Seagate ST43401N/ND User manual

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Elite Disc Drive
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ST43401N/ND
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ST43402ND
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User’s Manual
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© 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.
Contents
Preface ................................................................................................... iii
Electrostatic discharge protection....................................................... iii
Important safety information and precautions..................................... iv
WichtigeSicherheitshinweise ......................................................... 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

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 informationis availablein thereference manual(publication
83327730).
Electrostatic discharge protection
Caution. Removalofcircuitboardsbypersonnelnotperformingdepotrepair
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
dischargeofachargedconductor,orbyexposuretothestaticfieldssurround-
ingchargedobjects.Toavoiddamagingdriveelectronicassemblies,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.
Usepropersafetyandrepairtechniquesforsafe,reliableoperationofthisunit.
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
cautionsthatmustbecarefullyreadandfollowedtominimizeoreliminatethe
riskofpersonalinjury.Thewarningspointoutconditionsorpracticesthatmay
endanger you or others. The cautions point out conditions or practices that
may damage the unit, possibly making it unsafe for use.
Youmustalsounderstandthat these warnings andcautionsarenotexhaus-
tive. We cannot possibly know, evaluate, and advise you of all the ways in
whichmaintenancemightbeperformedorthepossibleriskofeachtechnique.
Consequently,wehave not completedanysuchbroad evaluation.Ifyouuse
anon-approvedprocedureortool,firstensurethatthemethodyouchoosewill
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.
• Usecautionwhentroubleshootingaunitthathasvoltagespresent.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
boardsbypersonnelnot performing depotrepairwilldamagecomponents
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.
• DonotattempttodisassembletheHDA.Itisnotfieldrepairable.Ifthesealed
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
accordancewithUL1950,IEC950,EN60950,CSAC22.2950,andVDE0805.
• Ensure that the power supply meets the specifications in this manual and
isdesignedtobeusedinaccordancewithUL1950,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 condi-
tionally certify component assemblies, such as the Elite disc drive, based on
theirfinalacceptabilityintheend-useproduct.Thesubsystemdesignersare
responsible for meeting these conditions of acceptability in obtaining safety/
regulatory agency compliance in their end-use products and in certifying
whererequiredbylaw.Anecessarypartofmeetingsafetyrequirementsisthe
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,zuverlässigenBetriebdieserEinheitzugewährleisten.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.
DieVerfahrenindiesemHandbuchunddieAufkleberaufdemGerätenthalten
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,diedieEinheitbeschädigenkönnen,sodaßderenGebrauchmit
Risiko behaftet ist.
DieWarn-undVorsichtshinweisesind nichtallumfassend!Es istunseinfach
nicht möglich, alle Wartungsmethoden oder die eventuellen Risiken jeder
Methode zu kennen, zu beurteilen und Sie entsprechend zu beraten. Aus
diesemGrundhabenwiraufeinederartigeumfassendeBeurteilungverzichtet.
FallsSieeinhiernichtbeschriebenesVerfahrenoderWerkzeug verwenden,
stellenSiezuerstsicher,daßdasgewählteVerfahrenwederIhrepersönliche
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.
• TreffenSiebeimBetrieboderbeiderReparatur der Einheit angemessene
Sicherheitsvorkehrungen.
• WenneineEinheitunterSpannungsteht,gehenSiebeiderFehlerdiagnose
besonders vorsichtig vor. Schalten Sie die Einheit aus, bevor Sie mit den
Reparaturarbeitenbeginnen.

ST43401N/ND, ST43402ND User’s Manual, Rev. B vii
• TragenSieSicherheitsschuhe,wennSieschwereTeileaus-bzw.einbauen.
• Wenn das Laufwerk in einem Einbaugestell oder Gehäuse montiert ist,
sorgen Sie dafür, daß die Temperatur im Inneren des Gestells oder
GehäusesdiefürdasLaufwerkvorgegebenenGrenzwertenichtübersteigt.
Wenn Einheiten vertikal gestapelt werden, achten Sie besonders auf den
oberenStapelbereich,dadortdieTemperaturgewöhnlichamhöchstenist.
• Befolgen Sie die oben unter “Electrostatic Discharge Protection”
angegebenenSicherheitsmaßnahmen.
• NehmenSiekeinePlatinenausdemLaufwerkgehäuse.WenneinePlatine
defektist,mußdasgesamteLaufwerkzurReparatureingeschicktwerden.
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
Laufwerkgehäusenehmen!FallsdieHDAbeschädigtist,schickenSiedas
gesamte Laufwerk zur Reparatur ein.
• DieHDAistnichtvorOrtreparierbarunddarfnichtauseinandergenommen
werden!ÖffnenderversiegeltenHDAdurchanderePersonenalsdiefürdie
werkseitigeReparaturzuständigenhateineBeschädigungderKomponenten
und Erlöschen des Garantieanspruchs zur Folge.
• AlsTeilkomponenteistdiesesLaufwerkfürdieInstallationunddenBetrieb
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
HandbuchentsprichtundfürdenBetriebinÜbereinstimmungmitUL1950,
IEC950, EN 60950, CSA C22.2 950 und VD0805 vorgesehen ist.
Seagateistständigbemüht,dieZulassungsfähigkeitvonSeagate-Produkten
im Rahmen der gegenwärtig geltenden Standards zu gewährleisten. Zu den
typischenAnwendungendieserFestplattenwerkezählenSystemeinbaudurch
denKundenunddieKonstruktionvonUntersystemen.Sicherheitsbehörden
gewähren eine bedingte Zulassung für Komponenten wie das Elite-
FestplattenlaufwerkvorbehaltlichderendgültigenZulasssungimEndprodukt.
DesignervonUntersystemensinddafürverantwortlich,dieVoraussetzungen
für die Einhaltung sicherheits- oder aufsichtsbehördlicher Vorschriften in
ihrenEndproduktenund -fallsgesetzlich vorgeschrieben-für dieZulassung
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
AnforderungenderFCCoderähnlichernationalerBehördenfüreigenständige.
Technische Testergebnisse zu Frequenz- und Elektrizitätsemissionen sind
für Designer von Untersystemen auf Anfrage von der Seagate-
Sicherheitsabteilungerhältlich.

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 avail-
able 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
Useatouch-tonetelephonetoaccessSeagate’sautomatedFAXsystemand
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 available 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
communicateusingakeyboardconnectedtothephoneline.ATDDdeviceis
required to access this service, which is available from 8:00A.M. to 5:00P.M.
PST, Monday through Friday.
SeaBOARD:
TheSeagateTechnical SupportBulletinBoard System(BBS)isavailable24
hoursaday,7 days aweek.Amodemis required toaccessthisservice.The
communicationssoftwaremust besetfor 8databits,noparity,and1 stopbit
(8N1).AllBBSnumbersoperateat9600baudmax.Withthisserviceyoucan
access:
• Specifications and jumper configurations for Seagate products
• Reprints of Seagate documentation
• Adirectoryofinformationand helpfulutilitiesthat youcandownloadtoyour
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

Control
Board Power
Board
Optional
Bezel
Chassis
DC Power
Connector
Option Jumpers and
Spindle Sync
Connector
Option
Jumpers
I/O
Connector
Option
Jumpers
Option
Jumpers
Head and Disc
Assembly (HDA)
Pin 1
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.
Thedriveisacomponentforinstallationinanenclosuredesignedforthedrive.
Theenclosuredesignmustensureadequatecoolingforthedrive,anditmust
address the requirements for grounding and for shielding of emissions. The
reference manual (publication 83327730) presents guidelines for a properly
designed enclosure.
Figure 1. ST43401N/ND disc drives

2 ST43401N/ND, ST43402ND User’s Manual, Rev. B
Control
Board
Chassis
Head and Disc
Assembly (HDA)
Power
Board
DC Power
Connector
Option
Jumpers
Pin 1
I/O
Board
Optional
Bezel
Spindle Sync
Connector
Remote Operator
Panel Connector
Port B
I/O Connector
Port A
I/O Connector
Port A
Terminator
Power
Port B
Terminator
Power Option
Jumpers
I/O Board
Power
Figure 2. The ST43402ND disc drive

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) 3,554,871,600bytes
Bytes per track (unformatted)
Inner track 49,000 bytes
Outer track 72,800 bytes
Formatted capacity*
(256-byte sectors) 2,536,189,440bytes
(512-byte sectors) 2,912,484,864bytes
(1,024-byte sectors) 3,142,281,216bytes
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
Thedrivecontainsallthecircuitsandmechanicaldevicesnecessarytorecord
dataonandrecoveritfromitsdiscs.ThedriverequiresDCvoltageinputsfrom
an external power supply, which you must supply. The DC power cable is
available as an accessory.
TheST43401N/NDdrivesconsistofaheadanddiscassembly(HDA)withtwo
circuitboards,andtheST43402NDdriveconsistsofanHDAandthreecircuit
boards. Each drive’s HDA and circuit boards are mounted on a common
chassis. The circuit boards contain the electronics required for drive opera-
tion.TheHDAisasealedunitcontainingthe electromechanicalcomponents
used for data retrieval and storage . These components include the discs,
spindle, drive motor, actuator, heads, and preamplifiers.
Theelevendiscsprovidetherecordingmediumforthedrive.Thesediscsare
mounted on a spindle, and the spindle is coupled directly to the drive motor.
Thedrivemotorrotatesthediscsat 5,400RPMandproducesa circulationof
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
necessarycommandstothedrive.Thecontrollerthereforeallowstheinitiator
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
referredtoasreadingandwriting).Theactualreadingandwritingisperformed
byheadsthatarepositionedovertherotatingdiscs’recordingsurfaces.There
isoneheadforeachdatasurface.Theheadsarepositionedinsuchawaythat
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)andusetheheadlocatedoverthesurface(headselection)wherethe
operation is to be performed.
The heads are mounted on the actuator, and the actuator moves the heads
overtherotatingdiscs. There are22heads—aservohead to senseactuator
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
responsetosignalsfromtheservopositioningcircuitry.Thevoicecoilmoves
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
preassignedlandingzonebeyondthedatazone.The actuator automatically
latches in this position at shutdown for moving or shipping protection. When
thedriveisactivatedtobringthediscsuptospeed,theheadsflyonacushion
of air close to the disc surface.
Afterarrivingatthedatatrackandselectingahead,the controllerlocates the
portionofthetrack wherethedatais to bereadorwritten. Thisiscalledtrack
orientation. Signals from the drive indicate the beginning of each track. The
controllerusesthesesignalstodeterminethepositionoftheheadonthetrack.
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.
Duringawriteoperation,thedrivereceivesdatafromthecontroller,processes
it, and stores it on the discs.
The drive can recognize certain errors that may occur during its operation.
Whenanerrorisdetected,itisindicatedtotheinitiatorbytheSCSIcontroller.
Initiator
Unit
Selection
Logic
Read/Write
Logic
Head
Selection
Logic
Seek
Logic
Track
Orientation
Logic
Error
Detection
Logic
I/0 Lines
SCSI
Controller
Power Supply
Discs
Heads
Data recorded in
concentric tracks
Figure 3. Drive functional block diagram

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 –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)
Non-operating environment (unpacked)
Temperature Range of –40°C to 60°C (–40°F to 140°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 –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)
Transit and storage environment (packed)
Temperature Range of –40°C to 60°C (–40°F to 140°F) with a
maximum change of 20°C (36°F) per hour
Humidity Range of 5% to 95% relative
Barometric pressure –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
evaluatetheair-flowdesign.Theevaluationconsistsofensuringthatthecase
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,choosetheshortestpossiblepathbetweentheairinletandexit.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.