Epson PX-8 Technical Manual page 155

REV.-A
3.1.6 Mechanism Control
3.1.6.1 Tape Count Detection
Tape count detection is accomplished by mirrors directly coupled to the left reel (the reel taking
up tape during read/write) and a photo-reflector assembly (a single element which is a combina-
tion of a light emission diode and a phototransistor). Fig. 3-11 shows the circuit and the position-
al relationship between the elements.
Light emission
diode Phototransistor
VBSB
R7
I50K
,.-----.,
,~---,
2
1 3 4
R41
4.7K
r-
------1
FTI
NJL
5141E
I
Photo-reflector
I
~~------------------~I
I
I
07
MAI53
L
---'t-- --
R8
100
G N 0 0------+-------__ -
CNTR -----......
Mirror _ _
Ie 5 2164069
Fig.3-11 Tape Count Detector Circuit and Positional
Relationship between Elements
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1/
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The reflector drum has four mirrors on it as shown in Fig. 3-11. One reel revolution is counted as
four.
3.1.6.2 Head Pinch Motor Control
The head pinch motor moves the P-Iever assembly consisting of the pinch roller and the read/
write head. The assembly slides back and forth to accomplish tape loading and unloading. This
motor always revolves in a direction and drives two cams; one is used to move the P-Iever assem-
bly back and forth and the other makes and breaks thc HSW switch, which detects the read/write
head position. Fig. 3-12 shows the control circuit.
3-9
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