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EN 136
9.
EM5A NTSC
Parabola Generation(optional)
DAC3
+12S
7212
BC847B
11V9
SC12
11V5
7200
9V6
2
7210
BC847B
2204
3220
7206
BFS20
9V0
BFS20
15K
2206
1u
0V 7
1u
0V
SC13
1
Figure 9-30 Auto Scavem: Stage 5
Optional (depending on the set design): the Scavem signal is
modulated with a parabola. This is necessary because the
picture tube is less sensitive for Scavem in the center than on
the sides.
The 'heater' pulses on the CRT-panel are used to create a
parabola on line frequency. This parabola is made with
transistors 7204 and 7206. The DC-level of these transistors is
controlled via the DAC3 line. In this way, you can control the
parabola via software. The level is dependent on the
'sharpness meter' reading in the Auto TV program, the picture
tube size, and the sharpness setting by the customer.
Parabola Modulation and Pre-amplifier
PARABOLA MODULATION
+12S
10V9
10V9
7028
7032
BFS20
BFS20
4V2
3V5
3V5
2024
FROM
7030
BFS20
'GAIN'
1V5
0V8
PARABOLA
1
Figure 9-31 Auto Scavem: Stage 6 and 7
The Scavem signal enters at the base of transistor 7030.
Transistors 7028 and 7032 are complementary. Normally, the
same current goes through both components, but because
(7028) the parabola signal is offered on one of them, the
Scavem signal is now modulated and inverted.
After buffer 7038, the parabola signal is again added to the
(now inverted) signal, so that only the modulated signal is
available on the input of the pre-amplifier (items 7040 and
7042.)
Pre-amplification is done via a voltage amplifier (7040) and an
emitter follower (7042.)
Circuit Descriptions and Abbreviation List
PARABOLA GENERATION
11V9
3204
5V
47K
7204
BC857B
SC11
3222
BC857B
7208
7202
BC847B
6K8
CL 16532149_092.eps
PRE-AMP
11V8
7038
BFS20
SC10
10V1
SC9
2038
3102
7040
BFS20
1K5
7042
22n
BF824
PARABOLA
2
CL 16532149_093.eps
Final Amplifier (Diagram F2)
3414
3415
VD
+12V
2425
7422
SVM
A
HEAT
3450
2426
3451
+12V
201201
3452
B
2429
3455
Figure 9-32 Auto Scavem: Stage 8
Note: The figure above is taken from a previous chassis
manual, and so may deviate slightly from the EM5 execution.
However, the principle is the same.
Finally, the Auto Scavem signal arrives, via emitter follower
7422, at stage [A] on the CRT panel. Transistors 7427 and
7428, together with power transistors 7414 and 7415, form the
power amplifier, which delivers the high Scavem currents.
From the emitter of 7422, a signal is taken for stage [B]. This
signal is inverted by transistor 7425 and buffered by 7431 and
7424. The next stage is identical to that of stage [A].
At a positive alteration of the Scavem signal, transistors 7427
and 7415 in stage [A] will conduct, while 7428 and 7414 are
blocked. In stage 'B,' the positive pulse is inverted, so
SVM
transistors 7426 and 7412 will conduct, while both 7423 and
7413 are blocked. The Scavem current will now flow, via
transistor 7412, through the Scavem coil and then through
7415.
During negative alterations, the current will flow through
transistor 7414, the Scavem coil, and transistor 7413.
131201
9.18 Double Window (DW, diagram C)
9.18.1 Introduction
The Double Window (DW) panel provides the option for the
viewer to see two pictures or programs on the displayed area
of a TV screen. The displayed pictures can be in PIP mode or
DW mode. The viewer can also select the size and position of
the "second" picture.
Key components:
•
Tuner (7201.)
•
SAW Filter (1352.)
•
IF + Video processor (7301.)
•
PIP processor (7801.)
•
Switching ICs: TDA8601 (7803) and HEF4053 (7401 and
7402.)
•
IO expander (7403.)
•
V-chip (7501.)
3410
3473
3485
2420
7414
3494
7427
6414
3411
3422
3487
3488
6312
7428
2410
7415
3495
6415
3489
3413
3478
3475
3453
3474
2421
7423
7424
7431
3476
3477
7425
2424
7426
3456
3483
3484
3472
3448
2428
7412
3492
6412
3416
6317
7413
2427
3493
6413
3470
3454
CL 16532149_094.eps
201201
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