Tape Transport Section; Systemcontro] Ls] - Teac C-1 Service Manual

TAPE TRANSPORT SECTION
The system control section of C-1 employs an LSI (large
scale integrated circuit).
This section also features several newly developed circuits
to maximize the performance of the dual captsan system.
Specifically, the tape loading circuit which automatically
pulls in the slack of a tape when a cassette is loaded, the
tape speed control circuit to run the tape at a constant
speed in the fast forward mode, the electromagnetic reel
1. SYSTEM CONTROL LSI
1-1 INTRODUCTION
The system control section of C-1 employs a 24-pin dual in
line P-channel MOS LSI. This LSI is specially designed asa
system control circuit on the basis of studies made of the
functions of many conventional tape decks. The block
diagram of the LSI is shown in Fig. 1.
The LSI includes an input priority circuit, an operational
memory, a timing control circuit, etc.
The LSI is operated by one +10V to +16V DC power
supply. All operations of the LSI are synchronized by an
external clock signal. Functions of the LSI cover almost all
controls of the tape deck including REC, REC MUTE, REC
SAFE, STOP, STAND-BY (PAUSE), REVERSE, F. FWD,
RES
STI
RCI
RSI
RMI
SBI
PYI nom
EFT DECODER
RWI
RVW
MN4
R/M2
MOD
motor brake circuit, and so on.
Features and operation of the tape transport section are
described in this manual. Voltage values, waveforms, delay
times and other values used in the description are for your
reference, and may change depending on the parts used,
power supply voltage and other factors.
Unless otherwise specified, the initial state referred to in
the description means the STOP mode.
REWIND, REVIEW (CUE), RESET and WAIT.
Tape deck controls will be different in different models
even if the same LSI is used. Therefore, connections and
input/output combination must be changed in different
models.
Unused functions in the C-1 are omitted from this descrip-
tion. Both input and output of the LSI use HIGH=TRUE
for the C-1. That is, the command signal for a given opera-
tion is input at the high level, and the output signal from
the LSI necessary for that operation is also at the high level.
All outputs are open drain and thus all terminals in use
must be grounded to VDD (GND) by means of a resistor.
The LSI is refered to as the SYS-CON in the following
paragraphs.
Vss(+B)
Vpo(OV)
= SI(CLOCK)
i
~wW
a
oF}
2
RMO
RCO
PYO
SBO
R/BK
OUTPUT FFO
DECODER RWO
BUFFER WT
STATES MEMORYS
T- 1289
Fig. 1 LSI Block Diagram