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5.3 MUTING CIRCUIT
Muting Gate
The LINE OUTPUT muting gate is incotporated
in IC401 (H412006), the output being muted
when pin 15 of this IC is at L level and pn 2 at
H level.
Pin 15 is connected to the PLAY output of the
operating mode control IC (8A843) and is switch-
ed to H level only during playback mode. +B is
applied to pin 2 vn R478 and, R477, and the pin
is kept at H level except when Q426 is turned on
during recording mode. In this way, the line output
is muted during fast forward, rewind, stop and
play pause modes, and cancelled during playback,
recording and recording pause modes.
Fig. 5-12 LINE OUTPUT mutins
The recording amplifier input muting gate is
gloundconnected by transistors (Q103 and Q104).
The bases of these hansistors are connected to pin
2 of HA12006 via R145, R143, R428, D427,
D429 and R477, thereby enabling muting to be
cancelled during recording mode. fhrring rec mute
mode, however, these bansistors are turned on,
resutling in the recording of blank sections of tape.
BEC AMP
D4æ D427
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lC4O2Pin 14
Pinch solenoid
Head base
MS solenoid
F F s o l e n o i d
1 C 4 0 3 P i n 6
1C403 PinS
Fig. 5-10 MS operation timing chart
Auto-Stop Circuit
This circuit is used to switch the mechanical
drive conbol IC (BA843) to stop mode when tape
transport stops (see Fig. 5-11). A photo-intemrpter
is used for tape transport detection, and the rotary
blade mechanism used to intemrpt the light beam
is coupled to the take-up reel by belt.
During Tape Transport
1. Q401 is turned on and off repeatedly by the
photointernrpter output, resulting in C403
being charged up and discharged again in re-
peated cycles.
When Tape Transport Stops
When the take-up reel stops at the end of the
tape, Q401 ceases switching on and off due to
the loss of the photo-intemrpter output.
With a current being passed from +B to C4O3
via R405 and R406, C403 is charged up and
the Q402 base potential increases, resulting
in Q402 being turned off. Q403 is thus turned
on and pin 2 (STOP) of.tC402 is switched to
L level, thereby switching the deck to stop
mode.
I C 4 0 2
( O - P L A Y ,
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FiS. +t 1 Auto-stop circuit
F i g . 5 - 1 3 R E C A M P m u t i n g
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