Sansui FR D55 Service Manual

Page 2

1. OPERATION

The FR-DSS is a computerized full automatic music selection turn-
table in which a mechanism that can automatically select any music
on a record disc at random.

Refer to XR-Qli SERVICE MANUAL, for basic operations which
are almost equal to this model.

The control circuits for FR-DSS can mainly be divided into a servo
circuit to control a DD motor and a microcomputer and its peri-
pheral circuit to mainly control a tonearm.

Refer to FR-D45 SERVICE MANUAL, for operation of the servo
circuit, since the operation is entirely the same as in the FR-D45.

1-1. Basic circuit configuration for full automatic
operation (See Block Diagram on Page 2.)

A. Microcomputer

The microcomputer uPDS46C-181 controls the operations of the
tone arm, lifter, and DD motor in such a way that every control sig~
nal is output to the corresponding output port after each of signals
applied to the input ports has been executed in accordance with a
program stored in the microcomputer memory.

The microcomputer becomes enable only when the output ports are
at H level in potential; in other words, every circuit connected to
pins (at H level) of the microcomputer operates.

B. Input peripheral circuits for the microcomputer

1. Control switches

These are manual operation switches to perform the full automatic
operation. Since the control switches are dynamic-connected to the
ports of the microcomputer, if a control switch is pushed, two
Input/output pins are connected to each other in the microcomputer
and thereby the microcomputer begins to operate. (See Block Dia-
gram.)

2. A sensor and the sensor circuit

In operation with the B sensor, the A sensor detects the tonearm
positions necessary for automatic operation. In other words, the A
sensor detects the lead-in position of a 30cm- or I7cm~size record
disc and also detects whether the tonearm rests on the arm rest (A
x B=I)ornot(AxBa¢ 1).

The tonearm positions (A x B = I and A x B 55 1) have the following
relations to the start/step switch:

0 If START/STOP switch is set to start (The turntable is
at a stop)

. . Lifter Operation of Aummatie
Am 5" Position Turntable Operation
0n the rest Up [D = 1) Rotates after In-operation
(A X 3 = 1) ZOOms
Same as above Down (C ,= I) ln-operation after
D = 1 in CW
0" the record disc Up (D E 1) Immediately To C = I in CW

IA x B a! 1) rotates

Same as above Down (C = 1)

o If START/STOP switch is set to stop (The turntable is in
motion and also in automatic operation.)

. . Lifter our on of Automatic

Am "mm Position Turntable Operation
On the rest Up (D = 1) Immediately
(A x B = 1) rotates
Same as above Down (C x I)
On the record disc Up (D = 1) Stops at point Arm return
(A X E ii 1) AB
Same as above Down (C = 1) Arm return

0 If START/STOP switch is set to stop (The turntable is in
motion and also in automatic operation.)

. . . Operation of
Ann Motion Status Automatic Operation Turntable
During up motion Out of automatic operation Immediately stops
(AxB=1) atD=l)
During up motion Arm return after D a I Immediame stops
(AxB# 1) atpointAE
During horizontal Immediately out of automatic Immediately stop:

motion (A x B =1) operaimn »

During horizontal Arm return in CCW ->CW

Stops at point
motion (AXE? I) or in CCW AE

During down Arm return after D = 1 Same as above
motion (A x B #1)

During return Disable

motion

Note: In the above lists, A x B =1, D =1, and C =1 mean the states
in which the sensors B,C, and D are detecting the correspond-
ing signals, respectively, on the timing chart. CW means that
the micromotor rotates clockwise; CCW means that the
micromotor rotates counterclockwise. Refer to the respective
sections for operations of the sensors A, B, C, D and the
mlcromotor.

The signal detected by A sensor is applied to the input terminal 33

of the microcomputer through flcmb and flcm c.

3. B sensor and the sensor circuit

In cooperation with the A sensor, the B sensor detects the tonearm
position and the end detection signal in the record lead-out groove
after finishing over play.

The signal detected by the 8 sensor is applied to the input terminal
34 of the microcomputer through transistor 2;, and med.

4. C sensor, D sensor and the sensor circuits

The C and D sensors comprise a lifter cam and the micro-switches,
respectively. The C sensor detects the down-position of the lifter;
the D sensor detects the up-position of the lifter.

In the both sensors, the terminal 2 of each micro-switch is shorted
to the ground whenever the lifter states are detected.

5. E sensor and F sensor

The E and F sensors mounted within the head shell feed into the
microcomputer the signals necessary for automatic disc slze selec-
tion and automatic music selection. In other words, in order to
implement complex full automatic operations, both the sensor sig-
nals are fed into the computer after being discriminated into E2, E3,
F1, and F2, respectively, through appropriate circuits.

The arrangement of the E and F sensors is shown in Fig. H, and E
sensor ls called a leading sensor because E sensor first detects the
signal.

n