JVC CD-1920 User Manual

Main Parts Location
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Fig. 3
New Technique
The multi-point peak level indicators let you know the
precise levels of the peak signal pulses that the mechanical
VU meters cannot follow. They are essential aids for
making good recordings, for they allow recording at
maximum levels without exceeding the magnetic saturation
level of the tape. During adjustment, sine waves are used
and the indication of the VU meters corresponds to that of
the peak level indicators. But, for ordinary musical signals,
the VU meters usually indicate lower values because of
their slower response.
oro na a = = =
O !
L-CH ! Power supply
Input H . | terminal
terminal I re Da404aP I Vcc=5V
R-ch
H
“
x
Light
Emitting
{
Input
I
Diode
(LED)
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terminal Mecsas es Se es Se 4
Fig. 4
CD-1920/A/B/C/E/U
No. 4142
MIC jack circuit board
Main amp circuit board
Peak level circuit board
DIN jack
PIN jacks
ANRS circuit board
Power transformer
Power supply circuit board
Motor ass’y
Cds lamp
Flywheel ass’y
Head wire terminal circuit board
Air-damp pipe
Level meter (Right)
Indicator circuit board
Level meter (Left)
OONOoORWN =
The left and right channel inputs are individually rectified
and the capacitor C is charged by the higher of the left and
right channel signal levels. The variable resistor VR adjusts
the lighting level of the LED. When no input signal is
available, the transistor X is conducting because base
current is applied through the resistance. At this time the
output terminal of the IC TD3404AP is at a high level (5V),
providing no current to the LED, which does not light up.
When the base potential of the transistor X is reduced to
below 0.6V by the input signal, X becomes non-conducting,
the IC output is at a low level (OV) and current flows to the
LED and lights it up.
The multi-point peak level indicators consist of five of the
circuits encircled by the broken line, connected in parallel.
Each of the VRs is adjusted according to the signal level at
which the LED lights up to indicate.
A circuit which, with high level inputs, provides low level
outputs and vice versa, such as TD3404AP, is usually called
an inverter. This 1C TD3404AP, widely used in computers,
is a digital |C which includes six such inverter circuits, five
of which are used in this set.
For easy use, the peak level indicator circuit of this set is so
designed that the higher one of the right and left channel
signal levels is detected to light the LED. The attack time is
established at about 4msec, achieving both easy visibility
and indication accuracy.
For adjustment, see the section ‘“ADJUSTMENTS” on page
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JVC CD-1920 Specifications

General

Brand	JVC
Model	CD-1920
Category	Cassette Player
Language	English