Toshiba D-VR3SU Service Manual page 116

Circuit Operating Descriptions
(2) Mechanism/Circuit Control
When the u-COM inputs operator's commands via the key input or remote input, the mechanism and circuits are
set to the command mode. This function controls mechanism/servo section and audio/video processing section.
1) Cassette Loading Control
Controls loading and ejection of a cassette and determines the mechanism operation mode; tape loading/
unloading, action/release of various breaks, tension, take up mechanism etc.
2) Tape Protection Sensor Monitoring
Detects abnormal operation in tape using the supply and take up end sensor, reel sensor and SW 30Hz pulse
for drum rotation.
3) Capstan Motor Control
Determines the tape speed and direction, fast forwards and rewinds the tape etc.
4) Tape Counter Control
Counts the control pulses on the control track, picked up by the control head and shows it on the digital
multidisplay.
5) Servo Control
Determines the operation mode of the servo circuit. Control the speed of drum and capstan motor, and then
Control the phase of drum and capstan motor.
6) Record Safety Tap Detection
Detects the safety tab on the rear of a cassette to prevent a prerecorded program from being erased.
7) Loading/Unloading control
Controls a series of loading/unloading operation after the u-COM judges the operation mode and sets the
mechanism to suitable mode. Fig. 7-13 show correlation between u-COM and peripheral components during
the loading/unloading operation.
The mechanism state switch (PROG. SW) detects the mechanism position. When the driving gear is turned by
the loading motor, the switch driving slider traces the groove, and this switch stops at the correct position
corresponding to each mode. In other words, the u-COM judges the present mechanism state from the PROG
SW after receiving the mode data, then it outputs the loading motor and capstan motor control signals.
This continues until the PROG SW reaches the correct state by the u-COM.
FUNCTION-TIMER
OPERATION
MODE
DISPLAY
AND
KEY
MATRIX
CAPSTAN / DRUM
7-16
DFG,DFG
CFG
MOTOR
Fig. 7-13 The Relationship Between u-COM, Capstan, Cylinder and Loading Motor
MECHANISM STATE
INFORMATION
<u-COM>
SYSTEM
CONTROL/
OSD
SERVO BLOCK
LOADING
CAPSTAN
MOTOR
MOTOR ASS'Y
(3 in 1)
PROG
SW
LOADING
GEAR