Model 141A Section IV
Paragraphs 4-22 to 4-31
t RECTI F I ER
e DOUBLER
V602, V603
HIGH VOLTAGE
TRANSFORMER II
(
T601
(--'
-RECTIFIER
IC,
V604 <--I
OSCILLATOR ,.---
0602 1
id
-RECTIFIER
11
V605
REGULATOR
V601,0601
HIGH
1, YI1- 8-3
Figure 4-3. High-Voltage Power Supply Block Diagram
of the CRT. The negative output voltages are used post-accelerator, and phosphor screen. In addition,
in the gun assembly of the CRT and its associated there are two flood guns (filaments, cathodes, and
controls. The Z-axis input can be used to apply in- grids only), a collimator, a collector mesh, -and a
tensity modulating signals to the CRT. storage mesh. These added elements make possible
the variable persistence and storage functions of the
4-22. Figure 5-8 is a schematic diagram of the high-
Model 141A.
voltage supply and the CRT. Oscillator Q602 operates
at a frequency of approximately 32 kHz. Any change 4-28. FLOOD GUNS. The flood guns are physcially
in the output voltage is applied to the grid of V601, located on the electron gun outside of the horizontal
which converts the voltage change toa current change. deflection plates. Horizontal Drivers, Q603, and
This current change is applied, by Emitter Follower Q604 prevent flood gun electrons from flowing through
Q601,to the base of the oscillator transistor. The the deflection plates to the output stage of theplug-in.
amplitude of oscillations is changed in such a direc- The gun operates continuously when the power switch
tion as to oppose the original output voltage change. is on. An electron cloud, which is emittedbytheflood
High-Voltage Adjust R619 sets the amplitude of oscil- guns, is accelerated toward the CRTscreenby colli-
lation to produce the correct output voltage. mator and collector mesh voltages. These electrons
make stored or persisting displays visible
4-23. Two separate negative supplies are used, one
also used to erase stored and persisting dis
for the control grid of the CRT, and one to provide
CRT cathode and focusing voltages. Both supplies 4-29. COLLIMATOR. The collimator is
use half wave rectifiers (V604 and V605). The un- coating along the tapered portion of the CR
blanking gate from the horizontal plug-in (pin 1, 52) tive voltage applied to the collimator focus
is applied to the return side of the grid supply, and gun electrons. The cloudelectrons are fo
changes the negative grid voltage by about +50 volts column perpendicular to, and approximately
to unblank the trace. A positive pulse of about 20 the diameter of, the CRT screen.
volts will blank the trace when applied to Z-axis in-
4-30. COLLECTOR MESH. The collecto
put. When Z-axis input is not used, S601 is set to
between the flood guns and the storage mesh (closest
MT to receive chopped blanking from a dual-trace
to the storage mesh). It is always positive with re-
plug-in.
spect to the storage mesh except in the ERASEposition
4-24. The voltage doubler circuit provides the 5-kv of the PresentationSelector; bothare then at the same
post-accelerating voltage applied to the CRT. potential. In addition to accelerating flood gun elec-
trons, the collector mesh also repels positive ions
4-25. The ASTIGMATISM adjustment, R461, affects
generated by the flood guns.
the roundness of the spot, and the Geometry adjust-
ment, R643, is used to optimize pattern shape. 4-31. STORAGE MESH. The storage mesh is just
behindthe CRT screen and is coated withnon-conducting
4-26. STORAGE CRT.
material. It is statically held at a slightly positive
4-27. Refer to Figure 5-8 for the schematic diagram potential(approximate1y +3 volts). When the electron
of the storage CRT, V610. The CRT contains the con- beam from the writing gun strikes the mesh coating,
ventional electron (writing) gun, deflection plates, secondary electrons are emitted. This secondary
02567-1 4-3 |
ACEC
