Panasonic JU-363 Service Manual page 8

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Fig. 4.1 Modulation
4.5 Radial Alignment
Normally, this adjustment is not necessary.
If the stepping motor mounting screws have loosened, or if parts have been damaged, or if a compatibility error has
occurred, check and re-adjust as follows:
Steps 1 through 4 apply to both the CE and DAD types, except that alignment diskettes are different between them.
1. Insert an alignment diskette.
Caution: Be sure to leave the alignment diskette indoors for 20 minutes before starting radial alignment.
2. Step to tra.ck 40.
3. Synchronize oscilloscope on IX (- INDEX), and set time base to 20 ms/division. One revolution will be displayed.
4. Connect one probe to T1 and the other to T2. Ground the probes to GND and AG. Set inputs to AC, Add, and
invert one channel. Set vertical deflection to 0.1 V/division (VARIABLE PULL) for the CE type, or to 2 mV/
division for the DAD type.
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Cat's Eye Type
5. Check amplitude waveforms for Side 0 and Side 1. Waveforms such as shown .in Fig. 4.2 can be seen.
6. The amplitude ratio of the two waveforms should be 65% or more. If it is not, adjust as follows:
7. Loosen the two stepping motor mounting screws.
8. Turn the stepping motor along the base by hand until the lobes of the two waveforms have approximately the same
amplitude, and retighten the mounting screws. (See Fig. 4.2.)
9. Seek from track 0 to 40 and from track 79 to 40, and check that radial alignment is correct.
10. After radial adjustment, be sure to make track 00 sensor adjustment (4.8) and check carriage limiter (4.9).
Fig. 4.2
Radial Alignment Waveforms (Cat's Eye)
Caution: Sides O and 1 are adjusted to agree at the factory, but if they differ from each other, readjust them to be
65% or more.
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