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6. Analysis of sound and bass power amplifying circuits
Sound power amplifying circuits are composed of integrated circuits TDA7297 and
peripheral components. TDA7297 is an integrated electrical circuit for muting and power
for double track stereo sound power amplifying with an output power of 15+15W. The
output of TDA7297 for sound is BTL and no decoupling capacitor is used in the output
circuits. A wide band (6V~18V) power supply incorporates circuit breaking and overload
protection. Sound signals from left and right tracks are transmitted from (18) and (15) of
the integrated circuit N701 for sound acoustic effects processing adjustment through
R604, R603/607 and R606, respectively, and coupled to (4) and (12) of the sound power
amplifying integrated circuit N601 through C601 and C605, and then both positive and
negative signals are transmitted through (1), (2), (14) and (15) after being amplified to
directly activate the speaker.
Information introducing functions and testing data for TDA7297 maintenance is listed in
Table 4. Test information is listed beneath VHFL, if a cylindrical color card is installed then
a FLUKE 79 III meter is used.
7. Analysis of field sync and field scan output circuits
The field sync signals segregated from compound sync signals are used to activate the
field frequency segregation system which commences when a set amount of field sync
pulse signals are tested. Of the sync pulse frequencies obtained from segregation, some
are transmitted to the field tooth wave generator. The field frequency tooth wave, after
Table 4
Grounding Resistance
(R)
No.
Function
Working
Voltage (V)
Positive
(
¦¸
)
Negative
(
¦¸
)
1
Right track sound output
8.0
12.8K
12.7K
2
Right track sound output
8.0
12.8K
12.8K
3
15V power supply
16.0
~
0.94M
4
Right track audio signal input
1.5
86.2K
86.6K
5
Neutral point
0
~
~
6
Mute signal input
3.8
108.8K
107.6K
7
Power signal input
4
5.6K
5.6K
8
Grounding
0
0
0
9
Grounding
0
0
0
10
Neutral point
0
~
~
11 Neutral point
0
~
~
12 Left track audio signal input
1.5
86.3K
86.5K
13 15V power supply
16.0
~
0.94M
14 Left track sound output
8.2
12.7K
12.7K
15 Left track sound output
8.2
12.7K
12.7K
20