Tascam 122 Service Manual page 19

PINCH ROLLER
T R6 57
r--'
I ,
,
I
I
I
,
I
I
C6 1 1 '
I , I
"659
t
122
Fig. 3-15 Tape-end detect circuit
19
Iy. When 0607 is off, capacitor C61 0 is charged
by current flowing via path
® .
When 0607 is
on, C610 discharges via path
® .
Since the time
constant of C610 and R631 is much smaller
than that of C610 and R656 (or R657), the
charging of C610 proceeds slowly while it dis­
charges rapid Iy . As a resu It, the voltage at
'liJ
remains below +1.5 V while 0607 is repeatedly
turned on and off.
When the tape reaches its end and stops running,
the counter pulley and the ring magnet stop
rotating. At this time, the reed switch stops
operating in either its on or off position depend­
ing on where the ring magnet has stopped. If
the reed switch is on, the base current of 0607
stops flowing turning it off, and current flowing
along path
®
starts to charge C610 as soon as
U601
P LAY 1 2 R6 11
OUT
FAST 1 4 0 6 10
I
STOP
I
OUT
"6 06 2 STO P
F
' N
IN L693
C60 6 L _4_ME_MO _ _ _ _
w..._ _ _ _ _
SO_L_EN_O_'D-,
"6 62
Q613
cu rrent from path
®
completes charging C609.
If the reed switch is off, 0607 is already off be­
cause the reed switch has turned off and, there­
fore, current from path
®
continues to charge
C610.
When the voltage across C610 (voltage at
® )
exceeds approximately 3 V, base current flows
through transistor 0513 via path
(J),
thereby
turning on 0613. 0613 turns on approximately
2.3 seconds
aher
0607 turns off. Since 0613
turning on is equivalent to depressing the
stop button, the deck enters the stop mode.
When the deck enters the stop mode, current on
path
CD
or
(?)
stops flowing and C610 dis ­
charges via R656 and the fast solenoid and via
R657 and the pinch roller solenoid (current
flows in the direction opposite to
® ).
r - - - - - - - - - - - - - r - - - - -
+3 9"
r-----------
I
f---,--~- +
13"
CD @
r---.-----j _____ )
FLASHING
CIRCUIT
FLASHING
CIRCUIT
CD@
" 656
FAST
SOLENOID
C69 3
0 693
0695
T
L 691
A
REED
SWITCH
S693
---"'II
0607
+
R634
®
C609
:
@®