Filter
Top Products
1/2W, CC
470Ω
.33uF
500
1N4007
507
2,200pF
512
509
2SC3467
505
36K
511
2.2MΩ
510
2.2MΩ
514
200KΩ
503
191K
504
1.00MΩ
501
1KΩ
GND
V+
1KV
515
330pF
518
CPT1556
12
34
500V
502
0Ω
SCREEN
12-18VDC
50Vpp 29,F6
Vs
EHT
10
GND
Filament
1
332
433
453
8
7
5
4
3
2
FLYBACK
TRANSFORMER
2
1
3
4
V-
Horizontal Drive
434
1.2Ω
435
1N4007
9
NO DVM
27,G6
Hs
CPT1505
452
0Ω
V+
CPT1555
520
Dynamic Focus
465
0Ω
11
12
13
Beam Current
CRT
G1
Screen Grid.
Red Wire.
White Wire.
443
Horizontal Width Control.
(Diode Modulator)
516
270Ω
250V
0.1uF
517 1.6KV
441
GND
HORIZONTAL YOKE
Horizontal
Linearity &
Width coils.
OVP
H PLL
DM Drive
P/S Sync
#2 FOCUS
FOCUS
VERTICAL
YOKE
DEFLECTION
YC1
YC2
426
427
+
1,000uF
35V
449
385
1.2Ω, 1W
.8KVp-p
444
.01uF
.47uF
.47uF
200V
Transformer
DYNAMIC FOCUS CIRCUIT FUNCTION AND CIRCUIT DESCRIPTION.
13-15VDC
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.
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.
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.
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 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 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
515444
509
518
501449
504
500
514
501
505
507
443
518
518 517
516
453
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