Seagate ST425 User manual

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Manhattan House

Bridge Road

Maidenhead

Berkshire SL6 8DB

Telephone:

Maidenhead

(0628) 75851

Telex:

847898 MANSKY

Facsimile:

(0628) 782812

•

ST425 WINCHESTER DISC DRIVE

SERVICE MANUAL

June 28, 1984

Manhatt.n ~

Bridge Road

Maidenhead

BerkshireSL6 808

•

- J

Seagate. 920 Disc Drive. Scotts Valley,CA95066 • (408)438-6550

•TABLE OF CONTENTS

SECTION

..............

PAGE

•1

l.e INTRODUCTION •• ·.~.

1.1 Specification Summary •••••••••••••••••••••••••• 2

1.1.1 Physical Specifications •••••••••••••••••• 2

1.1.2 Reliability Specifications ••••••••••••••• 3

1.1.3 Performance Specifications ••••••••••••••• 4

1.1.4 Functional Specifications •••••••••••••••• 4

2.e THEORY OF OPERATIONS ••••••••••••••••••••••••••••••• 5

2.1.3 Read/Write Heads •.••••••••••••••••••••••• 8

For mat... 0 ••••••••••••••••••••••••• 7

.............

Interface Description • ••5-6

•7·.

2.1.1 Recording Format ••

2.1.2 Track

2.1 General

•

2 •1 •4 DiBe s ••••••••••..••••••••••••••••••••••••• 8

2.1.5 Air Filtration System •••••••••••••••••••• 8

2.2 Mechanical Theory •.••••••••••••••.••••••••••••• 9

2.2.1 Track 0 Sensor .....•.•...•..........•••.. 9

2.2.2 Index Sensor ••...•..•..••••.....•..•..... 9

2.2.3 Ground Spring ••••• ·.• • • 9

2.3 Electrical Theory ••••••••••••••••••••••

2.3.1 Main Control PC Board 2e321-eel •

•le-18

.... le

2.3.2 Microprocessor Operation ••••••••••••• 11-12

2.3.3 Drive Select •••••••••••••••••••••••••••• 13

•14-15

•16-17

2.3.4 Read Operation ••••

2.3.5 Write Operation •••

·.

2.3.6 Fault Detection ••••••••••••••••• ..... 18

2.4 Test Point Data - PC Board 20321-001 •••••.• 19-21

•••••22

- Index •••••••••

2.5 Schematics

3.0 FIELD SERVICE AND ADJUSTMENTS •

..............

................•25-32

3.1 Removals and Adjustments •••••••••••••••••••••• 26

3.1.1 Main Control PCB ••••••••••.•.••••••••••• 26

......................

·.

Front Cover LED •••

.26

•28

•27

.....................

·.

Cover ••••••

Frame ...•.••••••

Front

Ground Spring ••

Index Sensor •••3.1.2

3.1.3

3.1.4

3.1.5

3.1.6

3.1.7 Track oSensor ••• •28

4.0 ILLUSTRATED PARTS CATALOG - INDEX. •• 29

·.

..................... ••• 30

•••32

••• 31

..........

Component Locations ••••••••••••••

Interface Connectors ••

Exploded View •••.••••

4.1

4.2

4.3

4.4 Parts List - PC Board 20321-001 •••••••••••• 33-34

5.0 FIELD SALES OFFICES •.••••••••••••••••••••••••••••• 35

ILLUSTRATIONS

FIGURE PAGE

1.0 Test Point Layout - PC Board 20321-001 •••••••••••• 20

2.0 Test Point Timing - PC Board 20321-001 •••••••••••• 21

3.0 Interface Connectors •••••••••••••••••••••••••••••• 30

4.~ Exploded View ......•..............•..•.•........•. 31

5.0 Component Locations PC Board 20321-001 •••••••••••• 34

III

1.8 INTRODUCTION

The ST425 is Seagate's 25.52 Megabyte, 5 1/4 inch

Winchester disc drive. The ST425 has a formatted

capacity of 20.0 Megabytes.

The ST425 is the newest addition to the ST400 family of

disc drives, and has the same interface, power supply

and controller requirements as the industry standard

Seagate ST406/412/419 series.

Minislider heads and an advanced stepper motor design

enable higher track density. The new head design allows

increased bit packing which utilizes more of the disc

surface. High reliability is assured through the use of

Seagate's proven metal band-actuator, stepper motor head

positioner and a direct-drive brushless DC spindle

motor. The spindle motor assembly is aynamically

balanced and the Head Disc Assembly (HDA) is shock-

mounted to reduce vibration.

The low mass/load force of the MiniWinchester heads and

the lubricated oxide coated media provide reliable

start/stop operation. Each disc surface is read by two

read/write heads. The HDA, which includes the read/write

heads, discs and band-actuator assembly, is completely

sealed and protected by a captured-air-space

recirculation system employing a 0.3 micron absolute

filter. A filtered port permits ambient air pressure

equalization.

Thermal stabilization delays are unnecessary with the

ST425. The spindle pump assures adequate air flow and

uniform temperature distribution throughout the HDA.

This allows significantly greater off-track margin and

immediate read/write ability after power-up.

Only DC voltages (+5 and +12 V DC) are required. All

electronics are packaged a single printed circuit board.

The board is mounted outside the sealed media area

allowing easy field access without risking media

integrity. Simplification of mechanical and electrical

design provides a projected service life of more than

11,000 hours Mean Time Between Failures (MTBF).

5~o to 1130F (l~O to 450C)

-4eo to 14~oF (-4eo to 6eoC)

1.1 SPECIFICATION SUMMARY

1.1.1 Physical Specifications

Environmental Limits

Ambient Temperature Limits

Operating:

Non-Operating:

Maximum Temperature Gradient

Operating: 18oF/hour (l~oC/hour)

Non-Operating: Below Condensation

•

Relative Humidity:

Maximum Wet Bulb:

Maximum Elevation

Operating:

Non-Operating:

8 to 8e% non-condensing

78.8oF (260C)

-l,~ee feet to le,e~e feet

-l,~~~ feet to 3~,~~0 feet

Maximum Shock Without Incurring Physical Damage

[11 msec shock pulse, half sine wave]

Operating:

Longitudinal:

Lateral:

Vertical:

Non-Operating:

No mechanical damage

specified limits.

3GiS

5GiS

7GiS

35 GiS

will occur within the above

•

Without Incurring Soft Errors:

Incurring Physical Damage.

Maximum Vibration

Operating:

Frequency

2--22 Hz

22-5ee Hz

5~e--22 Hz

22---2 Hz

Maximum Vibration Without

Non-operating:

Frequency

2--22 Hz

22-5~~ Hz

5~~--22 Hz

22--2 Hz

.~10"

~.25

0.25

.01~"

.~4~"

l.~

1.0

.e40"

double amplitude

G (peak)

double amplitude

G (peak)

double amplitude

DC Power Requirements

+12 Volts +5%

+5 Volts ±5

Maximum Ripple:

1.6 A Typ., 3.5 A (at power-on)

1.1 A Typ., 1.7 A (Max.)

5e mV peak to peak (12 V, 5 V)

Heat Dissipation

Typical:

Maximum: 25 Watts

29 Watts

Mechanical Dimensions

Height:

Width:

Depth:

Weight:

Shipping Weight:

3.26

5.75

8.00

4.6

7.0

inches

pounds

Maximum

[2.1 Kg]

[3.2 Kg]

1.1.2 Reliability Specifications

MTBF:

MTTR:

PM:

The component design life

11,000 POH @250C Typ. usagt

30 minutes

Not required

is 5 years.

Read error Rates (Based on bit-jitter reduction)

Soft Read Errors :

Hard Read Errors :

Seek Errors:

1 per 1010 bits read

1 per 1012 bits read

1 per 106 seeks

Bit-jitter reduction determines the relationship between

the leading edge of read data and the center of the data

window. The data separator must provide at least -40 dB

of bit-jitter reduction at 2F with an offset error of

1.5 nsec shift from the center of the data window.

:*Recoverable within 16 retries

Not recoverable within 16 retries

1.1.3 Performance Specifications

CAPACITY

Per Drive:

Per Surface:

Per Track:

Access Time:

FORMATTED

20.0 MB

5.0 MB

8,192 Bytes

UNFORMATTED

25.52 MB

6.38 MB

10,416 Bytes

Seek Times Including Settling

Single Track: 19.67 msec

Buffered Seek (from last Step pulse to SEEK COMPLETE)

Average Seek: 65 msec

Full Seek: 140 msec

Transfer Rate:

Average Latency: 5.0 MBits/sec

8.33 msec

1.1.4 Functional Specifications

Rotational Speed:

Recording Density:

Flux Density:

Track Density:

Cylinders:

Tracks:

Read/Write Heads:

Discs:

3,600 RPM ±l%

10,568 Bits per inch (Maximum)

10,568 Flux changes per inch (Maximum)

550 Tracks per inch

306

2,448

2.0 THEORY OF OPERATIONS

2.1 General Interface Description

The ST425 Winchester supports the Seagate ST506/412

Interface.

The interface consists of a 34 pin control connector, a

20 pin read/write connector and a 4 pin DC connector.

The 34 pin connector provides 10 control signals to the

drive and returns 5 status signals to the controller.

The 20 pin connector handles the Modified Frequency

Modulation (MFM) data to/from the drive and supplies the

drive-selected status to the controller. The 4 pin

connector provides +5 and +12 Volts DC.

In general, the control connector is "daisy-chain"

terminated throughout the user system, while the

read/write connector is terminated radially. The

following tables indicate the ST425 interface

requir'ements.

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