Sharp VC-90ET - Page 37

5. Observe the video output terminal voltage
(across the terminal resistor) on the oscilloscope
screen. If the playback video signal level is
above 1.0Vp-p, turn R228(deviation control)
clockwise.
If below 1.0Vp-p, turn the control counter-
clockwise. Now make self-recording and
playback again.
6. Repeat the above stap5 to finally get the
playback video signal level at 1.04 0.04Vp-p, as
shown in Figure-2-9.
Measuring
instrument
Oscilloscope
Standard colour bar
(stair-case waveform)
TP301 (GND at TP302)
External trigger
(video output terminal)
Adjusting R321 | R320 |
point (recording Y (recording
control) chroma control)
Red level
Specifica- Sync tip level
‘ Y F 23 + 1mVp-p
tion 84+ 4mVp-p
Note:
TP301 and TP302 are located on the head amp
PWB.
1. Place the unit to the record mode.
2. Feed the colour bar signal to the video input
terminal.
3. Observing the waveform on the oscilloscope
screen (external trigger at video output
terminal), take the following staps.
a) Connect the oscilloscope’s ground and signal
leads to TP302 and TP301, respectively.
b) Turn R321 (recording Y control) to minimum.
¢) Adjust R320 (recording chroma control) so
that the red level be 23 + 1mVp-p as shown in
Figure2-11.
4. Adjust R321 (recording Y control) so that the
sync tip be 84 + 4mVp-p as shown in Figure2-12.
37
VC-S0ET
23+1mVp-p
10mVidiv
10psecidiv
Figure 2-11.
z=
=.
Es ae
a
HI
Sel ls 50mVidiv
=
_]
:
10psecidiv
Figure 2-12.
m ADJUSTMENT OF Y/C PLAYBACK
CIRCUIT
Adjustment of playback video signal level
Oscilloscope
Playback
Alignment tape (VROCPSV)
(stair-case waveform)
Test point Video output terminal
Adjusting point | R209 (playback level control)
Specification 2.0 £0.1Vp-p (not terminated)
1.
Insert
the
alignment
tape
and
place
the
unit
to
the
playback
mode.
2.
Hook
up
the
oscilloscope
to
video
output
terminal.
Adjust
R209
(playback
level
control)
so
that
the
on-screen
waveform
be
2.0
+
0.1Vp-
p
as
shown
in
Figure2-13.
Measuring
instrument
Tape used