Diskette Quality And Head Wear Service Check - IBM System/34 Maintenance Manual

25-991
CAUTION
DISKETTE QUALITY AND HEAD WEAR
SERVICE CHECK
The diskette quality and head wear service check must
be performed with the diskette drive in the same
position as when installed or the results might not be
accurate.
A new head will write and read correctly on most
diskettes. As the head wears, the quality of the diskette
becomes more important. The tests described in this
paragraph will aid in determining the quality of the
diskette and the condition of the head.
Note: Some of the failures indicated by these tests
cannot always be repeated.
Inspect the diskette failure descriptions, print the ERAP
error history table, and run the following tests as
necessary to verify the errors indicated by the ERAP.
25-992 Diskette Failure Descriptions
• A bump, scratch, crease, or fingerprint causes errors
on the same sectors, usually across tracks that are
next to each other.
• Too large of a center hole causes errors on sectors
that are on opposite sides of the center hole.
(Example: sectors hexadecimal 01 and DE or sectors
hexadecimal 06 and 13.)
• Material from the diskette jacket cause random
errors.
• A diskette written by a worn 33FD head causes
random read errors on cylinders hexadecimal 2B
through 4C when read by a 53FD.
• A worn 53FD head causes read errors on the inner
tracks area of the diskette (cylinders hexadecimal 40
through 4C) when using MFM mode. If there are
failures in this area, suspect a worn head. TUs E1,
9A, and 9B may be run to indicate the quality of the
head in your system.
25-993 Test Descriptions
Diskette analysis-This routine reads the complete
diskette (written in any IBM format) and causes a
printout, which identifies the locations (logical cylinder,
head, and sector) of any failures. Each sector is read
only once (without trying again). To run this routine:
1. Perform a CSIPL from the DIAGB1 diskette.
2. Select the UTILITIES option on the main menu.
3. Select the EC UPDATE COpy option.
The following three tests are diskette TUs and are
selected after taking the TU SELECT option on the main
menu. (For easier use, set the Address/Data switches
to F800 (CE panel) and perform an IPL before running
the TUs.)
CAUTION
The following three TUs write on the diskette.
TU E1-This TU runs only on a diskette 20. This
TU writes on each sector of the diskette and then
reads each sector of the diskette. The' switch filter' line
is off (not normal) when cylinders hexadecimal 3D
through 4C are read. A printout identifies the location
(cylinder1, head, sector, byte, and bit) of any failures.
Because of the pattern written by this TU and because
the' switch filter' line is off while reading the inner
cylinders, the printout may indicate failures not found by
the diskette analysis routine or failures not indicated by
ERAP. Four or more data bytes that do not compare per
track on cylinders hexadecimal 48 through 4C indicates
that TU 9A should be run.
Note: The location of a failure indicated by this TU may
be used when scoping diskette damage using the read
loop exerciser.
1The cylinder number is the number of the logical cylinder if
a level 1 attachment is installed. If a level 2 attachment
is installed, the identified cylinder is the physical cylinder.
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25-991
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