Seagate ST43401N-ND, ST43402ND User Manual

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Elite Disc Drive

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST43401N/ND

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

ST43402ND

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

User ’s Manual

○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○○

Contents

Preface ................................................................................................... iii

Electrostatic discharge protection....................................................... iii

Important safety information and precautions..................................... iv

Wichtige Sicherheitshinweise ......................................................... vi

Technical support services ............................................................. ix

Section 1. General description............................................................... 1

Section 2. Installation............................................................................. 7

Abschnitt 2. Installation................................................................... 7

Section 3. Operation.............................................................................. 43

Section 4. Parts data ............................................................................. 49

Section 5. Maintenance ......................................................................... 51

© 1994 Seagate Technology, Inc. All rights reserved
Publication number: 83327720, Rev. B
December 1994

Seagate®, Seagate Technology®, and the Seagate logo are registered
trademarks of Seagate Technology, Inc. Elite™, SeaFAX™, SeaFONE™,
SeaTDD™, and SeaBOARD™ are trademarks of Seagate Technology, Inc.
Other product names are registered trademarks or trademarks of their
owners.

Seagate reserves the right to change, without notice, product offerings or
specifications. No part of this publication may be reproduced in any form
without written permission from Seagate Technology, Inc.

ST43401N/ND, ST43402ND User’s Manual, Rev. B iii

Preface

This manual contains information for users of Seagate® ST43401N/ND and
ST43402ND Elite™ disc drives. It provides instructions to all personnel who
operate the drive and to customer engineers who install and check out the
drive. Additional information is available in the reference manual (publication

83327730).

Electrostatic discharge protection

Caution. Removal of circuit boards by personnel not performing depot repair

will damage components and may void the warranty.

All drive electronic assemblies are sensitive to static electricity due to the
electrostatically sensitive devices used within the drive circuitry. Although
some devices such as metal-oxide semiconductors are extremely sensitive,
all semiconductors, as well as some resistors and capacitors, may be
damaged or degraded by exposure to static electricity.

Electrostatic damage to electronic devices may be caused by the direct
discharge of a charged conductor, or by exposure to the static fields surround­ing charged objects. To avoid damaging drive electronic assemblies, service
personnel must observe the following precautions when servicing the drive:

• Ground yourself to the drive whenever the drive electronics are or will be
exposed. Connect yourself to ground with a wrist strap (Seagate part
number 12263496). Connection may be made to any grounded metal
assembly. As a general rule, remember that you and the drive electronics
must all be grounded to avoid potentially damaging static discharges.

• Turn off power before removing or installing the DC power cable.

• Do not remove any circuit boards from the drive.

• Never use an ohmmeter on any circuit boards.

iv ST43401N/ND, ST43402ND User’s Manual, Rev. B

Important safety information and precautions

Caution. Use forced-air ventilation when bench-testing the drive to ensure

proper cooling of drive components.

Use proper safety and repair techniques for safe, reliable operation of this unit.
Service should be done only by qualified persons. We recommend the
procedures in this manual as effective ways of servicing the unit. Some
procedures require the use of special tools. For proper maintenance and
safety, you must use these tools as recommended.

The procedures in this manual and labels on the unit contain warnings and
cautions that must be carefully read and followed to minimize or eliminate the
risk of personal injury. The warnings point out conditions or practices that may
endanger you or others. The cautions point out conditions or practices that
may damage the unit, possibly making it unsafe for use.

You must also understand that these warnings and cautions are not exhaus­tive. We cannot possibly know, evaluate, and advise you of all the ways in
which maintenance might be performed or the possible risk of each technique.
Consequently, we have not completed any such broad evaluation. If you use
a non-approved procedure or tool, first ensure that the method you choose will
not risk either your safety or unit performance.

Always observe the following warnings and precautions:

• Perform all maintenance by following the procedures in this manual.

• Follow all cautions and warnings in the procedures.

• Use sound safety practices when operating or repairing the unit.

• Use caution when troubleshooting a unit that has voltages present. Remove
power from the unit before servicing it.

• Wear safety shoes when removing or replacing heavy parts.

• Ensure that the internal temperature of the rack or cabinet will not exceed
the limits defined for the drive when the drive is mounted in an equipment
rack or cabinet. When units are stacked vertically, pay special attention to
the top where temperatures are usually highest.

• Follow the precautions listed under “Electrostatic discharge protection.”

ST43401N/ND and ST43402ND User’s Manual, Rev. B v

• Do not remove any circuit boards from the drive chassis. Return the entire
drive for depot repair if any circuit board is defective. Removal of circuit
boards by personnel not performing depot repair will damage components
and may void the warranty.

• Do not remove the head and disc assembly (HDA) from the drive chassis.
Return the entire drive for depot repair if the HDA is defective.

• Do not attempt to disassemble the HDA. It is not field repairable. If the sealed
HDA is opened by personnel not performing depot repair, this will damage
components and void the warranty.

• As a component, this drive is designed to be installed and operated in
accordance with UL1950, IEC950, EN60950, CSA C22.2 950, and VDE0805.

• Ensure that the power supply meets the specifications in this manual and
is designed to be used in accordance with UL1950, IEC950, EN60950, CSA
C22.2 950, and VDE0805.

Seagate takes all reasonable steps to ensure that its products are certifiable
to currently accepted standards. Typical applications of these disc drives
include customer packaging and subsystem design. Safety agencies condi­tionally certify component assemblies, such as the Elite disc drive, based on
their final acceptability in the end-use product. The subsystem designers are
responsible for meeting these conditions of acceptability in obtaining safety/
regulatory agency compliance in their end-use products and in certifying
where required by law. A necessary part of meeting safety requirements is the
provision for overcurrent protection on drive SELV supply voltages.

This unit is a component part and as such is not meant to comply with FCC
or similar national requirements as a stand-alone unit. Engineering radiated
and conducted emissions test results are available through the Seagate
Safety Department to assist the subsystem designer.

vi ST43401N/ND, ST43402ND User’s Manual, Rev. B

Wichtige Sicherheitshinweise

Vorsicht. Beim Testen des Laufwerks auf dem Prüftisch ist Fremdbelüftung

vorzusehen, um eine ausreichende Kühlung der Laufwerkkomponenten
sicherzustellen.

Verwenden Sie geeignete Sicherheits- und Reparaturverfahren, um den
sicheren, zuverlässigen Betrieb dieser Einheit zu gewährleisten. Reparaturen
dürfen nur von qualifiziertem Fachpersonal vorgenommen werden. Wir
empfehlen die Verfahren in diesem Handbuch als effektive Methoden zur
Wartung und Reparatur der Einheit. Einige Verfahren erfordern
Spezialwerkzeuge; diese müssen zur sachgemäßen Ausführung der
Wartungsarbeiten und aus Sicherheitsgründen den Empfehlungen
entsprechend verwendet werden.

Die Verfahren in diesem Handbuch und die Aufkleber auf dem Gerät enthalten
Warn- und Vorsichtshinweise. Diese Hinweise sind sorgfältig durchzulesen
und zu beachten, um das Risiko von Verletzungen auf ein Mindestmaß zu
beschränken oder ganz zu vermeiden. Die Warnhinweise machen auf
Situationen oder Praktiken aufmerksam, die Sie oder andere gefährden
könnten. Die Vorsichtshinweise machen auf Situationen oder Praktiken
aufmerksam, die die Einheit beschädigen können, so daß deren Gebrauch mit
Risiko behaftet ist.

Die Warn- und Vorsichtshinweise sind nicht allumfassend! Es ist uns einfach
nicht möglich, alle Wartungsmethoden oder die eventuellen Risiken jeder
Methode zu kennen, zu beurteilen und Sie entsprechend zu beraten. Aus
diesem Grund haben wir auf eine derartige umfassende Beurteilung verzichtet.
Falls Sie ein hier nicht beschriebenes Verfahren oder Werkzeug verwenden,
stellen Sie zuerst sicher, daß das gewählte Verfahren weder Ihre persönliche
Sicherheit noch die Leistung der Einheit gefährdet.

Beachten Sie in jedem Fall die folgenden Warn- und Vorsichtshinweise:

• Führen Sie alle Wartungsarbeiten entsprechend den Anweisungen in
diesem Handbuch aus.

• Beachten Sie alle Warn- und Vorsichtshinweise in diesem Handbuch.

• Treffen Sie beim Betrieb oder bei der Reparatur der Einheit angemessene
Sicherheitsvorkehrungen.

• Wenn eine Einheit unter Spannung steht, gehen Sie bei der Fehlerdiagnose
besonders vorsichtig vor. Schalten Sie die Einheit aus, bevor Sie mit den
Reparaturarbeiten beginnen.

ST43401N/ND, ST43402ND User’s Manual, Rev. B vii

• Tragen Sie Sicherheitsschuhe, wenn Sie schwere Teile aus- bzw. einbauen.

• Wenn das Laufwerk in einem Einbaugestell oder Gehäuse montiert ist,
sorgen Sie dafür, daß die Temperatur im Inneren des Gestells oder
Gehäuses die für das Laufwerk vorgegebenen Grenzwerte nicht übersteigt.
Wenn Einheiten vertikal gestapelt werden, achten Sie besonders auf den
oberen Stapelbereich, da dort die Temperatur gewöhnlich am höchsten ist.

• Befolgen Sie die oben unter “Electrostatic Discharge Protection”
angegebenen Sicherheitsmaßnahmen.

• Nehmen Sie keine Platinen aus dem Laufwerkgehäuse. Wenn eine Platine
defekt ist, muß das gesamte Laufwerk zur Reparatur eingeschickt werden.
Die Herausnahme von Platinen durch andere Personen als die für die
werkseitige Reparatur zuständigen kann zu einer Beschädigung der
Komponenten und Erlöschen des Garantieanspruchs führen.

• Die vormontierte Kopf- und Festplatteneinheit (HDA) nicht aus dem
Laufwerkgehäuse nehmen! Falls die HDA beschädigt ist, schicken Sie das
gesamte Laufwerk zur Reparatur ein.

• Die HDA ist nicht vor Ort reparierbar und darf nicht auseinandergenommen
werden! Öffnen der versiegelten HDA durch andere Personen als die für die
werkseitige Reparatur zuständigen hat eine Beschädigung der Komponenten
und Erlöschen des Garantieanspruchs zur Folge.

• Als Teilkomponente ist dieses Laufwerk für die Installation und den Betrieb
in Übereinstimmung mit UL 1950, IEC950, EN60950, CSA C22.2 950 und
VDE0805 vorgesehen.

• Achten Sie darauf, daß Ihr Netzteil den technischen Daten in diesem
Handbuch entspricht und für den Betrieb in Übereinstimmung mit UL 1950,
IEC950, EN 60950, CSA C22.2 950 und VD0805 vorgesehen ist.

Seagate ist ständig bemüht, die Zulassungsfähigkeit von Seagate-Produkten
im Rahmen der gegenwärtig geltenden Standards zu gewährleisten. Zu den
typischen Anwendungen dieser Festplattenwerke zählen Systemeinbau durch
den Kunden und die Konstruktion von Untersystemen. Sicherheitsbehörden
gewähren eine bedingte Zulassung für Komponenten wie das Elite­Festplattenlaufwerk vorbehaltlich der endgültigen Zulasssung im Endprodukt.
Designer von Untersystemen sind dafür verantwortlich, die Voraussetzungen
für die Einhaltung sicherheits- oder aufsichtsbehördlicher Vorschriften in
ihren Endprodukten und - falls gesetzlich vorgeschrieben - für die Zulassung
zu schaffen. Eine Grundvoraussetzung zur Einhaltung der
Sicherheitsanforderungen ist die Bereitstellung eines Überlastschutzes auf
den SELV-Versorgungsspannungen des Laufwerks.

viii ST43401N/ND, ST43402ND User’s Manual, Rev. B

Dieses Gerät ist eine Baugruppe und unterliegt als solche nicht den
Anforderungen der FCC oder ähnlicher nationaler Behörden für eigenständige.
Technische Testergebnisse zu Frequenz- und Elektrizitätsemissionen sind
für Designer von Untersystemen auf Anfrage von der Seagate­Sicherheitsabteilung erhältlich.

ST43401N/ND, ST43402ND User’s Manual, Rev. B ix

Technical support services

Seagate Technology provides technical support literature and diagnostic
utilities to authorized distributors. Please contact your dealer for technical
support and installation troubleshooting. Product technical support is avail­able for all Seagate products by calling the SeaFAX™, SeaFONE™,
SeaTDD™, or SeaBOARD™ services. These are toll calls if you dial from
outside of the number’s local dialing area.

SeaFAX:
USA [phone]; England 44-62-847-7080

Use a touch-tone telephone to access Seagate’s automated FAX system and
select technical support information by return FAX. This service is available
24 hours a day, 7 days a week.

SeaFONE: [phone]

Technical support specialists are av ailable between 8:00 A.M. and 5:00 P.M.
PST, Monday through Friday. Recorded technical information for selected
Seagate products is accessible 24 hours a day, 7 days a week.

SeaTDD: [phone]

TDD is a telecommunication device for the deaf where two people can
communicate using a keyboard connected to the phone line. A TDD device is
required to access this service, which is available from 8:00 A.M. to 5:00 P.M.
PST, Monday through Friday.

SeaBOARD:

The Seagate Technical Support Bulletin Board System (BBS) is available 24
hours a day, 7 days a week. A modem is required to access this service. The
communications software must be set for 8 data bits, no parity, and 1 stop bit
(8N1). All BBS numbers operate at 9600 baud max. With this service you can
access:

• Specifications and jumper configurations for Seagate products

• Reprints of Seagate documentation

• A directory of information and helpful utilities that you can download to your

own computer

x ST43401N/ND, ST43402ND User’s Manual, Rev. B

Telephone

Location number

USA, Mexico, Latin America [phone]
England 44-62-847-8011
Germany 49-89-140-9331
Singapore 65-292-6973
Australia 61-2-756-2359
Canada [phone]
France 33-1-40-67-1034
Korea 82-2-556-7294

ST43401N/ND, ST43402ND User’s Manual, Rev. B 1

Section 1. General description

Seagate ST43401N/ND and ST43402ND Elite 3 disc drives are high speed,
random access digital data storage devices. They communicate with an
initiator using the fast and wide (16-bit) Small Computer System Interface
(SCSI-2). The ST43401N/ND disc drive is shown in Figure 1, and the
ST43402ND (dual port) disc drive is shown in Figure 2. Specifications for
these drives are listed in Table 1 following the figures.

The drive is a component for installation in an enclosure designed for the drive.
The enclosure design must ensure adequate cooling for the drive, and it must
address the requirements for grounding and for shielding of emissions. The
reference manual (publication 83327730) presents guidelines for a properly
designed enclosure.

Option Jumpers and

Spindle Sync

Connector

Option

Jumpers

Option

Jumpers

Pin 1

I/O

Connector

Head and Disc

Assembly (HDA)

DC Power
Connector

Figure 1. ST43401N/ND disc drives

Control

Board

Option

Jumpers

Power

Board

Optional

Bezel

Chassis

2 ST43401N/ND, ST43402ND User’s Manual, Rev. B

Control

Board

Spindle Sync

Remote Operator

Panel Connector

Port B

I/O Connector

Port B

Terminator

Power

Terminator

Figure 2. The ST43402ND disc drive

Connector

Option

Jumpers

Port A
Power

I/O Board

Power

I/O

Board

DC Power

Pin 1

Connector

Port A

I/O Connector

Option

Jumpers

Power

Board

Head and Disc

Assembly (HDA)

Optional

Bezel

Chassis

ST43401N/ND, ST43402ND User’s Manual, Rev. B 3

Table 1. Drive specifications
Characteristics Conditions Specifications

Size Dimensions See “Space requirements”

in Section 2

Weight (drive only) 3.6 kg (8.0 lb)
Interface Fast and wide (16-bit) SCSI-2
Recording Total capacity (unformatted) 3,554,871,600 bytes

Bytes per track (unformatted)

Inner track 49,000 bytes
Outer track 72,800 bytes

Formatted capacity*

(256-byte sectors) 2,536,189,440 bytes
(512-byte sectors) 2,912,484,864 bytes

(1,024-byte sectors) 3,142,281,216 bytes
Number of discs 11
Recording heads 21
Servo heads 1
Physical heads per surface 1
Cylinders per head/disc assy 2,738
Cylinders available to user 2,735
Spare cylinders 1 (default/programmable)
System cylinders 1
Diagnostic cylinders 1
Spare sectors per cylinder 9 (default/programmable)
Modulation RLL 1,7 code

* Excluding spare sectors, spare cylinders, diagnostic cylinders, and

system cylinders.

continued

4 ST43401N/ND, ST43402ND User’s Manual, Rev. B

continued from previous page

Characteristics Conditions Specifications

SCSI transfer rate, burst 20.0 Mbytes/sec max
Seek time (time required Typical full 23.5 msec

to move heads to a different Typical average 11.5 msec
track address—excluding Typical one-track 1.7 msec
SCSI I/O overhead)

Typical access times Write Read

msec msec

Single track seek 1.7 0.9
Average seek 11.5 10.5
Maximum seek 23.5 22.5

Latency (time required Average 5.55 msec
to reach a particular (disc rotation
track address after head at 5,400 RPM)
positioning is complete)

Maximum 11.17 msec
(disc rotation

at 5,373 RPM)
Start time** 30 sec max
Stop time 30 sec max

** Following the power sequence delay, once DC power is applied and

start conditions are present.

ST43401N/ND, ST43402ND User’s Manual, Rev. B 5

The drive contains all the circuits and mechanical devices necessary to record
data on and recover it from its discs. The drive requires DC voltage inputs from
an external power supply, which you must supply. The DC power cable is
available as an accessory.

The ST43401N/ND drives consist of a head and disc assembly (HDA) with two
circuit boards, and the ST43402ND drive consists of an HDA and three circuit
boards. Each drive’s HDA and circuit boards are mounted on a common
chassis. The circuit boards contain the electronics required for drive opera­tion. The HDA is a sealed unit containing the electromechanical components
used for data retrieval and storage . These components include the discs,
spindle, drive motor, actuator, heads, and preamplifiers.

The eleven discs provide the recording medium for the drive. These discs are
mounted on a spindle, and the spindle is coupled directly to the drive motor.
The drive motor rotates the discs at 5,400 RPM and produces a circulation of
air within the sealed HDA.

The built-in SCSI controller directs all drive functions, receives commands
from the initiator (host computer), interprets them, and then transfers the
necessary commands to the drive. The controller therefore allows the initiator
to start an operation and then disconnect to service another device. Refer to
the reference manual for a description of interface functions.

All drive operations are related to data recovery and storage (normally
referred to as reading and writing). The actual reading and writing is performed
by heads that are positioned over the rotating discs’ recording surfaces. There
is one head for each data surface. The heads are positioned in such a way that
data is written in concentric tracks around the disc surfaces (see Figure 3).

Before any read or write operation can be performed, the controller must
instruct the drive to position the heads over the desired cylinder (called
seeking) and use the head located over the surface (head selection) where the
operation is to be performed.

The heads are mounted on the actuator, and the actuator moves the heads
over the rotating discs. There are 22 heads—a servo head to sense actuator
positioning, and 21 data heads used for data transfers to and from the discs.
The actuator has a voice coil that moves in a permanent magnetic field in
response to signals from the servo positioning circuitry. The voice coil moves
the heads in an arc across the rotating discs.

6 ST43401N/ND, ST43402ND User’s Manual, Rev. B

When the drive is not powered on, the heads rest on the disc surface in a
preassigned landing zone beyond the data zone. The actuator automatically
latches in this position at shutdown for moving or shipping protection. When
the drive is activated to bring the discs up to speed, the heads fly on a cushion
of air close to the disc surface.

After arriving at the data track and selecting a head, the controller locates the
portion of the track where the data is to be read or written. This is called track
orientation. Signals from the drive indicate the beginning of each track. The
controller uses these signals to determine the position of the head on the track.

When the head is above the desired track location, the controller commands
the drive to actually read or write the data. During a read operation, the drive
retrieves data from the discs, processes it, and transmits it to the controller.
During a write operation, the drive receives data from the controller, processes
it, and stores it on the discs.

The drive can recognize certain errors that may occur during its operation.
When an error is detected, it is indicated to the initiator by the SCSI controller.

Unit

Selection

Logic

SCSI

Initiator

Controller

I/0 Lines

Read/Write

Logic

Seek
Logic

Track

Orientation

Logic

Error

Detection

Logic

Figure 3. Drive functional block diagram

Data recorded in
concentric tracks

Head

Selection

Logic

Heads

Discs

Power Supply

ST43401N/ND, ST43402ND User’s Manual, Rev. B 7

Section 2. Installation/Abschnitt 2. Installation

The information contained in this section describes installation and initial
checkout of the drive.

Site requirements

The site requirements considered are environment, airflow, space, power,
grounding, and interface.

Voraussetzungen am Aufstellungsort

Zu den Voraussetzungen am Aufstellungsort gehören Umgebung,
Luftfluß, Raum, Strombedingungen, Erdung und Schnittstelle.

Environmental requirements

All environmental requirements for the drive are listed in Table 2.

Umgebungsbedingungen

Alle Umgebungbedingungen für das Laufwerk sind in der
nachstehenden Tabelle 2 aufgelistet.

8 ST43401N/ND, ST43402ND User’s Manual, Rev. B

Table 2. Environmental requirements
Conditions Specifications

Operating environment

Temperature Range of 5°C to 50°C (41°F to 122°F) with a

maximum change of 20°C (36°F) per hour

Humidity Range of 5% to 95% relative

A maximum wet bulb temperature of 26°C (79°F)

Barometric pressure

Non-operating environment (unpacked)

Temperature Range of –40°C to 60°C (–40°F to 140°F) with a

Humidity Range of 5% to 95% relative

Barometric pressure

Transit and storage environment (packed)

Temperature Range of

Humidity Range of 5% to 95% relative
Barometric pressure

– 305 m to 3,048 m (– 1,000 ft to 10,000 ft)

104 kPa to 69 kPa (30 in Hg to 20 in Hg)

maximum change of 20°C (36°F) per hour

A maximum wet bulb temperature of 26°C (79°F)

– 305 m to 12,192 m (–1,000 ft to 40,000 ft)

104 kPa to 19 kPa (30 in Hg to 6 in Hg)

–40°C to 60°C (– 40°F to 140°F) with a

maximum change of 20°C (36°F) per hour

– 305 m to 12,192 m (–1,000 ft to 40,000 ft)

104 kPa to 19 kPa (30 in Hg to 6 in Hg)

ST43401N/ND, ST43402ND User’s Manual, Rev. B 9

Tabelle 2. Umgebungsbedingungen des Laufwerkes
Bedingungen Technische Daten

Betriebsumgebung

Temperatur 5°C bis 50°C mit einer maximalen

Schwankung von 20°C pro Stunde

Relative Luftfeuchtigkeit 5% bis 95%

Maximale Naßthermometertemperatur
von 26°C

Luftdruck

–305 m bis 3.048 m; 104 kPa bis 69 kPa

Umgebungsbedingungen bei Nichtbetrieb (unverpackt)

Temperatur

– 40°C bis 60°C mit einer maximalen

Schwankung von 20°C pro Stunde

Relative Luftfeuchtigkeit 5% bis 95%

Maximale Naßthermometertemperatur
von 26°C

Luftdruck

–305 m bis 12.192 m; 104 kPa bis 19 kPa

Lager-/Transportbedingungen (verpackt)

Temperatur –40°C bis 60°C mit einer maximalen

Schwankung von 20°C pro Stunde
Relative Luftfeuchtigkeit 5% bis 95%
Luftdruck

–305 m bis 12.192 m; 104 kPa bis 19 kPa

10 ST43401N/ND, ST43402ND User’s Manual, Rev. B

Air-flow requirements

The enclosure design must ensure adequate cooling for the drive. Note that
the fan in the power supply cools only the power supply’s internal parts.

The drive’s product specification (document 64403603) describes how to
evaluate the air-flow design. The evaluation consists of ensuring that the case
temperatures of certain critical components remain within acceptable limits
during drive operation.

We recommend orienting the drive or directing the air flow in a way that
creates the least amount of air-flow resistance while providing air flow
above the circuit boards and around the head and disc assembly (HDA).
Also, choose the shortest possible path between the air inlet and exit. This
minimizes the distance traveled by air that is heated by the drive and by
other nearby heat sources.

Figure 4 shows two design approaches with one or more fans used to
generate airflow. The air-flow patterns can be created by the fans either
pushing or drawing air. The overall flow pattern can be directed from front to
back, back to front, or side to side.