IBM System/34 Maintenance Manual page 403

27-900
CAUTION
DISKETrE 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.
27-910 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 OE 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 72MD.
• A worn 53FD or 72MD 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.
27-920 Diskette 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
(physical cylinder, 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 did not
compares 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.
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