JVC KD-A66 Service Manual

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Fig. 11
Microcomputer
In the KD-A66, the tuning function is controlled by
the 42-pin LSI microcomputer which stores instructions
of about 2000 steps and processes normal instructions
at 10 msec. The connection diagram is shown in Fig.
11. In addition, its incorporated timer controls the
timing of the entire deck. The process is performed in
the P-channel MOSFET and the output is used in the
form of an open drain type pull-down.
The clock circuit stably operates because it consists of
an LC resonance circuit. Since the microcomputer is
provided with an interruption function, the pulse from
the tape counter is counted with interruption.
Auto-stop
The rotation pulse signal from the Hall IC is waveform
rectified and differentiated at its leading and trailing
edges. Then, the monostabie multiple circuit generates
a pulse of about 20 msec which is in turn applied to
the interrupt terminal INT of the microcomputer.
The microcomputer detects the tape position by the
rotation pulse signal and also generates an auto-stop
signal if no signal is applied for 1.5 sec or more.
Auto-rewind circuit
In the KD-A66, when an auto-stop signal is emitted
from the microcomputer (ICKOI) at the tape end
during playback or record, the tape is automatically re-
wound to the beginning and the deck enters the PLAY
or STOP mode by switching the MEMORY switch
(SW55)}.
KD-A66A/B/C/E/J/U
If the tape counter displays “999” halfway, since the
deck also enters the PLAY or STOP mode, the data in
the tape can be repeatedly reproduced between “‘0°’
and ‘‘999’’. To describe this operation, the MEMORY
switch (SW55) is set in the PLAY mode. AT first, when
an auto-stop signal is emitted from the microcomputer
at the tape end during playback, transistor XKO6 goes
on, thus lowering the voltage at the auto termina! (pin
5) of mechanism contro! 1C51. At this time, the auto-
rewind instruction is emitted from 1C51.
When the tape is rewound to the beginning by this
instruction, the auto-stop instruction is emitted from
pin 12 of the microcomputer. Likewise, when the volt-
age at the AUTO terminal (pin 5) of I1C51 is lowered,
the PLAY instruction is automatically emitted from
the microcomputer.
Next, to describe this operation, the MEMORY switch
is set in the STOP mode, At first, when an auto-stop
signal is emitted from the microcomputer at the tape
end during playback, transistor XKO6 goes on, thus
lowering the voltage at the said AUTO terminal. At this
time, the auto-rewind instruction is emitted from 1051.
When the tape is rewound to the beginning by this
instruction, the auto-stop instruction is emitted from
pin 12 of the microcomputer. However, since the base
voltage of tansistor X63 is kept to about 1V during the
REW instruciton, the emitter voltage of transistor X63
is lowered to 0.2V when transistor XKO6 goes on. At
the same time, transistor X63 goes on and functions to
pull the STOP terminal (pin 1) of 1C51, thus entering
the deck into the STOP mode.
In addition, with the MEMORY switch in the OFF
state, the auto-stop signal from the microcomputer,
when transistor XKO6 goes on, passes across diode D63
and also functions to pull the STOP terminal (pin 1) of
1C51, thus entering the deck into the STOP mode.
Since the MEMORY STOP/PLAY function can be per-
formed even during the auto-rewind operation by the
auto-rewind circuit, the data in the tape can be re-
peatedly reproduced between ‘999” in the tape
counter and the tape end.
XKO6 4 [_ VMwis37-001v |
STOP] R38
No. 4193

JVC KD-A66 Specifications

General

Brand	JVC
Model	KD-A66
Category	Cassette Player
Language	English