Fujitsu M255XK Customer Engineering Manual page 49

4.4.9 Resolution
Tools Required: Work Disk
Exerciser (AVA 409 or equivalent)
Oscilloscope
1. Connect the oscilloscope channels to TP1 and TP2. Set the oscilloscope to
AC mode, both channels to 50 millivolts per division, and 1 microsecond per
division time base.
Put one of the channels in invert mode, and put both channels to ADD.
2. Start the Spindle Motor and load the level disk.
3. Seek the Read/Write heads to the innermost track.
4. Record and then read the innermost track with a constant "IF" (WRITE DATA
frequency with only O's recorded of 125kHz for the M2552K and 250kHz for
the M2553/54K).
5. Measure the average read level (shown as V1F in Figure 4-10).
6. Record and then read the innermost track with a constant "2F" (WRITE OAT A
frequency with only l's recorded is 250kHZ for the M2552K and 500kHZ for
the M2553/54K - double the IF of step 4).
7. Measure the average read level (shown as V2F in Figure 4-10).
ADD
Figure 4-10 Resolution Measurement
8. Use the measured values of V1F and V2F in the following formula:
Resolution (true value)
=
V2F X 100
V1F
9. Ensure the innermost track Resolution (true value) is 60% or more.
10. Repeat steps 4 through 9 for side 0 and side
1.
11. If the results are not within the indicated range, the following items are
probable causes:
(a) Faulty Diskette. Replace the diskette if it is bent or damaged.
(b) Abnormal disk speed. Refer to paragraph 4.4.5.
(c) Faulty head contact. Refer to paragraph 4.4.6.
(d) Faulty head. Refer to paragraph 4.5.1.
(e) Faulty circuit card. Refer to paragraph 4.5.6.
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