Sharp VT-3418X, Service Manual, Page: 35 / 170

envelope
Head switching pulse
Figure
Adjustment of A/C head height and azimuth
a) Connect an oscilloscope to the audio output.
(Pin of EL connector)
Use the alignment tape and play back its
audio 7 signal (monoscope pattern for
video signal). Adjust the azimuth adjusting
screw to obtain the maximum audio output
on an oscilloscope. (See Figure
Use the alignment tape and play back its
audio 1 signal 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 again.
After this adjustment, apply to the
screws and nuts to fix them.
Azimuth adjusting
screw
Figure
Figure
Adjustment of tape drive train and X-Position.
a) Connect the oscilloscope to the test points
for envelope output.
Set the synchronism of the oscilloscope to EXT.
The
signal is to be triggered by
the head switching pulse
Play back the tape drive train alignment tape.
Push the or button to change the
envelope waveform from MAX to and
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.
If the tape is above or below the helical lead,
the waveform will take the shape
shown in Figure
Adjust for maximum flatness of the envelope
the step in page
When the tape is above the helical lead.
When the tape is below the helical lead.
Supply side
Take-up side Supply side Take-up side
Supply side guide Take-up side guide
Supply side guide
Take-up side guide
roller rotated in roller rotated in
roller rotated in
roller rotated in
clockwise direction clockwise direction
counterclockwise
counterclockwise
direction (raises guide
Adjustment
(lowers guide roller) to (lowers guide roller) to
direction (raises guide
roller) to make the
flatten envelope. flatten envelope.
roller) to make the
tape float above the
tape float above the
helical lead. The supply
helical lead.
side guide roller is
The take-up side guide
roller is then rotated in
then rotated in the the clockwise direction
clockwise direction to
to flatten the
flatten the envelope.
envelope.
Figure