Seagate ST425 User manual

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Manhattan House
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Berkshire SL6 8DB
Telephone:
Maidenhead
(0628) 75851
Telex:
847898 MANSKY
Facsimile:
[phone]

•
ST425 WINCHESTER DISC DRIVE
SERVICE MANUAL
June 28, 1984
Manhatt.n ~
Bridge Road
Maidenhead
BerkshireSL6 808
•
- J
Seagate. 920 Disc Drive. Scotts Valley,CA95066 • [phone]

•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 •••
·.
·.
I

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
•27
•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
J
II

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).
1

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)
G (peak)
double amplitude
double amplitude
G (peak)
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)
2

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
inches
inches
pounds
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
3

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
8
2
4

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.
5
..