Daewoo DV-K884N-SJ, Service Manual

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4) Signal Flow & Operation in Record/Playback Modes
Figure 7 shows the flow of signal in Record & EE mode.
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Record mode
• TV In, Line In 1/2/3 can be selected by Bus Data. The line 2 & 3 are used for BS monitor input, and L CH of Line In 3 for SAP (Sub
Audio Program) input.
• Hi-Fi input signal's noise is reduced in PNR circuit through EVR (Electronic Volume Resistor), and modulated to FM, and output
through port 22.
• There are three modes in EVR: Through, Manual and ALC. All of them are selected by Bus.
• In Manual mode, EVR gain can be controlled by adding voltage to R CH 40 and L CH 42. In ALC mode, EVR gain is automatically
controlled together with maximum signal.
• The modulator of these models adopts a Voltage Control Oscillator (VCO) especially with good linear performance. The center fre-
quency of VCO is adjustment-free thanks to Zener Zap method.
• The center frequency of TA1246F is /– 5Khz regardless of NTSC or pal, and both L CH and R CH of recorded FM signals
are mixed and output through port 22.
• The mix degree of L CH and R CH can be controlled by Bus Data step by step.
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EE mode
The signal through EVR can select mode and channel by Bus Data in Output Selector and they will be output to Line Out and Monaural
Out respectively. Maximum signal level is adjusted by ALC circuit in Monaural Out.
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Normal Audio
Normal Audio IC's signal, out of Input Selector, is output through port 35. An output mode of Mix, L CH and R CH is selected by Bus
Data. Line 3 In (L CH) should be selected for SAP output. Meanwhile, signal out of normal audio is input to port 31 and then output to
Line Out and Monaural Out after passing Output Selector Circuit.
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Playback mode
Figure 8 shows the flow of signal in Playback mode.
• The Playback FM signal input by port 25, passes AGC AMP in order to compensate the level difference of rotating head, and L CH
and R CH are separated in BPF. The center frequency of BPF is controlled to match with that of VCO.
• Then, the signal is demodulated and passes through Switching Noise circuit. Finally it is input to Output Selector after reducing noise
at PNR circuit.
Line IN
TV IN
33k
27k
1µ
IC Pin NO.
120k
Vref
Input
Selector
8dB
Y
!
%
u
I
O
P
{
}
EVR
ALC
Norm.
Audio IC
R
Output
Selector
9dB
PNR
Y
9
1
3
‘
ALC
Monaural
Line Out
Rec FM Out
Mod
Monitor
Through
Norm. Audio Out
Fig. 7 Block Diagram of Record and EE Mode
Output
Selector
ALC
R
1
3
9
Q
BPF Demo.
SW. N.C
PNR
FM
AGC
PB FM IN
Norm. Audio IN
9dB
Line Out
Monaural Out
Fig. 7 Block Diagram of Playback Mode