Sharp VL-C780S Serviceanleitung Seite 176

VL-C780S/H/X
VL-C7400E
VL-C690S/H/X
VL-CG400E
2-4. Head amplifier circuit .
Also when V-REC signal is "L", pin (26) of 1C301 becomes "H", and turns on SW9-12, disallowing a record sig-
nal to flow in any head and setting REC PAUSE status. This model is equipped with a rotary erase head, which
erases a recorded signal in place of the conventional juli erase head. in this operation, the ROT ERASE signal
from the system controller (1C801) turns on Q3303, and actuates the oscillation circuit consisting of Q3302,
Q3301, etc. The oscillation frequency is a resonance frequency of combined capacitance of L3302 and C3304-
C3306, approx. 8.8 MHz. Then it is reformed and amplified by C3308 and inductance of the rotary transform-
er, allowing an erase signal to flow in the rotary erase head.
Then, in the playback mode, PB5V is supplied to the video head turning on $W1-4, and the rotary transformer
is setin the playback mode. In playback mode, the above SW1- 4 pulses have their polarity inverted. Therefore
when video head R1 (CH1) playback a signal from a tape, SW-1 puise is "H", then inverted in the inverter to
become "L", which open SW5, transmitting a signal from a head to PB1 pre-amplifier.
The output from PB1 pre-amplifier is supplied to SW15 via SW13 transmits the output from PB1 pre-amplifier
to SW15 while H-SW-P signal is "H". SW15 outputs the above input when H-AMP-SW signal is "H". The signal
outputted from SW15 is supplied to PB5, amplified by 10dB, then outputted from pin (41) of 1C301.
Playback output conditions
i
OC (
GG
A a a
SC i
2-5. Flow of record C-signal
The C-signal outputted from the camera part is supplied to pin (1) of connector BG. It is first inputted in pin
(16) of 1C501, the record character part being damped by use of a switch. Then it is outputted from pin (1). The
signal is divided into two, one of which becomes EE signal and the other a record signal the same as Y-signal.
The EE C signal is level-adjusted in a resistive divider, inputted in pin (5) of 1€2201, and supplied to 12dB AMP
via the record and playback switch in the IC. The output is mixed with said Y-signal in the IC, outputted from
pin (10) through the video amplifier to become EE video output signal.