Circuit Descriptions and Abbreviation List
EN 137EM5A P/M 9.
9.17.2 Normal Scavem
Figure 9-31 Normal Scavem
With normal Scavem (as used in the EM3E), the RGB signals
are added together and differentiated before they drive the
Scavem coil. The coring block prevents that Scavem
processing is done on low signal levels.
9.17.3 Auto Scavem (Diagram SC)
Figure 9-32 Auto Scavem
This new Auto Scavem circuit includes some extra blocks:
• Clipper
• Parabola modulation
Auto Scavem is fully software controlled, by means of I
2
C. The
speed, at which Auto Scavem is adapted, is controlled by the
Auto TV algorithm. This adaptation takes place together with
the FBX initialisation, and takes about 1 second. The different
circuit stages are controlled via a DAC (item 7500, TDA8444).
The new Auto Scavem circuitry also produces higher Scavem
currents, which results in sharper pictures. For the circuit
description, the circuit is split in eight stages.
Matrix and Differentiator
Figure 9-33 Auto Scavem: Stage 1 and 2
The 2fH RGB signals are added on the SSB (see diagram B4),
and presented to the emitter of transistor 7006.
The next circuit is the differentiator. The combined signal
enters this circuit at the base of transistor 7008. The DC-level
of this transistor is controlled by the DAC7 line, which is
dependent of the “sharpness meter” reading in the Auto TV
algorithm. By means of this control signal, the voltage and
capacity of varicap diode 6000 is altered, which will adapt the
differentiator.
The slope of the differentiator is controlled by this DC-level.
The differentiation itself is done by varicap diode 6000. Output
signal goes from the collector of transistor 7010 via emitter
follower (= buffer) 7012, to the next stage.
Coring/Clipping and Gain
Figure 9-34 Auto Scavem: Stage 3 and 4
The coring circuit (items 7014 and 7016) prevent Auto Scavem
on the lowest signal levels (= noise), while the clipper circuit
(items 7018 and 7020) always give the same amount of
Scavem above a certain level.
The levels at which this must happen, are controlled by the
DAC4 and DAC5 lines, and are dependent of the “noise meter”
reading in the Auto TV program.
The input signal enters this circuit at emitter follower 7022, and
is strongly attenuated via voltage divider R3062 and R3064.
This, because the gain of transistor 7024 is set with the
adjustable voltage divider of R3066, R3068 and R3070. The
level at which this happen, is controlled by the DAC6 line, and
is dependent of the “sharpness meter” reading in the Auto TV
program, the picture tube size, and the sharpness setting by
the customer.
CL 16532149_088.eps
131201
Differen-
tiator
Coring
To
SVM
coil
To
SVM
coil
Matrix
Output
stage
Coring
Differentiator
slope
Transition
No coring
R
G
B
Scavem
action
CL 16532149_089.eps
131201
Differen-
tiator
Coring
Clipper
To
SVM coil
Matrix
Coring
Differentiator
slope
Transition
R
G
B
TDA8444
DAC7
DAC6
DAC5
DAC4
DAC3
DAC2
DAC1
DAC0
I
2
C
Gain
Parabola
modulation
Output
stage
Parabola
Deflection
pulses
Reserved for
future use
Scavem
action
Clipper
(fixed)
RES
11V8
7V7
9V4
8V7
0V
6V9
7V9
2V6
1V9
MATRIX
DIFFERENTIATOR
SC4
100n
2010
SC5
3
BBY40
6002
1
560R
3038
68K
3030
7010
BFS20
39K
3022
1K8
3018
22K
3028
22n
2008
Y_SCAVEM
(FROM SSB)
DAC7
+12S
7008
BF824
100n
2006
47K
3026
3
6000
BBY40
1
1K8
3032
BFS20
7012
47K
3040
2K2
3034
1K
3044
560R
3020
6K8
3042
12K
3024
7006
BFS20
3K3
3036
CL 26532041_082.eps
230402
TO 'CORING/CLIPPING'
0V
11V8
11V
0V8
RES
0V
11V8
CORING / CLIPPING GAIN
BF824
7014
3054
2K2
3048
1K8
22n
2020
7020
BF824
3062
2K2
BFS20
7022
2014
22n
560R
3050
3058
680R
3064
15R
3046
1K8
3068
680R
7018
BFS20
SC6
SC7
22n
2012
12K
3066
3056
2K2
BFS20
7016
3052
560R
10p
2018
3p3
2016
3060
680R
CL 16532149_091.eps
201201
DAC7 DAC5
DAC6
11V8
6V9
6V2
0V
0V3
7024
BFS20
100R
3074
1K2
3076
SC8
BFS20
7026
1K5
3072
1u
2022
3078
1K
TO 'PARABOLA MODULATION'
FROM 'DIFFERENTIATOR'
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