Sharp VC-780E - Page 19

d.
Place
the
unit
to
the
playback
mode.
e.
Observe
the
waveform
of
the
PB
chroma,
and
push
the
(+
)or(-)
tracking
button
to
check
for
a
flat
PB
chroma.
This
adjustment
is
satis-
factory
if
a
flat
response
is
obtained
on
the
waveform
of
the
PB
chroma
when
the
(
+
)or(-)
tracking
button
is
pushed.
If
a
flat
response
cannot
be
obtained
roughly
adjust
the
guide
roller
using
the
special
bladed
screwdriver
until
the
PB
chroma
output
is
flat.
While
keeping
the
both(
+
)and(-)
tracking
buttons
down,
adjust
the
X-position
adjusting
nut
so
that
the
PB
CHROMA
envelope
becomes
almost
maximum.
In
the
case
of
rough
adjustment,
pay
particular
attention
to
the
outlet
side
(see
Fig.
1-24).
.
Adjust
the
retaining
guide
height
so
that
the
lower
flange
of
the
retaining
guide
touches
the
bottom
edge
of
the
tape.
At
that
time,
check
that
the
tape
is
not
curled
nor
wrinkled.
)
4.
The
A/C
head
height
and
azimuth
are
adjusted
after
rough
adjustment
of
the
tape
drive
train
has
been
done.
a.
Use
the
alignment
tape
and
play
back
its
audio
7kHz
signal
(monoscope
pattern
for
video
signaljand
observe
the
audio
output
on
an
oscilloscope.
.
Adjust
the
azimuth
adjusting
screw
so
as
to
obtain
the
maximum
audio
output.
_
Use the
alignment
tape
and
play
back
its
audio
1kHz
signal
(colour
bar
for
video
signal)
and
slowly
rotate
the
A/C
head
height
adjusting
nut
with
the
special
box
driver
so
as
to
obtain
the
maximum
audio
output.
After
the
height
adjustment,
use
the
alignment
tape
and
play
back
its
audio
7kHz
signal
(monoscope
pattern
for
video
signal)
again
and
adjust
the
azimuth
adjusting
screw
$0
as
to
obtain
the
maximun
audio
output.
After
this
adjustment,
apply
glyptal
to
the
screws
and
nuts
to
fix
them.
TP503 (GND}
5.
The
final
adjustments
of
tape
drive
train
and
X-
|
position
are
adjusted
after
adjustment
of
the
A/C
head
has
been
completed.
a.
Connect
the
oscilloscope
to
the
test
points
for
PB
chroma
output
(TP501)
and
head
switching
pulse
(TP502).
Allow
the
PB
CHROMA
signal
to
be
triggered
by
the
head
switching
pulse
of
TP502.
b.
Play
back
the
tape
drive
train
alignment
tape
(VROCPSV).
c.
Finely
adjust
the
guide
rolle’s
height,
observing
the
envelope
on
the
oscilloscope.
Push
the
(+)
or
{-)
tracking
button
while
adjusting
the
guide
roller,
in
order
to
obtain
an
envelope
waveform
which
is
as
flat
as
possible.
If
the
tape
is
above
or
below
the
helical
lead,
the
PB
chroma
waveform
will
take
the
shape
shown
in
Fig.
1-26.
Adjust
for
maximum
flatness
of
the
envelope
according
to
the
figure.
Note:
Adjustment
is
made
for
CH-1
of
switching
pulse
(low
level).
The
broken
lines
indicate
the
envelope
waveform
when
the
tape
does
not
run
properly.
Push
the
(+)
or
(-)
tracking
button
to
check
the
envelope
waveform.
After
adjustment,
tighten
the
setscrew
of
the
guide
roller
firmly.
Play
back
the
alignment
tape
(VROCPSV)
again
in
the
unloading
mode,
and
make
sure
that
there
is
on
change
in
the
PB
chroma
output.
POE
es
= : —: Head switching pulse
CH-2 CH-1 {TP502}
Figure 1-24.
TP502
(Head
switching
pulse}
TP501
(PB
chroma}
~/6 ee f- |
Figure 1-25.
19
a
S :
5
ere
|
|
a, a