Akai VS-2EGN

© Fig. 7-131 shows the principle of the input circuit.
The tuned circuit has a tapped inductor and a tapped
capacitor in order to obtain a high ‘TR’ and also to con-
veniently match the impedance of input and output.
INPUT
Fig. 7-131 Principle of input
circuit
@ The LOW-CH and HIGH-CH circuit configurations
which are produced by the action of the switching diode
are as shown in Figs. 7-129 and 7-130. During HIGH-CH
reception, La4 is inserted in parallel with La3, to reduce
the inductance and C15 is eliminated, so the capacitance
is made smaller and a higher resonant frequency is a-
chieved. Resistors R30 and RD inserted in parallel with
La3 and LaS respectively are damping resistors for con-
trolled damping of the circuit TR. When the TR is too
EFFECT OF WAVEFORM
DEVIATION IS GREAT
Fig. 7-134 High TR
© Fig. 7-136 shows the IF trap characteristic (See Fig.
7-128).
RESPONSE —>
FREQUENCY(MHz) —>
Fig. 7-136 IF trap characteristic
3
poorer > -€ or
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Fig. 7-132 Resonant
RESONANCE , .__! _
FREQUENCY | 27VLC
Fig. 7-133 Frequency
circuit response
high, variation of the frequency response characteristic
between the channels becomes too large, and adjustment
becomes difficult.
Circuit load TR can be expressed as follows:
TR=@L/R
where L=total inductance of the tuned circuit.
Response when there is no damping resistor.
Response when there is damping resistor.
SMALL EFFECT
Fig. 7-135 Low TR
Service Manual VS-2EGN
86