3. Analysis of common path circuits
High frequency television signals, received via an antenna (or transmitted through a
cable TV system) to the input terminal of the high frequency tuner TU101 (TECC7949),
are processed for tuning and high frequency amplifying and mixing, then a 38MHz image
intermediate frequency and 31.5MHz sound intermediate frequency signal will be
released at the IF terminal of TU101 to (1) of the thickfilm circuits N101 (M9911A), where
signals are amplified to compensate for the insertion losses of the sound surface wave
filter. Single or dualended input is used for the sound surface wave filters SF101
(K6265K) of this appliance according to system properties. Single or dualended input is
controlled by CPU N901 (12) through V101 (BC548C). D/K, B/G, I signals are for
singleended input and M signals are for dualended input. The sound surface filter
K6265K functions as a wide band wave filter, suitable for D/K, B/G and I sound signals, if
the input is singleended. Dualended input is for a narrow wave filter, suitable for M sound
signals. Intermediate frequency signals will be transmitted to (48) and (49) of N201
(TDA8844) after the sound carrier frequency is trapped by the sound surface wave filter.
The AGC time constant is dependent on C243 (lu) connected to (53) of N201(TDA8844),
2
and the AGC is controlled by I C busmastering and output through (54) of N201
(TDA8844) to determine the high frequency tuner increase.
4. Analysis of secondary sound intermediate wave filter and wave trap selection switch
circuits.
Video combined television signals output from N201 (6) of (TDA8844) through the triode
V203 and/or V204 is transmitted to the wave filter Z202Z205 and trap Z207Z210,
respectively.
Some combined television signals through C212 are filtered through the diode. The diode
positive voltage VD201VD204 is 4V, and the negative voltage is controlled by (5) (8) of
CPU N901 sound system control terminal through a 1K resistor. When one CPU base
pin has a low electrical value, the corresponding diode is energized and the combined
television signals form the secondary sound intermediate signals through a
corresponding wave filter (Z202 or Z205) before being transmitted to (1) of N201
(TDA8844) through V202.
50
High pressure tracing and circuit
breaker input
2.5
23.1K
22.8K
51
Capacitor connection from field
tooth wave
3.8
6.2M
4.6M
52
Field reference current formation
3.9
39.0K
39K
53
AGC decoupling
4.3
6.2M
4.6K
54
RF AGC output
1.9
4.8K
4.8K
55
Audio frequency connection
without aggregation
2.9
4.5M
4.6M
56
Sound demodulation and
decoupling
2.3
6.2M
4.6M
17
