Ceronix 1493 Service Manual page 64

Remote Control Board
Vertical
500Ω
Size
482
750Ω
Vertical
Raster
1K
Position
483
RC3
+12V SUPPLY
VERTICAL SYNC
The vertical sync comes from the
synchronized vertical sync interface
circuit for monitors without interlace.
For monitors with interlace the vertical
sync comes from the sync comparator
via a coupling capacitor and bypasses
the synchronizing circuit. Pin 19 of the
LA7851 is the vertical sync input and will
start the next oscillator cycle on either the
positive or negative sync pulse. The vertical
oscillator capacitor
410 410
on the leading edge of the vertical sync by the
action of an internal transistor and resistor.
Capacitor is then charged by resistor
410
410
until the next sync pulse or to
362 362
8 volts, which ever comes first. The V. osc.
frequency is set low such that the adjustment
resistor can be used to act as a vertical
363
363
hold adjustment. Solder connection
used to make this adjustment.
The vertical oscillator triggers the vertical
oscillator one shot, which outputs a pulse to
trigger the vertical sync input, pin 2, of the
LA7838. This one shot is also used to
synchronize the CRT auto bias IC.
Resistor & capacitor
361 361
timeout which must be longer than the CRT
auto bias Vs delay and shorter than the
vertical blanking. Resistors
supply the pullup for this one shot.
80
VERTICAL DEFLECTION CIRCUIT DESCRIPTION.
LA7838
HEAT
SINK
Deflection
378
+12V
1
510Ω
RC8
004
0Ω
RC6
203
486
1,000pF
369
RC4
18Ω
367
Vs
discharges to 4 volts
is
V
V
set the
414
414
&
370 370 408 408
Ramp
Ramp
Reset
Vertical
One Shot
Reset
out
377
Tr.
R/C
2 3
5.5-6.4V Vs
3Vpp 21,D5
375
.01uF
44.2K
402
374
See
Table
403
V.+12V
GND
100uF
+
376
5.5-6.5V Vs
1.2Vpp 19,D5
1N4005
or
382
20 19
H.+12V
VERTICAL
VERTICAL
V+
± SYNC INPUT
The one shot in the LA7838 clamps the ramp
forming capacitor
the vertical retrace time. Capacitor
resistor
402 402
reset one shot.
The ramp capacitor
from a current generator with a 6 volt input node
at pin 4. The vertical size is adjusted by the
vertical size control
4 via resistors
range is set by resistor
deflection is set by resistor
to pin 4 comes from the vertical linearity circuit.
This circuit uses the above and below GND parts of
the vertical current waveform separately.
Transistor
waveform is below GND. This transistor's emitter
is referenced to GND by diode
. The emitter is connected to the vertical
371 371
current waveform through resistor
adjusted for each tube and yoke combination.
out
Vert.
Gen.
Drive
V. size
Control
Ramp
Slope 50/60Hz
4 5 6 7
5-6VDC Vs
5.5-6.5V
1.4Vpp 22,E5
1.4Vpp 23,F4
68.1K
393
1uF
401
GND
1.2Ω, 1W
388
385
2.2M
365K
CPC1058
362 363
.1uF
410
4-6VDC
V
2.8Vpp 18,D5
VERT.
V. osc.
OSC.
ADJ.
18
VERTICAL
OSCILLATOR
to 5 volts for about half of
401
401
form the RC circuit for the ramp
is charged by current
401 401
which is connected to pin
482 482
& . The adjustment
003 003 375 375
and the maximum
375
375
.
403 403
conducts when the vertical current
411 411
406
406
Retrace
Booster
Drive
+27V
8 9 10
Vs
470uF
380
390
392
+
391
127K
.01uF
361 414
.1-.3VCD Vs
Vs
3.8Vpp 17,E5
17
VERTICAL
OSC. O/S
and
384 374
A third input
and resistor
which is
407
407