AIWA
J
CS-880H,HG,U,UC
4. Other Circuits
4-1.
FM/AM +B Power Selector Circuit
IC 2
T C 4 0 I IB P
4-2.
Scan Auto Stop Circuit
to RADIO
VOLTAGE CONST. <+B>-
F ig.9
Switching is performed with a 4-NAND gate IC (IC2).
TERMINAL
NAME
at FM
at AM
FM
10
P
4
)
i_n_
JTJ"
AM
IOP3)
n r
TIL
COM
Ul_
1TL
02 0 BASE
HIGH LEVEL
J
l
W
l e v e l
Fig. 10
When the FM band selector key is depressed, pulses with the
same phase are fed out to IC3 (MSG5829G) DP4 and COM.
As this output passes through the NAND gate 1C (TC4011BP),
a high level output is produced at NAND gate 1 output and this
causes Q20 to turn ON. As a result, 019 turns ON and the FM
+B is obtained. With AM reception, no output appears at DP4,
the NAND gate 1 output is set to the low level and with 020
O FF, 018 turns ON and the AM +B is obtained.
► To SD P IN
Fig. 11
4-2-1. Operation During FM Reception
The S-curve output pin 10 and meter output pin 15 of IF 1C
(IC2, HA12413) are used. If pin 10 has a voltage where V (B )
< V(10) < V (A ) with respect to the preset point A and point
B voltages (about ±0.5 V with respect to pin 10 voltage during
tuning), no output appears at point (C) and when there is an
output at pin 15, point (F ) is set to a low level and no signal
is fed out to point (C). A trigger pulse is produced at point (G)
by the above two AND circuits, this is applied to the SD pin
of the controller IC and the scanning is stopped.
4-2-2. Operation During AM Reception
The IF output from pin 12 is smoothed and point (F ) is reduced
to the low level by the output. As with FM reception, a trigger
puise is produced at point (G) and the scanning stops. [IC3
(NJM4558D) does not work during AM reception.]
5. Dynamic Super Loudness (DSL) Circuit
If the D SL circuit is compared with the loudness circuit, it is
seen that both function to boost the low-range (bass) and high-
range (treble) frequencies with respect to the midrange fre
quencies but there are the following major differences.
5-1.
Characteristics
OUTPUT
FREQUENCY
Fig. 12
The loudness system functions to boost the midrange frequencies
too. However, the D SL system keeps this increase down to the
bare minimum.
With the loudness system, the characteristics do not change with
the strength of the signal entering the volume control for provid
ing a tape in the control {normally scale unit 5 (center posi
tio n )], and the volume control's tap position is mechanical,
25
