximately ground (see
waveform 2 on Fig. 4-5). The M odulator output is
coupled through C929 to the Demodulator.
D emodulator
The Demodulator rectifies the signal from the
Modulator and references it to the potential on C934.
The potential on C934 is determined by voltage divider
R920D R92OC, and FOCUS control R844. The
negati
�
e swing of waveform 3 in Figure 4-5 is limited
by CR929 to the l evel of C934; the positive excursi on
is coupled through CR930 to C930. Quiescently, C930
will charge to about -3250 volts through R930. After
@
4-7
