Table of Contents
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General Information
1-1.
INTRODUCTION
The Hewlett-Packard 7957A and HP 7958A Disc
Drives are random access, data storase devices
designed for use with small and medium sized
computer
systems.
The
formatted
storage
capacities of the HP 7957 A and HP 7958A are 81
megabytes and 130 megabytes, respectively. In this
manual, unless otherwise specified, "disc drive"
refers to the HP 7957A and HP 7958A.
The disc drive employs three (HP 7957 A) or five
(HP
7958A)
nonremovable
130-millimetre
(5.12-inch) discs for storage media. Each disc sur-
face employs one movable head to service its data
tracks. The bottom surface of the lowest disc in
the stack contains continuous prerecorded servo
data which is used to ensure the precise positioning
of the read/write heads.
Head positioning is performed by a rotary actuator
and
a
closed-loop
servo
positioning
system.
Mechanical and contamination protection for the
discs, heads, and the rotary actuator is provided by
a sealed head-disc module. The head-disc module
includes a self-contained air filtration system
which supplies clean air and temperature equaliza-
tion throughout the module.
Also
included
in
the
disc
drive
are
a
Hewlett-Packard Interface Bus (HP-IB) controller
and a power supply.
The disc drive contains internal self-test diagnostics
and a fault-finding system which exercise key
functions of the disc drive. Self test is performed
automatically at power on and can also be in-
itiated by the host. Go/no-go test results are indi-
cated by a green/red indicator on the front panel.
If a failure occurs, information on the cause of the
failure can be determined by viewing the status of
the green/red indicators.
The disc drive is packaged in a stand-alone desktop
cabinet. AClcessories available include a desk-height
stand-alone cabinet designed to hold the disc drive
and other desktop stack modules. A kit for rack
1
mounting the disc drive in a standard EIA
equipment rack is also available.
This manual provides all the service information
needed to maintain the disc drive. Details of the
control functions provided by the host computer
are described in the installation documentation
provided with the computer.
1-2.
SCOPE OF MANUAL
The manual is divided into six chapters as follows:
a. Chapter 1 contains a general description of the
disc drive.
b. Chapter 2 provides information about the ESDI
Interface between the controller PCA and the
head disc assembly (HDA).
It
also contains in-
formation on CS/80 Command Set implementa-
tion, Request Status Summary and Utility
Command summary.
c. Chapter 3 describes the operating principles of
the disc drive.
d. Chapter 4 contains servicing information for the
disc drive, including instructions on how to use
the diagnostics tools.
e. Chapter 5 supplies step-by-step removal and
replacement procedures for all field-replaceable
assemblies and parts in the disc drive.
f. Chapter 6 lists and illustrates all of the field-
replaceable assemblies and parts in the disc
drive.
Appendix A provides a listing and copy of all the
service notes applicable to the HP 7957 A and HP
7958A Disc Drives.
1-1
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