Sansui 8900ZDB - Page 20

9900Z/8900ZDB/79002
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A. UP-Pulse Generation in FM Mode (Clockwise Rotation of
Tuning Knob) (See Figs. 2-2 (a), 2-3, and 2-4.)
When the tuning knob is rotated clockwise, the photo-couplers
fPH51 and fPH52 output the pulses as shown by Fig. 2-2 (a). The
output pulses (A) and @®) from fPH51 and fPH52are inverted through
£Q51 and fQ52, respectively.
The inverted output pulses © and © are waveform-shaped through
{Cla and IC1b (inverters) and then outputted from the output gate
of Pin No. 10 of 1C1a and the output gate of Pin No. 4 of IC1b re-
spectively, as two inverted output pulses © and ©.
The inverted output pulse © from 1Cla and the differentiated pulse
@ of the inverted output pulse ® from 1C1b are inputted to IC1d,
and a pulse ® is outputted from the output gate of Pin No. 11 of
ICid.
The inverted output pulse © from IC1b and the differentiated pulse
© of the inverted output pulse © from IC1a are inputted to IC1c;
however in this case, no pulse is outputted from the output gate of
Pin No. 3 of IC1c but a constant H-level (in voltage) output signal |
is kept outputted.
Next, in FM mode, since a constant H-level voltage is applied to the
input gate of Pin No. 9 of IC2a and the input gate of Pin No. 6 of
IC2b, the inverted output pulse ®) of the pulse © is outputted
from the output gate of Pin No. 10 of IC2a, and the inverted output
pulse © of the pulse © is outputted from the output gate of Pin
No. 4 of IC2b.
The inverted output pulse (K) from IC2a and the differentiated pulse
® of the inverted output pulse © from 1C26 are inputted to !C2d,
and a pulse is outputted from the output gate of Pin No. 11 of
1C2d.
This pulse ®) from 1C2d and the output pulse ® from IC1d are
combined into an UP pulse Q.
The UP pulse @ is next current-amplified through fQ53 and input-
ted to the terminal UP of TC9140P (fIC1) to increase (UP) the fre-
quency to be received.
Further, the inverted output pulse © from IC2b and the differen-
tiated pulse (@) of the inverted output pulse ® from 1C2a are in-
putted to 1C2c; however, in this case no pulse is outputted from the
output gate of Pin No. 3 of IC2c but a constant H-level output signal
© is kept outputted.
B. DOWN-Pulse Generation in FM Mode
(Counterclockwise Rotation of Tuning Knob)
(See Figs. 2-2 (b), 2-3, and 2-4.)
When the tuning knob is rotated counterclockwise, the photo-
couplers fPH51 and fPH52 output the pulses as shown by Fig. 2-2
(b). In this case, the output pulse from fPH52 leads the output pulse
from fPHS1 by a phase angle ‘of 90 degrees.
Therefore, there is a difference of 180 degrees in phase between the
output pulse from fPH52 when the tuning knob is rotated counter-
clockwise and the one when rotated clockwise against that of the
output pulse from fPH51. Asa result, the inverted output pulses ©
and ©) are outputted from !Cla and !1C2b respectively. The inverted
output pulse ® from IC1b and the differentiated pulse © of the
inverted output pulse © from ICla are inputted to ICic, anda
pulse) is outputted from the output gate of Pin No. 3 of IC1c.
The inverted output pulse © from Cla and the differentiated pulse
® of the inverted output pulse ® from IC1b are inputted to ICid,
however, in this case, no pulse is outputted from the output gate
of Pin No. 11 of 1C1d but a constant H-level output signal() is kept
outputted.
Next, the inverted output pulses ® and O of both pulses, (E) and
© are outputted from the output gates of Pin Nos.10 and 4 of 1C2a
and IC2b, respectively.
The inverted output pulse ©Ofrom 1C2b and the differentiated pulse
(OD) of the inverted output pulse ® from !1C2a are inputted to IC2c,
and a pulse © is outputted from the output gate of Pin No. 3 of
IC2c. :
This pulse © from IC2c and the output pulse (1) from ICl1c are
combined into a DOWN pulse ®. The DOWN pulse ®) is next
current-amplified through fQ54 and inputted to the terminal DOWN
of TC9140P (fIC1) to decrease (DOWN) the frequency to be re-
ceived.
Further, no pulse is outputted from the output gate of Pin No. 11
of IC2d but a constant H-level output signal ®) is kept outputted.
C. UP- and DOWN-Pulse Generation in AM Mode
In AM mode, since the input gates of Pin Nos. 9 and 6 of 1C2a and
1C2b are in a constant L-level signal in voltage, the output gates of
Pin Nos. 10 and 4 of I[C2a and IC2b are also in a constant H-level
state in voltage, respectively, regardless of the input conditions of
the input gates of Pin Nos. 8 and 5 of IC1b and !C2b.
Therefore, a constant H-level signal is inputted to the input gates of
Pin Nos. 2 and 12 of IC2c and IC2d, respectively; however, since a
capacitor C is connected to the other input gates of Pin Nos. 1 and
13 of IC2c and IC2d respectively, the H-level signal is not inputted
but a L-level signal is inputted to the input gates of Pin Nos. 1 and
13.
Accordingly, the output gates of Pin Nos. 3 and 11 of I1C2c and IC2d
are in a H-level signal in voltage without outputting the UP and
DOWN pulses.
In other words, when the tuning knob is rotated clockwise in AM
mode, the UP pulse is the output pulse(J) from IC1d, and when the
tuning knob is rotated counterclockwise, the DOWN pulse is the
output pulse) from ICtc.
That is to say, the number of the UP or DOWN pulses in AM mode
is half of that in FM mode. This UP pulse D or DOWN pulse(1)is
inputted to the terminal UP or DOWN of TC9140P (fIC1) to in-
crease (UP) or decrease (DOWN) the frequency to be received.
When
the
UP
or
DOWN
pulse
is
inputted
to
the
terminal
UP
or
DOWN
of
TC9140P,
the
frequency
to
be
received
changes
by
100
kHz
(50
kHz
in
Europe)
per
pulse
in
receiving
FM
frequency
or
by
10
kHz
(9
kHz
in
Europe)
per
pulse
in
receiving
AM
frequency.
In
addition,
the
pulse
width
of
the
UP
or
DOWN
pulse
can
be
de-
termined
by
a
time
constant
of
the
capacitor
C
and
the
resistor
R
provided
in
the
respective
differentiator
circuits.
2-3. Muting Operation
In selecting AM/FM band, when depressing the manual. UP/DOWN
key (the tuning knob in 9900Z and 8900ZDB), or when performing
the automatic search operation, the mute signal from the mute
outpyt terminal of Pin No. 36 of the PLL synthesizer control IC/
TC9140P (fIC1) changes to H-level in voltage to begin the muting
operation.
This mute signal controls the tuner output in FM/AM mode by turn-
ing dQ16 ~ dQ18 ON or OFF in FM mode and eQ5 in AM mode.
In FM stereo mode, the mute signal from Pin No. 12 of the decorder
1C/HA11225 (dIC2) is used for the muting operation, in addition to
the mute signal from fIC1. However, only the mute signal from fIC1
is used for the muting operation in monophonic FM broadcasting
and AM modes.
Fig. 2-2 fPHS1/fPHS2 Output Pulse
fPH51
fPH51
fPH52 fPH52
E
I
= Pe anhase Angle 90°
|
ass {7 Phase Angle 90°
[oJ
{a) Clockwise Turn of Tuning Knob {b) Counter Clockwise Turn of Tuning Knob