Akai VS-2EGN

—_—
XK
6-6-2 REEL STOP
In a mode where the reel rotates (i.e., FF, REW, PLAY,
REC, CUE or REVIEW), if the rising edge of the reel
pulse is not encountered within a certain period of time,
the reel is assumed not rotating and the operation pro-
ceeds to the STOP mode.
The rising edge must O1s . FF/REW
be encountered at least 03s. . . CUE/REVW
once in: 13s. .. PLAY/REC
The revolution of the take-up reel is transmitted via
the belt and the pulse is generated by means of a photo-
interrupter.
Note that this applies only to the take-up reel; that is the
“supply” reel is not monitored.
6-6-3 DRUM STOP
In a mode in which the drum motor rotates (PAUSE to
PLAY), if the rising edge of SWP (switching pulse) is not
encountered at least once in 0.5 s, the drum is assumed.
not rotating, and the operation proceeds to the STOP
mode.
This also applies where SWP is not at the specified level
((; Carrere 2.0V ormore;sL........ 0.8V or less)
even though the drum is revolving,
6-6-4 DETECTION OF LAMP FAILURE (ITS OMIS-
SION)
INI
LAMP.
JU
i
I
PHOTO |
COUPLER |
Fig. 7-109 Reel pulse Generation Circuit
Lamp failure needs to be detected when the tape is run-
ning, during which time the reel pulse is always detect-
ed.
Lamp failure brings a problem only when the tape is
pulled excessively near its end or when it broken while
it is running.
Detection of the reel pulse involves a delay in each
mode. Therefore, in the event of lamp failure, this delay
causes the tape to be pulled near its end. This pull is
about 500g (based on calculation), while the tape is de-
signed to withstand a pull of 3 kg. This, together with
the fact that lamp failure rarely occurs, makes it possible
to omit the operation that is concerned with detection
of lamp failure.
As shown in Fig. 7-109, the lamp is connected in series
with LED used for reel pulse detection, and thus the reel
pulse is cut off in the event of lamp failure.
Service Manual VS-2EGN
7. AUDIO/VIDEO PRE-AMP CIRCUIT
7-1 AUDIO CIRCUIT
7-1-1 RECORDING SYSTEM
Audio
signals
from
the
built-in
tuner
or
from
the
line
in-
put
are
supplied
to
the
connector
PS
pin
©®.
When
a
DIN
connecter
is
connected,
the
line
takes
preference.
The
input
level
of
the
audio
input
signal
is
adjusted
at
the
Automatic
Level
Control
(ALC),
the
DC
compo-
nent
is
removed
by
Cl,
and
the
rest
is
fed
to
IC1
(BA
5102)
pin
®.
The
signal
is
amplified
at
the
AMP
by
about
37
dB,
output
to
pin
@via
the
electronic
switch
SW1,
enters
pin
©.
passes
through
electronic
switch
SW2,
is
amplified
by
about
30
dB
at
the
line
amplifier,
and
output
to
pin
The
output
at
pin
is
divided
as
follows:
1) The output is subjected to negative feedback to the
line amp from pin@ via C3,
2) The signal has its component removed by C20, is
rectified by D1, smoothed by C24 and fed to ALC bet-
ween pin () and pin (wy) to provide level control.
3) The signal is fed to AUDIO OUT of connector P5
pin@)as an EE output via C18.
4) In parallel with this, the signal is subjected to the
level adjustment at VR3 (REC LEVEL), fed to IC1 pin
@, and supplied to the REC AMP.
The REC AMP performs peaking by means of R16, L3,
and C17, to compensate for the loss of high frequency
components during recording/and playback of magnetic
tape, so as to supply constant recording current to the
head regardless of the signal frequency, and the bias cur-
rent is supplied to the head. The DC component is re-
moved by C22.
7-1-2 PLAYBACK SYSTEM
The signal reproduced from the tape by the audio head
is fed to connector P3 pin), fed to IC1 pin), passes
through EQ AMP, and SWI, and is output to pin @).
This signal is subjected to level adjustment at VR2 (PB
LEVEL), fed to pin ®, passes through SW2 and LINE
AMP, is output to pin (@, ‘and passes through C18.
One output is supplied to LINE OUT as AUDIO OUT,
and the other is fed to the RF converter.
77