Pioneer KEX-900 Service Manual page 23

© Spectrum Analyzer Circuit (KEX-900)
e706" KHATOS
ALC
IC705 : MBIS04L
5
L-cH=> + a
= mu
6
\C 707
CONTROL INPUT PIN SN-CONNECTED
to PIN
9
H L L
cio
H H u 12
L u H 1
i
FL TUBE
2780 icgot
PD4091 peratd
pay
hed
ie
2
SYSTEM CONTROLLER
Audio signals are divided into seven frequencies, and their
power level is displayed sequentially.
The L and R output signals of the mixing amplifier (IC601) are
combined and input to the ALC circuit (IC705). The audio
signals, whose levels are adjusted by IC705, are separated
into the following 7 frequencies via the IC706 band pass
filter: 63 Hz, 120 Hz, 250 Hz, 500 Hz, 1 KHz, 3.5 kHz, and 10 kHz.
Itis further rectified into DC voltage by the IC's internal recti-
fier. Each signal is selected by the multiplexer (IC707) which
is controlled by the deck controller (IC701). The signals will
become 0 V to 4 V through the level shift circuit (IC708 2/2).
These signals are input to pin 2 of the comparator circuit
(IC708 1/2). Pin 3 is of standard voltage. The digital signals of
pins 24 to 31 of the deck controller (IC701) add the voltage
converted by 1B702's D-A convertor circuit. The A-D convert-
ed signals converted by IC708 1/2 are input to the deck
controller's pin 18. The power level of each frequency is then
displayed on the FL tube.
The relation between the standard voltage of 1C708's pin 3
and 1C701's pins 24 to 31 is shown in Table 1.
a
4 => Gi-[ele)]. <=> Gia ale)
MULTIPLEXER
C707 : TC4051BF
LEVEL SHIFT COMPARATOR
IC708(2/2): HAI7358 = IC708(1/2) : HAI7358
wet!
©)
C701 -.
PD3069B 7 2 aoe
ee
DECK CONTROLLER
Fig. 11
C Voo=5.5V)
Table 1
25