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Adjustment of FM 3.8 MHz and 4.8 MHz )
Measuring
| Frequency
.
Recording
Self-recording /
playback
Inputsignal
|Externalinput
|Standard colour
(no signal)
bar (stair-case
waveform)
Test point
TP301 (Sig)
Video Output
TP302 (GND)
terminal
Adjusting
R205 (FM carrier | R204 (deviation
point
control)
control)
3.8MHz + 50kHz |1.0 + 0.04 Vp-p
Note. 1:
Carry out this adjustment only when
IC201 has
been replaced or when the carrier setting (3.8 MHz)
or the deviation (4.8 MHz) is found apparently out
of specification.
Make this adjustment after the EE level has been
completely adjusted.
Note. 2:
The video output terminal should be terminated
with a 75-ohm impedance.
1. First make sure that the EE video signal level is at
the specified 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 TP301
and
TP302. Adjust R205 (FM carrier control) so that
the counter reading be 3.8 MHz.
Note:
Make sure the white clip control is 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 above
1.0 Vp-p, turn R204 (deviation control) clockwise.
If below
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
+0.04 Vp-p, as
shown in Figure 2-5.
Figure 2-5.
35
VC-A30G(BR) VC-A30S(BR)
VC-A30GM(BR) VC-A30SM(BR)
VC-A30Q0MI(BR) VC-A30SV(BR)
Adjustment of white clip
Measuring
.
Mode
| Recording
Input signal
Standard colour bar
(stair-case waveform)
Test point
TP201
Adjusting point
R206 (white clip control)
Specification
80+4%
1. Place the unit to the record mode.
2. Feed the colour bar signal to the video input
terminal.
3. Turn R205 clockwise to maximum position.
4. Observing the output at TP201, adjust R206
(white clip control) so that the white peak
overshoot be 80 + 4%.
5. Make sure that the dark peak overshoot is 50 +
10%.
WHITE
CLIP
80%
100%
Jy
DARK
a
200mVidiv
Figure 2-6.
Adjustment of recording current
Measurin
E
instru ment
Oscilloscope
Input signal
Standard colour bar
(stair-case waveform)
Test point
TP301 (GND at TP302)
External trigger
(video output terminal)
R208
R504
(recording Y
(recording
control)
chroma control)
Specifica-
| Sync tip level
Red level
tion
140 + 10mVp-p | 24 + 2mVp-p
Note:
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