Outline Of Maintenance; Alignment Diskette; Exerciser; Diagnostic Procedures - Panasonic JU-475-4 Service Manual

4. OUTLINE OF MAINTENANCE
• The following tools are required for maintenance of an FDD.
4.1 Alignment Diskette
Alignment diskette is used for head actuator alignment and index sensor adjustment.
Use the right diskette as shown in Table 8.1.
4.2 Exerciser
The exerciser enables you to make all adjustments and inspections necessary for an FDD. Its
functions include the following.
(1) Seek increment or alternate tracks
(2) Read (but no data compare)
(3) Write 1For2F(AII "O"sor"1"s)
(4) Head load (5.25inch FDD with optional head loader)
(5) Recalibration to track 0
The exerciser has switches and indicators to execute a specified function.
5. DIAGNOSTIC PROCEDURES
5.1 Error Symptom Recognition
Errors that occur because of the wrong operating procedure, wrong programming, the use of a
defective diskette, or soft errors due to external causes, such as contaminated air and random
electrical noise, are often attributed to an FDD failure.
Unless a visual inspection of the FDD reveals an evident assembly fault or a defect, always confirm
errors with another good diskette, and another known good FDD.
5.2 Soft Error Detection and Correction
Soft errors are normally caused by the following.
(1) Contamination between read/write heads and diskette. This kind of contamination can be
easily eliminated by the liner in the diskette. Please follow the appropriate procedures
provided with the cleaning diskette.
(2) Random electrical noise, normally a few microseconds or less.
(3) Small defects in written data and/or track not detected during write operation may cause
soft errors during read.
(4) Faulty grounding of the FDD or host system can also cause soft errors.
(5) Wrong motor speed is another cause of soft errors.
Take the following steps on the controller side to recover from the soft errors mentioned
above.
(1) Read the track again ten times or until the data is recovered.
(2) If step (1) above fails to recover the data, access the adjacent track. Then return the head to
the original track.
(3) Repeat step (1).
(4) Any error that cannot be corrected by the above procedure is irrecoverable.
5.3 Write Error
If an error occurs during write operation, it is usually detected during the next revolution by
performing a read operation called write check. To correct an error, write again and repeat a
write check operation. If the result is unsatisfactory after ten or more write operations, perform a
read operation on another track to determine whether it is the diskette or the drive that is wrong.
If an error persists, replace the diskette and repeat the above procedure.
If the error still persists, assume the FDD defective. If the error is corrected, the diskette is
defective. It can be thrown away.
- 2-