Akai VS-2EGN

7-2, VIDEO PRE-AMP CIRCUIT
7-2-1 RECORDING SYSTEM
The recording signal consisting of a mixture of the FM
signal from video PCB and the low band converted
colour signal, is fed to connector P1 pin ©. This re-
cording signal passes through the emitter follower (EF)
of TRIO, and is fed to REC AMP (TR8, TR9) (Audio/
Pre PC Board) . This REC AMP operates to optimize
the recording current for all signal frequencies.
The recording signal is fed to the video heads 1 and 2,
and recorded on the tape.
7-2-2 PLAYBACK SYSTEM
PB signals from the video heads 1 and 2 are fed to IC2
(AN6320N) pins) and (5) respectively on the Audio/
Pre PC Board, and then amplified at the 1st AMP.
Signals at the video heads 1 and 2 are extracted by the
Switching Pulse supplied to pin ®, and output from
pins ® and(9) repsectively.
Then, the signals are fed to pin (1), made into a con-
tinuous signal by the MIX AMP, and output to pin @.
Then, the signal is passes through the EF TR7, and sup-
plied to the video PCB through connector P1 pin 6)
(PRE-OUT).
1) Switching operation
OVERLAP NOISE
a Le
CH-I SIGNAL
CH-2 SIGNAL fame
ORUM FF
‘SIGNAL
CH-I SW
OUTPUT
CH- 2 SW
OUTPUT | LH
CONTINUOUS
SIGNAL
Fig. 7-112 Switching Operation
PB signals from the video heads 1 and 2 alternate every
180° of the 25 Hz switching pulse.
The times during which there is no PB signal contain
noise, and so the channels are overlapped to avoid gaps
in picture reproduction. Accordingly, Video heads 1
and 2 cannot be mixed simply. For this reason, the PB
signals are switched by the 25 Hz drum flip-flop to fom
a continuous PB signal. Refer to Fig. 7-112.
‘Service Manual VS-2EGN ——————_—