Akai VS-2EGN

UNREG I9 V @
©
©
&
SERVO ©
Ics @D
X
3} ORUM HEATER
TRI
ou
| 4
TRB
RIS
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ie
=
TRO
O SRV 19 V (SERVO POWER SUPPLY)
m
Fig. 7-107 Servo Power Supply and Drum Heater Circuit
SERVO Servo Power Supply | _ Drum Heater
H OFF ON
L ON OFF
6-5-8 REEL PULSE, START SENSOR AND END SEN-
SOR DETECTION
When AL15V is supplied with the FUNCTION “ON”,
the lamp comes on, allowing detection of the start/end
sensor. In addition, the LED of the photo-interrupter
PH1 also comes on, allowing detection of the reel pulse.
For detection of the reel pulse, pulses generated by the
photo-interrupter are given a hysteresis in the compara-
tor for conversion to High (5V) and Low (OV). (Upper
Trip Point (UTP): SV) (Lower Trip Point (LTP): 3.4 V)
out
SCHMITT
REEL.P
NOTE: 12V is produced from SRV19V (19V) in the
servo PCB.
The reel pulse is used as the standard pulse for the reel
stop detection (See 6-6 “Syscon Error Detection’) and
tape counter.
Where the reel pulse is used as the tape counter, the
count is incremented or decremented by “+1” each time
the rising edge of the pulse is encountered twice. As the
detection wheel makes a complete revolution, 6 pulses
are generated and therefore the count is incremented or
decremented by “+3”,
1OL SV
UNREGISV AL I5V
START.S
Fig. 7-108 Reel pulse, Start Sensor and End Sensor Circuit
6-6 VS-2 SYSCON ERROR DETECTION
The VS-2 Syscon (micro-computer) provides error detec-
tion to ensure safe operation.
6-6-1 BREAKDOWN
In a mode where the loading motor runs, if either the
SW “A” or SW “B” state does not change within a cer-
Service Manual VS-2EGN
76
tain period of time, the motor is assumed not rotating;
all outputs are turned off and a key is no more accept-
ed. (This applies also to VS-5.) To recover from break-
down, first remove the cause of the loading error (for
Example, (a) improper cam position, @) disconnected
belt, (©) mech-drive circuit error, etc.) and then turn on
MAIN POWER at the rear.