Sharp VC-780E Service Manual page 31

vy
ee oe
Video output terminal
Adjusting point R201 (EE level control)
Note:
with a 75-ohm impedance.
1. Set the unit to the record mode.
Fig. 2-1 2.
1.0 Vp-p
200mV /div
e 20psec/div
Figure 2-12.
Ajustment of FM 3.8 MHz and 4.8 MHz
Measuring
instrument
Test point TP203 ,
ee ie 1¢201) |Video Signal
R222 (FM R220 (deviation
carrier control) | control)
3.8 MHz 1.0 + 0.05 Vp-p
Specification
Note. 1:
Carry out this adjustment only when 1C201 has —
31
Vs O R £-18
VC-730ET
completely adjusted.
Note. 2:
The video output terminal should be terminated
with a 75-ohm impedance.
1. First make sure that the EE level playback video
signal is at the speciffied level.
2. Place the unit in the record mode and get it
ready for external input.
Note:
Do not connect anything to the external input
terminal.
3. Hook up the frequency counter to TP203.
Adjust R222 (FM carrier control) so that the
counter reading be 3.8 MHz.
Note:
Make sure the white and dark clip controls are
not now applied to the waveform.
4. Feed the colour bar signal (stair-case waveform)
and make self-recording and playback.
5. Observe the video output terminal voltage
(across the terminal resistor) on the oscilloscope
screen. If the playback video signal level is below
1.0 Vp-p, turn R220 (deviation control) clockwise.
If above 1.0 Vp-p, turn the control counter-
clockwise. Now make self-recording and playback
again.
6. Repeat the above step 5 to finally get the
playback video signal level at 1.0+0.05 Vp-p, as
shown in Fig. 2-12.
Adjustment of white clip
Oscilloscope
Standard colour bar
(stair-case waveform)
TP201
R225 (white clip control)
+ 0
. Place the unit to the record mode.
. Feed the colour bar (stair-case waveform) signal.
3. Observing the output at TP201, adjust R225
(white clip control) so that the white peak
overshoot be 80 (tolerance +0-10)%.
Measuring
instrument
Input signal
Test point
Adjusting point
Specification
NM —
WHITE
CLIP
80%
100%
DARK ~-
CLIP
50%
200mvV /div
20pusec/div
Figure 2-13.