Akai GXC-750

28
OPERATION DURING FAST FORWARD
(Refer to Fig. 43)
1) At F.FWD mode, when the tape counter scale
reaches “900”, the contact point inside the tape
counter makes contact and point a) voltage
becomes zero.
2) Therefore, transistor TR2 is turned OFF, TR2
collector voltage increases and at the same time
a charge current begins to flow to condenser C4
through resistor R20.
3) The charge to condenser C4 is of extremely short
durations.
4) At F.FWD, when the tape advances to “000”, the
contact point inside the tape counter mementarily
separates.
5) At the same time that the contact point releases,
a charge current begins to flow to condenser C3.
6) After a short period of time when charging is
completed point (a) voltage becomes high, bias
is supplied to the base of transistor TR2, and
TR2 is turned ON.
7) When TR2 is turned ON, the electric charge
(charged at condenser C4 while TR2 was turned
OFF) passes resistor R23 from TR2 and discharge
begins.
8) Consequently, point (b) electrical potential be-
comes largely minus and the anode side of diode
D3 is minus biased.
9) Therefore, transistor TR3 is turned OFF and stop
plunger solenoid SL1 operates and the deck
enters STOP mode in the same way as explained in
Section VIII, Item 1, 1).
5. SYSCON MALFUNCTION PREVENTION
CIRCUIT (Refer to Fig. 44)
This circuit is for preventing syscon malfunction
when the power switch is turned on or the machine
set to FWD or REV from stop mode.
SYSCON MALFUNCTION PREVENTION WHEN
POWER SWITCH IS TURNED ON
1) When the Power Switch is turned ON, power is
supplied to the syscon circuit. However, the
various transistors inside the syscon must be
maintained at a stabilized condition as shown
in Fig. 44.
2) Therefore, the moment the Power Switch is
turned ON, current passes diode D2 and flows to
TR3 through resistor R7, resistor R15 and diode
D3 and TR3 is turned ON.
3) Because TR6 assumes an OFF condition due to
TR3 having begin turned ON, TR5 is stabilized
at ON, and TR6, and TR7 at OFF condition.
SYSCON MALFUNCTION PREVENTION WHEN
DECK ENTERS REV OR FWD FROM STOP MODE
1) Once power is supplied, the syscon assumes a
stabilized condition as described above. However,
as shown in Fig. 42, because play switch SW12
separates when the Fwd Button is depressed,
syscon circuit operation becomes unstable.
2) Therefore, when tape travel begins, transistor TR1
is momentarily turned ON by micro switch SW15
until bias is supplied to the base of transistor TR3,
bias is supplied to TR3, and the syscon circuit is
‘maintained at a stabilized condition.