Toshiba D-VR3SU Service Manual page 121

(17) Trouble Detection
The trouble detection circuits are provided to protect the from damage (Fig. 7-15). The reel lock sensor detects
incorrect rotation of supply and take up reel. The reel lock sensor consists of the disk and photo sensor installed at
the bottom of the reel disk. the disk has 6 or 8 shielder parts and the photo sensor consists of the LED and photo
transistor assembly. When the light is shielded by the the shielder or enters the photo transistor, the output is
obtained from the photo sensor. IC601 measures the period of the pulse. When it is 4 seconds or more during
record/play, the VCR enters the reel emergency mode.
The VCR maintains the unload-power-on state in the reel emergency.
(18) Cylinder Lock Sensor
If the frequency of D-FG is less than 230Hz or more than 430Hz during 500msec, and such stuation occurs 3 times
contined, micom makes the VCR drum emergency.
(19) Tape End Sensor
When end sensor detects the transparent section at the end of tape, the VCR enters auto rewind mode, except
during timer recording and OTR mode. The cassette LED emits light through the transparent section of tape to
the photo transistors, which are installed at both ends of the cassette. When start sensor detects the start section
of the tape during reverse search and rewind, the VCR automatically goes to stop mode.
R607
R605
C602
R603
R604
R602
Fig. 7-15 Reel and Cylinder Lock T.END/S.END Sensor
R606
65
82
2
1
R601
Circuit Operating Descriptions
7-21