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Muting at FF, REW, and STOP (Fig. 16)
This circuit prevents unwanted noise (for in-
stance, motor noise) at FF, REW and STOP.
1. When the set is in the STOP state, or the FF
or REW button is pushed, MUTING switch Sz is
set to the ON side.
2. +Bt is supplied to Qoo+ (Qoor) through the route
S r > R E C s w i t c h S r r , R z a z ' D o o r > R o t + ( R o t t )
> Doos (Deoz) + Qooa (Qeo:), and Qooa (Qoor) is
tumed ON.
3. \ilhen Qooo (Qoo:) is tumed ON, the signal
current of both the L and R channels flows to
ground and is muted.
Recording muting (Fig. 16)
REC switch Srr is ganged ïvith the REC button.
Mechanical muting is provided so that Sr r is opened
after the REC/PB switch Sz has been switched
when the REC button is pushed, and Sz is switched
to the PB side after Srr has been closed when
returning to the STOP state after the REC button
is pushed. Noise produced when the REC button
has been pushed, and noise produced at REC *
STOP and REC/PLAY > STOP are muted by the
timing of these actions and the muting circuit
consisting of Qoor to Qoo+ and Qroz.
In the STOP state, the MUTING switch Sz is at
the ON side, and since +Br is applied through the
route Sr t Srr t Rzoa t Duor > Rrrs t Q:oz, the
recording amp signal is muted.
When the PLAY
button is pushed, +Bz is
supplied through the route Sz ' Rrts' Qroz, Qroz is
tumed ON, and the muting amp signal is muted,
the same as at the STOP state. When the REC
button is pushed, Sz is switched to the REC side,
Qroz is turned OFF, and the signal enters the
recording amp. Noise produced by switching is
preventeâ by turning Qroz ON and OFF in this
manner.
Muting at follow-on recording (Fig. 16)
This is the muting
circuit
when follow-on
recording by pushing the REC button from PLAY
operation.
t. Wtren the REC/PB switch Sz is switched from
the playback side to the recording side, +Bz is
tnppti"d through the route Rotz' Doos > Coos >
R o o s t S z t g r o u n d .
2. The base potential of Qooz is dropped and Qooz is
tumed ON dudng the charging time of Coos'
3. When Qeoz is turned ON, Qooa and Qooc are also
tumed ON, and muting is actuated' The muting
time is determined by the time constant of
Coos and Roos, and is set at approximately 0'5
second.
cT-F7clcl
4. When Sz has been switched from the playback
side to the recording side, +Bz is supplied
through the route Rotz t Doo+' Coo+' Rooz t Sz t
ground.
5. Qooz is turned ON during the charging time of
C oo+.
6. When Qooz is turned ON, muting is actuated as
described in item 3 above. However, the muting
time is determined by the time constant of Coo+
and Rooz.
6 . 5 C O N T R O L C I R C U I T S
AUTO STOP circuit (FaS.17l
This circuit automatically releases the mechanism
by means of a solenoid when running of the tape is
detected and the tape has been stopped with the
mechanism in the FF, REW or PLAY (REC) state.
Running of the tape is detected by coupling
a Hall element detector switch to the take-up
reel turntable with a belt. Since Czor is charging
during normal operation, Qroz is turned OFF,
and is unrelated to the AUTO STOP operation.
When tape is running
When the PLAY (FF, REW) button is pushed,
the MOTOR switch Sa is switched to the ON side'
and the MUTING switch Sz is set to the OFF side
(to the ON side at FF and REW). Moreover, since
the PAUSE button Ss is not pushed, it is at the
OFF side.
1. While the tape is running the base potential of
Qzor is changed as illustrated in Fig. 1? @,
by switching of the HalI element-
2. This change is taken from C'to+, rectified by Dzoa
and is used to tum Qzor ON and OFF.
3. Croo is charged through the route +Bz + Rzt+ >
Ctoo , ground, but since Qro: is tumed ON and
OFF. the'anode voltage of Dzoa is varied as
illustrated in Fig. 17 @.
4. +Bz is divided by Rrzr and Rzzo and applied to
the base of Qzo+ through Dzto' Rzrr. It is also
applied to the emitter of Qroe through Rzrr'
Therefore, Droa is reverse biased and turned off,
and Qro+ is turned OFF.
5. When Qzoa is turned OFF, there is no voltage
drop across Rzto, and Qzos is zero biased and
turned OFF.
6. Consequently, since Qroz is zero biased, it is
tumed OFF and current does not flow to the
solenoid.
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