Sharp DV-NC70U Service Manual - Page 30

Head switching pulse, Notes, ure 8-34

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DV-NC70U/C DV-NC72U Notes: 1. Previously set the tracking control in the center position, and adjust the ATR signal waveform to maximum with X value adjustment nut. Thereby the tape run rough adjustment is facilitated. 2. Especially the outlet side ATR signal waveform must have higher flatness. Figure 8-28. 2. Adjustment of A/C head height and azimuth 1 Perform the initial setting of A/C head position by the method stated in "8-17 Replacement 3". 2 Connect the oscilloscope to the audio output terminal. 3 Using the alignment tape in which 1 kHz linear audio signal has been recorded, adjust the height screw so as to get max audio output. 4 Using the alignment tape in which 7 kHz linear audio signal has been recorded, adjust the azimuth screw so as to get max audio output. 5 The adjustment of 3 and 4 twice or three times repeat, and finally adjust 4. 3 Next, press the tracking button (+), (-) and change the ATR signal waveform from max to min and from min to max. At this time adjust the height of supply and take-up side guide roller with the adjustment driver (JiGDRiVERH-4) so that the ATR signal waveform changes nearly parallel. 4 If the tape is lifted or sunk from the helical lead surface, the PB ATR signal waveform appears as shown in Figure 8-31. 5 Press the tracking button (+), (-) and make sure that the ATR signal waveform changes nearly parallel. 6 Finally, check tape crease near the reverse guide. If tape crease is found, adjust tilt screw 45˚ counter clockwise. Small tape crcase will appear at retain guide after this adjustment finished. PB ATR Signal Head switching pulse Figure 8-30. For X value adjustment Adjust the X value, turning the geartype screwdriver. Figure 8-29. 3. Tape run adjustment 1 Connect the oscilloscope to PB ATR signal output test point, set oscilloscope sync to EXT, trigger-input the PB CHROMA signal (head switching pulse). 2 Rough adjustment of X value Tentatively fix A/C head arm screws 1 by the method described in "8-17 Replacement 3". Playback the alignment tape (VROATSV) and shortcircuit between TP801 and TP802. As a result the auto-tracking is automatically cancelled, so that the X value adjustment mode is set. Move the A/C head with the X value adjustment gear driver (JiGDRiVER-6) by the method shown in Figure 8-34, and adjust the A/C head so as to get the maximum ATR signal waveform. (Note: When the A/ C head is adjusted, adjust so that the maximum ATR signal waveform is obtained nearest the position of initial setting made in 8-17.) 30

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30
DV-NC70U/C
DV-NC72U
3
Next, press the tracking button (+), (–) and change
the ATR signal waveform from max to min and from
min to max. At this time adjust the height of supply
and take-up side guide roller with the adjustment
driver (JiGDRiVERH-4) so that the ATR signal wave-
form changes nearly parallel.
4
If the tape is lifted or sunk from the helical lead
surface, the PB ATR signal waveform appears as
shown in
Figure 8-31
.
5
Press the tracking button (+), (–) and make sure that
the ATR signal waveform changes nearly parallel.
6
Finally, check tape crease near the reverse guide. If
tape crease is found, adjust tilt screw 45˚ counter
clockwise. Small tape crcase will appear at retain
guide after this adjustment finished.
PB ATR
Signal
Head switching pulse
Figure 8-30.
Notes:
1.
Previously set the tracking control in the center position,
and adjust the ATR signal waveform to maximum with X
value adjustment nut. Thereby the tape run rough ad-
justment is facilitated.
2. Especially the outlet side ATR signal waveform must
have higher flatness.
2.
Adjustment of A/C head height and azimuth
1
Perform the initial setting of A/C head position by the
method stated in "
8-17
Replacement 3".
2
Connect the oscilloscope to the audio output termi-
nal.
3
Using the alignment tape in which 1 kHz linear audio
signal has been recorded, adjust the height screw so
as to get max audio output.
4
Using the alignment tape in which 7 kHz linear audio
signal has been recorded, adjust the azimuth screw
so as to get max audio output.
5
The adjustment of
3
and
4
twice or three times
repeat, and finally adjust
4
.
Figure 8-28.
For X value adjustment
Adjust the X value, turning the gear-
type screwdriver.
Figure 8-29.
3.
Tape run adjustment
1
Connect the oscilloscope to PB ATR signal output
test point, set oscilloscope sync to EXT, trigger-input
the PB CHROMA signal (head switching pulse).
2
Rough adjustment of X value
Tentatively fix A/C head arm screws
1
by the method
described in "
8-17
Replacement 3".
Playback the alignment tape (VROATSV) and
shortcircuit between TP801 and TP802. As a result
the auto-tracking is automatically cancelled, so that
the X value adjustment mode is set.
Move the A/C head with the X value adjustment gear
driver (JiGDRiVER-6) by the method shown in
Fig-
ure 8-34
, and adjust the A/C head so as to get the
maximum ATR signal waveform. (Note: When the A/
C head is adjusted, adjust so that the maximum ATR
signal waveform is obtained nearest the position of
initial setting made in
8-17
.)