Sharp VC-MH80 Service Manual page 24

VC-MH80
PB CHROMAenvelope (TP2201)
Head switching pulse (TP2202)
7. Adjustment of AIC 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
on an oscilloscope. (See Figure 4-39.)
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 adjust-
ing 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.
When the tape is above the helical lead.
Adjustment
CH-2
,
Supply side
Take-up side guide
Supply side guide
roller rotated in
roller rotated in
clockwise direction clockwise direction
(lowers guide roller) to (lowers guide roller) to
flatten envelope. flatten envelope.
8. Adjustment of tape drive train and X-Position.
a) Connect the oscilloscope to the test points
(TP2201) 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 (TP2202).
b) Play back the tape drive train alignment tape.
c) Push the (+) or (-) button to change the enve-
lope 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.
the PB CHROMA waveform will take the shape
shown in Figure 4-41.
e) Adjust for maximum flatness of the envelope
as the step 6, e) in page 23.
When the tape is below the helical lead.
Take-up side
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.
24
Azimuth
screw
Supply side Take-up side
Take-up side guide
roller rotated in
counterclockwise
direction
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
adjusting screw
nut
(raisesguide