Daewoo DV-K884N-SJ, Руководство по обслуживанию

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5) Operation of Main Blocks
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Input Selector
It selects one of TV In, Line In 1/2/3 by Bus Data. And also, it selects output of Normal Audio IC.
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Output Selector
It selects output mode each of Hi-Fi/L CH/R CH, Line 2/3 monitor by Bus Data.
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EVR (Electronic Volume Resistor)
It controls audio record level by the voltage of port 40/42.
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Hi-Fi ALC
It automatically controls level by EVR AGC mode selected by Bus Data, which also makes signal not be out of spec. Attack & recovery
time of ALC is set by the constant of port 44.
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VCO (Voltage Control Oscillator)
VCO with good linear performance is used for these models. Center frequency of carrier does not require adjustment thanks to Zener
Zap. Tolerance is +/– 5Khz of center for both L CH and R CH regardless of NTSC and Pal.
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Switching Noise Compensation
It compensates noise happened at rotating head. Compensation pulse is made by the constant inside of IC.
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DOC (Drop Out Compensation)
If playback FM signal is under 4 microsecond, dropout is detected and compensated, i.e., playback audio signal is adjusted close to Vref
(Voltage Reference) from the dropout detect point. It names 'Smoothing Mute'.
The delay time for dropout is 18microsec and its detect level is –20dB.
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Envelope Detection
It is used for adjusting tracking of head. It detects the Envelope Detection of playback FM signal after passing BPF. Channel of
Envelope Detection (L CH or R CH) is selected by Bus Data.
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Hi-Fi Detection (Forced Normal)
If dropout of playback of FM signal is 70 microsecond, non Hi-Fi is detected and port 27 comes to be high. Under this condition, audio
output of Line Out is compulsorily changed to Normal Audio.
The delay time of detection is 1.6 microsecond which is set by constant together with detection time.
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Monaural ALC
There is an ALC circuit on Monaural Output of port 19 apart from Hi-Fi.
Attack and recovery time are set by constant of port 21. If port 21 is grounded, ALC mode will not work.
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AUX Audio Mute
TA1246F has two Mute functions. One is Bus Mute which stops signal by Bus Data, and the other is AUX Mute which is operated by
voltage applied from the outside. A Mute transistor, which does not need power of IC, is used for AUX Mute. Voltage addition to port
10 make Mute function possibly operated even without power of IC. (Mute TR cannot be controlled by Bus.)
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Log Amp
It is used for Audio Level Meter. If Bus Mute or AUX Mute is on, nothing is usually output.
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Just Clock Mode
It makes it output of Log Amp possibly used for Just Clock Mode (Adjustment to standard exact time). It is set by Bus Data.
If Just Clock Mode is set, L CH output of Log Amp will not work even though AUX Audio Mute is on (Bus Data is off).