Sharp VT-3428X Service Manual page 32

Head switching pulse (TP202)
Figure l-40.
Connect an oscilloscope to the audio output
terminal.
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
on an oscilloscope. (See Figure 1-41.)
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.
Perform the adjustment in b) again.
After this adjustment, apply glyptal to the
screws and nuts to fix them.
When the tape is above the helical lead.
Supply side
.
Supply side guide
roller rotated in
clockwise direction
(lowers guide roller) to
Adjustment
flatten envelope.
8 Adjustment of tape (VROUBZFS) drive train and
.
X-Position.
Connect the oscilloscope to the test points
Set the synchronism of the oscilloscope to EXT.
The PB CHROMA signal is to be triggered by
the head switching pulse (TP2204).
Play back the tape drive train alignment tape.
Push the (+) or (-) button to change the
envelope waveform from MAX to MIN, and
on the supply and take-up sides with an
adjusting screw driver, to obtain an envelop
waveform that 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 Figure l-43.
Adjust for maximum flatness of the envelope
as the step 6, e) in page 31.
When the tape is below the helical lead.
Take-up side
Supply side guide
Take-up side guide
roller rotated in
roller rotated in
counterclockwise
clockwise direction
direction (raises guide
(lowers guide roller) to
roller) to make the
flatten envelope.
tape float above the
helical lead. The supply
side guide roller is
then rotated in the
clockwise direction to
flatten the envelope.
Figure l-43.
Azimuth adjusting
screw
Figure l-42.
Figure l-41.
Supply side Take-up side
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.
Box driver
A/C head height
adjusting screw
nut