Coarse Adjustment Of Phase; Flatness Check Of Fm Waveform - Mitsubishi HS-U748 Service Manual

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3-2-4. Coarse Adjustment of Phase

1. Play back an alignment tape (NM6KE2 : 859C339O90).
2. Preset the tracking.
3. Observe the FM Waveform after performing Item 3-2-
1. "GUIDE ROLLER Check".
4. If the amplitude level of the FM Waveform is low as in
(F) in Fig. 3-2-4, set it at the maximum level as in (G),
according to the following procedure. Loosen the
Screws D and E and insert a screw driver (+) into the
Hole in the MAIN PLATE ASSY (Part A). Then, move
the A/C PLATE to the right and left to set the
amplitude level to maximum.
5. Tighten the Screws D and E.

3-2-5. Flatness Check of FM Waveform

1. Play back an alignment tape (NM6KE2 : 859C339O90).
2. Adjust the tracking and confirm that the amplitude of
the FM signal remains flat.
Note : Adjust the tracking manually, according to the
following procedure.
• Turn the Shuttle Ring of the product during
PLAYBACK for manual tracking adjustment.
• Press the 3DSP button to switch the tracking
adjustment from "Manual" to "Auto".
3. Adjust the tracking so that the amplitude level of the
FM Waveform will be at the maximum. Set the
oscilloscope so that the amplitude level of the FM
Waveform is 5 divisions on the oscilloscope.
4. Adjust the tracking so that the peak of the FM Output
Waveform is 4 divisions. Confirm that the FM
Waveforms (B), (C), (D) and (E) are within the range
of the specified values in the Fig. 3-2-5.
5. If the Waveforms are out of the specified values in
step 4, repeat the Item 3-2. "Check and Adjustment of
FM Envelope" from the beginning.
Screw D
Tape
Screw E
Part A
(F)
(G)
B
D
0.2 division
B, C
D, E
- 32 -
Fig. 3-2-3
Fig. 3-2-4
E
4 divisions
0.2 division
In VHS mode
3.0 divisions or more
1.0 division or more
Fig. 3-2-5
C

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