Genius 2793 User Manual
1/2W, CC
470
Ω
.33uF
500
1N4007
507
2,200pF
512
509
2SC3467
505
36K
511
2.2M
Ω
510
2.2M
Ω
514
200K
Ω
503
191K
504
1.00M
Ω
501
1K
Ω
GND
V+
1KV
515
330pF
518
CPT1556
1
2
3
4
500V
502
0
Ω
SCREEN
12-18V
DC
50Vpp 29,F6
Vs
EHT
10
GND
Filament
1
332
433
453
8
7
5
4
3
2
2
FLYBACK
TRANSFORMER
2
1
3
4
4
V-
Horizontal Drive
434
1.2
Ω
435
1N4007
9
NO DVM
27,G6
Hs
CPT1505
452
0
Ω
V+
CPT1555
520
Dynamic Focus
465
0
Ω
11
12
13
Beam Current
CRT
G1
Screen Grid.
Red Wire.
White Wire.
443
Horizontal Width Control.
(Diode Modulator)
516
270
Ω
250V
0.1uF
517
1.6KV
441
441
GND
HORIZONTAL YOKE
Horizontal
Linearity &
Width coils.
Linearity &
Width coils.
OVP
H PLL
DM Drive
DM Drive
P/S Sync
#2 FOCUS
FOCUS
VERTICAL
YOKE
DEFLECTION
YC1
YC2
426
427
+
1,000uF
35V
35V
449
385
1.2
Ω
, 1W
.8KVp-p
444
.01uF
.47uF
.47uF
200V
Transformer
DYNAMIC FOCUS CIRCUIT FUNCTION AND CIRCUIT DESCRIPTION.
13-15
VDC
3-5Vpp 31,F5
Vs
0VDC
1.6Vpp
Vs
Vs
Vs
Hs
Model 1793-31.5DF
The dual focus CRTs require a waveform on the #2 focus grid. This voltage waveform is dependent on the
position of the beam on the CRT. The lowest voltage part of the waveform is in the center of the screen and the
highest voltage part of the waveform is at the corners of the screen.
position of the beam on the CRT. The lowest voltage part of the waveform is in the center of the screen and the
highest voltage part of the waveform is at the corners of the screen.
The dynamic focus circuit produces a composite waveform which consists of the horizontal parabolic waveform
and the vertical parabolic waveform. This composite waveform is applied to the dynamic focus input, of the
flyback transformer, and produces a sharp picture on the dual focus picture tubes. Typically dual focus picture
tubes produces a sharper picture than the single focus picture tubes.
and the vertical parabolic waveform. This composite waveform is applied to the dynamic focus input, of the
flyback transformer, and produces a sharp picture on the dual focus picture tubes. Typically dual focus picture
tubes produces a sharper picture than the single focus picture tubes.
Dynamic Focus Circuit Operation: The vertical component of the dynamic focus circuit is derived by
amplifying the voltage waveform across the vertical yoke coupling capacitor. The horizontal component of the
dynamic to focus circuit is produced by applying the voltage waveform across the horizontal yoke coupling
capacitor to the dynamic focus transformer primary. This transformer steps up the horizontal parabolic
voltage from about 33V to about 300V to produce the horizontal component of the dynamic focus circuit.
amplifying the voltage waveform across the vertical yoke coupling capacitor. The horizontal component of the
dynamic to focus circuit is produced by applying the voltage waveform across the horizontal yoke coupling
capacitor to the dynamic focus transformer primary. This transformer steps up the horizontal parabolic
voltage from about 33V to about 300V to produce the horizontal component of the dynamic focus circuit.
Circuit Description: Transistor
509
amplifies the vertical parabolic waveform which exists across capacitor
449
. This waveform is coupled to the transistor base via capacitor
500
and resister
501
. The bias for this
transistor is generated by resistors
503
and
504
. The gain of this amplifier is defined by resister and
505
.
Note; Resister
505
is connected to the vertical feed back line and not to ground. The supply voltage for the
collector is produced by diode
512
which rectifiers the primary flyback pulse and is integrated by capacitor
507
.
The load resisters for this transistor are resistors
510
and
511
. The waveform on the collector, which is the
vertical parabolic waveform, is conducted through resister
514
and through transformer
518
to the dynamic
focus input of the flyback transformer. Resisters
514
and
501
provides arc protection for transistor
509
. The
horizontal component of the dynamic focus waveform is produced by coupling the primary of the dynamic focus
transformer at
transformer at
518
to the horizontal yoke coupling capacitors at
443
and
444
. Capacitor
515
provides a low
impedance pass to ground for the horizontal parabolic waveform which is developed across the dynamic focus
transformer secondary at
transformer secondary at
518
. Capacitor
517
insures that there is no D. C. component across the
transformer primary. Resister
516
protects the dynamic focus transformer primary from overload.
The flyback transformer
453
couples the dynamic focus waveform to the #2 focus grid via an internal capacitor.
509
503
505
512
510
511
514
515
444
509
518
501
449
504
500
514
501
505
507
443
518
518
517
516
453
86