Sharp VC-90ET - Page 25

PB CHROMA envelope (TPS01)
Oa
|
|
h
|
I
Head
switching
pulse
(TP502)
Figure 1-58.
6.
Adjustment
of
A/C
head
height
and
azimuth
a)
Connect
an
oscilloscope
to
the
audio
output
terminal.
b)
Use
the
alignment
tape
and
play
back
its
audio
6
kHz
signal
(monoscope
pattern
for
video
signal).
Adjust
the
azimuth
adjusting
screw
to
obtain
the
maximum
audio
output
onan
oscilloscope.
(See
Figure
1-59.)
c)
Use
the
alignment
tape
and
play
back
its
audio
1
kHz
signal
(colour
bar
for
video
signal)
and
slowly
rotate
the
A/C
head
height
adjusting
nut
with
the
special
box
driver
to
obtain
the
maximum
audio
output.
d)
Perform
the
adjustment
in
b)
again.
e)
After
this
adjustment,
apply
glyptal
to
the
screws
and
nuts
to
fix
them.
Supply side guide
roller rotated in
clockwise direction
(lowers guide roller) to
flatten envelope.
Take-up side guide
roller rotated in
clockwise direction
flatten envelope.
When
the
tape
is
above
the
helical
lead.
a
Supply
side
Take-up
side
4,
(lowers guide roller) to
VC-90ET
Box driver
Azimuth
adjusting
AIC
head
height
screw
adjusting
screw
nut
Figure
1-59.
Figure
1-60.
7.
Adjustment
of
tape
drive
train
and
X-Position.
a)
Connect
the
oscilloscope
to
the
test
points
(TP501)
for
PB
CHROMA
envelope
output.
Set
the
synchronism
of
the
oscilloscope
to
EXT.
The
PB
CHROMA
signal
is
to
be
triggered
by
the
head
switching
pulse
(TP502).
b)
Play
back
the
tape
drive
train
alignment
tape.
C)
Push
the
(+)
or
(-)
button
to
change
the
envelope
waveform
from
MAX
to
MIN,
and
MIN
to
MAX.
Adjust
the
guide
roller’s
height
on
the
supply
and
take-up
sides
with
an
adjusting
screw
driver,
to
obtain
an
envelop
waveform
that
is
as
flat
as
possible.
—
d)
If
the
tape
is
above
or
below
the
helical
lead,
the
PB
CHROMA
waveform
will
take
the
shape
shown
in
Figure
1-61.
e)
Adjust
for
maximum
flatness
of
the
envelope
as
the
step
5,
e)
in
page
24.
When the tape is below the helical lead.
Supply side Take-up side
; —é
- N
7
x
~~
.
x
Supply side guide
roller rotated in
counterclockwise
direction (raises guide
roller) to make the
tape float above the
helical lead. The supply
side guide roller is
then rotated in the
clockwise direction to
flatten the envelope.
Take-up side guide
roller rotated in
counterclockwise
direction (raises guide
roller) to make the
tape float above the
helical lead.
The take-up side guide
roller is then rotated in
the clockwise direction
to flatten the
envelope.
Figure 1-61.
“25