Panasonic JU-475-4, Service Manual

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4. OUTLINE OF MAINTENANCE
• The fo llo w in g tools are required fo r maintenance o f an FDD.
4.1 Alignm ent Diskette
A lig n m e n t diskette is used fo r head actuator alignm ent and index sensor adjustment.
Use the rig h t diskette as shown in Table 8.1.
4.2 Exerciser
The exerciser enables you to make all adjustments and inspections necessary fo r an FDD. Its
functions include the follo w in g.
(1)
Seek increm ent or alternate tracks
(2) Read (but no data compare)
(3) W rite 1F or 2F (All "0"s or " 1 "s)
(4) Head load (5.25inch FDD w ith 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 th a t occur because o f the w rong operating procedure, w rong programm ing, the use o f a
defective diskette, or soft errors due to external causes, such as contaminated air and random
electrical noise, are often attribu te d to an FDD failure.
Unless a visual inspection o f the FDD reveals an evident assembly fa u lt or a defect, always confirm
errors w ith another good diskette, and another know n good FDD.
5.2 Soft Error Detection and Correction
Soft errors are norm ally caused by the fo llo w in g .
(1) Contam ination between read/w rite heads and diskette. This kind o f contam ination can be
easily elim inated by the liner in the diskette. Please fo llo w the appropriate procedures
provided w ith the cleaning diskette.
(2) Random electrical noise, norm ally a fe w microseconds or less.
(3) Small defects in w ritte n data and/or track not detected during w rite operation may cause
soft errors during read.
(4) Faulty grounding o f the FDD or host system can also cause soft errors.
(5) W rong m otor speed is another cause o f soft errors.
Take the fo llo w in g steps on the controller side to recover from the soft errors mentioned
above.
(1) Read the track again ten times or u ntil 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 th a t cannot be corrected by the above procedure is irrecoverable.
5.3 W rite Error
If an error occurs during w rite operation, it is usually detected during the next revolution by
perform ing a read operation called w rite check. To correct an error, w rite again and repeat a
w rite check operation. If the result is unsatisfactory afte r ten or more w rite operations, perform a
read operation on another track to determ ine w hether it is the diskette or the drive th a t is w rong.
If an error persists, replace the diskette and repeat the above procedure.
If the error still persists, assume the FDD defective. If the e rro r is corrected, the diskette is
defective. It can be throw n away.