Toshiba D-VR3SU Service Manual page 137

(2) Block Description
1) Input Selector
Input selector outputs 1 signal from 4 different signals received. It outputs 1 selected signal from tuner,rear,front.
2) Normal(Linear) Selector
Two signals,L-CH and R-CH are inputed to Hi-Fi IC.But,linear audio is capable of receiving only one signal.Therefore,the
2 input signals must be selected. Usually,the outputs are mixed signals of L-CH and R-CH unlike the input selector,the
normal selector does not amplify the selected signal.
3) Output Selector
It selects to output Hi-Fi L-CH,Hi-Fi R-CH,LINEAR and MIX(Hi-Fi+LINEAR) signals with the final output IC
pin 78 (R-CH) and pin 80 (L-CH).
4) Output ALC(Convertor)
ALC is used because when the input level of RF converter gets bigger,it shows up as noise on the screen. But,this block is
not used this model(ALC OFF)
5) PNR(Peak Noise Reduction)
It is a type of emphasis,de-emphasis function to eliminate noise during modulation /demodulation PNR operates as that of
VHS FORMAT to reduce noise.
6) Audio Limiter
Before modulating the signals from PNR block,it limits signals exceeding the size limit to max deviation of +/- 150KHz.
7) VCO(Voltage Control Oscillation)
It is a modulation functionthat oscillates 1.3MHz (L-CH) and 1.7MHz (R-CH).
8) RF LPF
It is a function to eliminate the harmonic components of Hi-Fi carrier formed during VCO,which may affect other block.
It's pass-band approximately 2MHz.
9) MIXER
It mixes the Hi-Fi carrier formed in L-CH and R-CH. However,due to the frequency difference between L-CH and
R-CH,when equal amount of R-CH is recorded to tape,R-CH is must smaiier than L-CH.
Therefore,the R-CH output is approximately 10dB bigger than L-CH.
10) Current Amp
It is the final amplifier of the mixed Hi-Fi carrier IC pin 28's resistance controls current, which change the size of IC
pin 26.
11) AGC(Auto Gain Control)
It maintains uniform size of Hi-Fi envelope,which is inputed by pre-amp in play back mode.
12) BPF(Band Pass Filter)
L-CH and R-CH each has BPF. The center frequency is same as carrier frequency.
It is used to receive only Hi-Fi carrier from all signals inputed to pre-amp.
Circuit Operating Descriptions
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