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Adiustment of FM 3.8 MHz and 4.8
Frequency
Measuring
counter
instrument
Mode
Recording
Adjusting
carrier control) control)
point
Specification 3.8
M H z + 50kHz
Note :
Carry out this adjustment only when IC201 has
or the deviation (4.8 MHz) is found apparently out
of specification.
Make this adjustment after the EE level has been
completely adjusted.
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 TP205 and
TP202. Adjust R227 (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 and make self-
recording and playback.
5. Observe the voltage of pin @ of IC201 (video
output) on the oscilloscope screen.
playback video signal level is above 2.0 Vp-p,
turn R228 (deviation control) clockwise.
If below 2.0 Vp-p, turn the control counter-
clockwise.
N o w m a k e s e l f - r e c o r d i n g a n d
playback again.
6. Repeat the above step 5 to finally get the
playback video signal level at 2.0 2 0.08 Vp-p, as
shown in Figure 2-7.
M
HZ
Osci I loscope
Self-recording/
R228 (Deviation
2.0 + O.O8Vp-p
If the
38
Figure 2-7.
Adjustment of recording current
Measuring
I Osci I loscope
instrument
Recording
Mode
Input signal
Standard colour bar
(stair-case waveform)
Test point
External trigger
(video output terminal)
Adjusting
R255
point
(recording FM
control)
Sync tip level:
tion
1 4 0 + IOmVp-p 2 4 + ZmVp-p
Note:
2. Feed the colour bar signal to the video input
terminal.
3. Observing the waveform on the oscilloscope
screen (external trigger at pin 8 of IC201 (video-
output)), take the following steps.
a) Connect the oscilloscope' s ground and signal
leads to TP302 and TP301, respectively.
imum.
c) Adjust R518 (recording chroma control) so
that the red level be 24 + ZmVp-p as shown in
Figure 2-9.
4. Adjust R255 (recording FM control) so that the
sync tip be 140 t IOmVp-p as shown in Figure
- - 1
(recording
Red level:
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