Akai GXC-750D

人
3.
12
PLAY PLUNGER OPERATING CIRCUIT
1) This circuit starts Play Plunger operation by
supplying a large amount of electric сштеп апа
then maintains the operations, once it's started,
by а small electric current. This deck is transistor
driven and does not employ relays. It operates on
a plus-minus power supply.
2) When the deck is set to PLAY mode, IC4 output
terminal (3) of the system control circuit reaches a
high level and C26 is charged through R79, C25
and R82. But since the charging time of C25 is
shorter, its terminal voltage is increased faster than
that of C26 and is added to TR3 base through
power supply circuit D12 and D11. TR3 turns ON,
and C10 charging current flows as R1 > R2 > C10
э ТЕЗ. While C10 is charged, TR2 base electric
potential decreases to turn TR2 ON and the
Darlington" connected TRI base electric potential
also decreases to turn ТЕ! ON. Thus the Play
Plunger is supplied with voltage of ® electric
potential and © electric potential and starts
operation.
Now, when charging of C26 is completed, C26
terminal voltage is added to TR6 base of the
power supply circuit. TR6 is thereby turned ON
and D9 anode terminal becomes ground electric
potential. When that happens, D7 cathode termi-
nal becomes lower than the ground electric
potential and turns TR4 ON. For this reason, even
when TR2 and TRI is turned OFF after charging
of C10 is completed, electric current flows to the
Play Plunger from © power supply through
ground > ТВА > рб > R4 to maintain operation.
3) Because the Play Plunger Operating Circuit is on a
plus-minus power supply of C5 and C6, when the
power switch is turned OFF during PLAY mode,
condenser C5 discharges faster than C6 due to the
fact that the load of C5 on the Ф side is larger
than Сб.
This causes the pinch roller to stay in contact with
the capstan for a little while after the reel motor
have stopped, and results in loose tape coming
out of the cassette pack due to the flywheel
inertia, In order to prevent the malfunction, Play
Plunger is disengaged, simultaneously, when the
reel motors are stopped by the discharge of C5.
When the power switch is turned OFF at PLAY
mode, C5 discharges faster than C6 and the reel
motors stop. At the same time, since the condition
between TR7 base and R13 can be thought of as
OPEN, the C6 leftover © electric potential is
added to TR7 base and TR7 is turned ON. There-
fore, D7 cathode becomes ground potential, TR4
is turned OFF, and the electric current stops
flowing to the Play Plunger to disengage it.
4. OPERATION TIMING WHEN PLAY MODE
IS EFFECTED FROM FAST FORWARD
OR REWIND
1) When the PLAY mode is effected from Fast
Forward or Rewind, if the Play Plunger functions
to operate the pinch roller before tape travel has
ceased, a brake will be instantly applied in such a
way as to cut or stretch the tape.
To eliminate the problem, this circuit allows the
reel motors to stop completely before the pinch
roller operation takes place when the PLAY mode
is effected from Fast Forward or Rewind.
2) During Fast Forward or Rewind TR18 is ON and
C24 is discharged through D46 > R74 > TR18.
At the same time, TR19 is OFF and TR20 is ON.
Consequently, TR20 collector connected 1С5
input terminal (5) is low level. When the PLAY
mode is effected from Fast Forward or Rewind,
TR18 is turned OFF and C24 is charged through
R71 and R73. During the charging time, TR19
base electric potential is low that it is in OFF
condition and TR20 is ON. On the other hand,
IC5 input terminal (6) becomes high level but
because the input terminal (5) is low level due to
TR20 ON, high level shows up at output terminal
(à). PLAY mode is therefore not effected.
When C24 is charged and ТК19 base electric
potential is increased to turn ТВІ9 ON, TR20
base electric potential is decreased to turn ТК20
OFF. Also, it results in a high level IC5 input ter-
minals ®© and ©. Therefore output terminals (4)
becomes low level to put PLAY. mode into effect.
In this manner, when the PLAY mode is effected
from Fast Forward or Rewind, Play Plunger does
not function while C24 is being charged.