Seagate ST-506 User manual

SEAGATE ThCHNOLOGY
ST-506 MICROWINCHESfER
SERVICE MANUAL
MAY 1, 1982
360 El Pueblo Road Scotts Valley, CA 95066 Phone[phone]

TABLE CF <XNIENTS
SEO]CN
1.0
I~~Irn .................................................. •• 1
1.1
1.2
General Description ••••••••••••••••••••••• ~ •••••••••••••• 1
Specification Sunnary •••••••••••••••••••••••••••••••••••• 2
1.2 •1Phy sic al •• "" """ eee '" .. '" '" .. '" '" '" 2
1.2.2 Reliability ••••••••••••••••••••••••••••••••••••••• 2
1.2 •3 Per formance ••••••••••••••••••••••••••••••••••••••• 3
1.2.4 Functional •••••••••••••••••••••••••••••••••.••••••• 3
2.0
~y G' CPERA.TICN'S •••••••••••••••••••••••••••••••••••••••••• 4
2.1 General •...•..••.•.•.••••...•.•......••...•...•.••.••.•.• 4
2.1.1 Recording Format •••••••••••••••••••••••••••••••••• 4
2
.1.2 Tr ack Format ••••••••••••••••••••••••••••••• " •••••• 4
2.1.3 Winchester Heads •••••••••••••••••••••••••••••••••• 6
2.1.4 Discs 6
2.1.5
Air Filtration Systern ••••••••••••••••••••••••••••• 6
2.2 Mechanical Theory •••••••••••••••••••••••••••••••••••••••• 7
2.1.1 Track ~ Sensor •••••••••••••••••••••••••••••••••••.• 7
2.2.2
2.2.3
2.2.4
Index Sensor •••••••••••••••••••••••••••••••••••••• 7
Ground
Spr ing ••••••••••••••••••••••••••••••••••••• 7
Spindle Brake .......•....•.......................• 8
2.3
Electrical Theory/Flowchart •••••••••••••••••••••••••••••• 9
2.3.1 Motor Speed Control ••••••••••••••••••••••••••••••• 9
2.3.2 Auto Recalibration ••••••••••••••••••••••••••••••• 11
2.3.3 Drive Selection •••••••.•••••••••••••••••••••••••• 13

SEO]CN
TABLE CE a:NIENTS
2.3.4
2.3.5
Step (peration ••••••••••••••••••••••••••••••••••• 14
Read
Cperation ••••••••••••••••••••••••••••••••••• 17
2.3.6 Write Cperation •••••••••••••••••••••••••••••••••• 19
2.4 Test Point Description ••••••••••••••••••• , •••••••••••••• 22
2 • 5 Schana tic s••••••••••••••••••••••••••••••••••••••••••••••28
3. 0 ~I~<:E/REI>AIR ••••••••••••••••••••••••••••••••••••••••••• 34
3.1
3.2
Introduction •••••••••••••••••••••••••••••••••••••••••••• 34
Rexnovals And Adjusttnents •••••••••••••••••••••••••••••••• 35
3.2.1 Main Control P.C.B ••••••••••••••••••••••••••••••• 35
3.2.2 Motor Control P.C.B •••••••••••••••••••••••••••••• 35
3.2.3 Spindle Brake •••••••••••••••••••••••••••••••••••• 36
3.2.4 Index Sensor ••••••••••••••••••••••••••••••••••••• 36
3.2.5 Ground Spring •••••••••••••••••••••••••••••••••••• 37
3.2.6 Track ~ Sensor ••••••••••••••••••••••••••••••••••• 37
3 .2 •7 FrontCover •••••••••••••••••••••••••••••••••••••• 38
3.2.8
3.2.9
Front Cover LED •••••••••••••••••••••••••••••••••• 38
Side Franles •••••••••••••••••••••••••••••••••••••• 38
4.0
ILLUSTRATED PARTS CATALOG •••••••••••••••••••••••••••••••••••• 40
4.1
4.2
Physical Locations •••••••••••••••••••••••••••••••••••••• 40
4.1.1 Drive Exploded View •••••••••••••••••••••••••••••• 41
4.1.2 Connectors Exploded View ••••••••••••••••••••••••• 42
Carr~onent Locations ••••••••••••••••••••••••••••••••••••• 43
ii

SEO]CN
TABLE OF c:INIFNrS
4.2.1 Main COntrol p.e.B. PfiN 20019 ••••••••••••••••••• 44
4.2.2 Main COntrol P.C.B. PIN 20040 ••••••••••••••••••• 45
4.2.3 Motor Control P.C.B. P/;N 20003 •••••••••••••••••• 46
4.3.1
Main
Control
P .C.B.
PjN 20019
••••••••••••••••••• 48
4.3.2
Main Control
P .C.B.
PIN
20040 ••••••••••••••••••• 50
4.3.3
Motor
Control
P .C.B.
PIN 20003
•••••••••••••••••• 52
4.3.4
Spare Parts
List ••••••••••••••.•••••••••.•••••••• 53
iii

LIST CF ILllSTRATICNS
FIGlRE
2.1
Tt ack Format •••••••••••••••••••••••••••• ~ ••••••••••••••••••••• 5
2.2
Test
Point
1Tim.ing ••••••••••••••••• "- •••.••• eo •••••• ~ ~ •••••••• •• 24
2.3
Test
Point 2
Tilning •••••••••••••••••••••••••••••••••••••••••• 24
2.4
Test
Point
4Tim.ing
•••••••••••••••••••••••••••••••••••••••••• 24
2.5
Test
Point
5
Tilning •••••••••••••••••••••••••••••••••••••••••• 24
2.6
Test Point
7
and
8Tim.ing
•••••••••••••••••••••••••••• ' ••••• ••• 25
2.7 Test Point 11 and 13 Tilning •••••••••••••••••••••••••••••••••• 25
2.8 Tes t Point Layout
p.e.B. P~ 20019 •••••••••••••••••••••••• 26
2.9 Tes t Point Layout - P .C.B.
PIN 20040 •••••••••••••••••••••••• 27
LIST CF TABLES
TABLE ~
2.1 Step Pulse Encoding/Phase Sequencing ••••••••••••••••••••••••• 16
iv

Introduction
1.0 INTRODUcnON
1.1 General Description
ST-506 Service Manual
The ST-506 disc drive is a random access storage device with two
non-fcmovable 5 i/4 inch discs as storage media. Each disc surface
emplQYs one moveable head to service 153 data tracks. The total
formatted capacity of the four he ads and surf ac es is 5 meg abyt es (32
sectors per track, 256 bytes per sector, 612 tracks). Up to four drives
may be daisy chain connected in one system.
Low cost and unit reliability are achieved through the use of a band
actuator and open loop stepper head positioning mechanism. The inherent
simplicity of m.echanical construction and electronic controls allows
maintenance free operation throughout the life of the drive. Both
electronic PCB's are mounted outside the HDA for field serviceability.
Mechanical and contamination protection for the heads, actuator and discs
are provided by an impact resistant aluminum enclosure. A self contained
recirculating system supplies clean air through a 0.3 micron filter. A
second port in the filter assembly allows pressure equalization with
ambient air without chance of contamination. A patented spindle pump
aSSUf es adequate air flow and uniform temperature distribution throughout
the head and disc area. Therm.al isolation of the stepper and spindle
motor assemblies from the disc enclosure yields a very low temperature
rise within the enclosure, providing significantly greater off-tr ack margin
and the ability to immediately perform read and write operations after
power up with.nothermal stabilization delay.
The ST-506 electrical interface is similar to the Shugart Associates
SA1000 family of 8 inch fixed disc drives. The ST-506 size and mounting
ar e id en tic al to the industry standard minifloppy disc drives and uses the
same DC voltage and connector. No AC power is required.
Seagate Technology
PAGE 1
5/1/82

Introduction
1.2 Specification Summary
1.2.1 Physical Specifications
Environmental Lnnits
Sf-506 Service Manual
Ambient Temperature:
Ci>erating =
Non-operating =
Temperature Gradient:
Operating =
Non-operating =
ReI at ive HlIl1idi ty =
Maximun el evat ion:
Operating =
Non-operating =
Shock:
<»erating =
r-~on-opelati.ng :::
400 to 1220F (4
0
to 50
0
C)
-40
0
to 1400F (-40
0
to 60
0
C)
'180F / Hour (100 C)
Below condensation
8 to 80% Non-condensing
10,000 Feet
-1000 to 30,000 Feet
,lOG's (On side frames)
D.C. Power Requiranents:
+12V ±5%, 1.8A Typical,4.5A At power on
+5V ±5%" .7A Typical, 1.0A Maximum
Maximun Ripple = 50mv peak to peak (12V, 5V)
Mechanical Dimens ions:
Height =
Width =
Depth =
'¥eight =
Shipping Vleight =
Heat Dissipation:
Typical =
Maxinulm =
3.25 Inches
5.75 Inches
8.00 Inches
4.6 Pounds (2.1Kg)
7.0 Pounds (3.2Kg)
25 Watts
29 Watts
1.2.2 Reliability Specifications
NITBF = 11,000 PCH, Typical usage
MI1R = 30 Minutes
P,M: =Not required
Component design life =5 Years'
Seagate Technology
PAGE 2
5/1/82

Introduction Sf-506 Service Manual
Error Rates:
Soft Read Errors =
Hard Read Errors* =
Seek Error s=
1 per 10 10 bits read
1 per 1012 bits read
1 per 106 seeks
*Not recoverable within 16 retries
1.2.3 Perfonnance Specifications
Capaci ty
Unformat ted:
Per Drive =
Per Sur f ace =
Per Track =
Formatted:
Per Drive =
Per Surface =
Per Track =
Per Sector =
Sectors per Track =
AccessTime:
Track to Track =
Avera.ge* =
lv1ax imum **=
Set tl ing Time =
6.38 Megabytes
1 • 59 Meg aby t es
10416 Bytes
5 .0 Meg aby tes
1.25 Megabytes
8192 Bytes
256 Bytes
32
3 milliseconds
170 mill i seconds
500 milliseconds
15 milliseconds typical
*Reducible to 85 IDS using fast seek algorithm
*Reducible to 205 IDS using fast seek algorithm
Transfer Rate:.
Average Latency:
1.2.4 Functional Specifications:
5.0 Megabits per second
8.33 milliseconds
Rotational Speed =
Recording Density =
Flux Densi ty =
Track Density =
Cyl iode! s=
Tracks =
ReadfWrite Heads =
Di scs =
3600 RPM ±1%
7690 BPI Maximum
7690
FeI 1vlax imum
255 TIl
153
612
4
2
Seagate Technology
PAGE 3
5/1/82

Theory of Oper ations
2.0 THEORY OF OPERATIONS
2.1 General
2.1.1 Recording Format
ST-506 Servic e Manual
The ST-506 uses modified frequency modulation (MFM) as the encoding
method implemented to record data on the drive. This double-density
encoding scheme increases disc data capacity by replacing clock bits with
data bits. Clock bits are written only when data bits are not pr es ent in
both the preceding and the current bit cell. Clock bits are written at
the beginning of the bit cell, while data bi~s are written in the middle.
Due to predictable bit-shift- phenomena, write data may require
precompensatiori. This function must be provided by the controller to
insure data integrity at the specified error rate. The Sf-506 requires
precompensation of write data on cylinders 128 through 152. The data
pattern determines which bits must be precompensated. The recommended
amount of this precompensation is 12ns for both early and late written
bits. All other data patterns are written on time.
2.1.2 Track Format
The track format used on the Seagate ST-506 disc drive is a slightly
modified version of the IBM System 34 double density format. This
format is common to many industry standard floppy disc drives. All
ST-506 drives are formatted at the factory before shipping. Data fields
contain the bit pattern UJL Refer to Figure-2.1 (Track Format).
The Seagate soft-sector format divides each track into 32 sectors with
each containing 256 bytes of data. Total track capacity is 10416 bytes,
of which 8192 bytes are data." Each sector is identified by an
identification field that is different than any other on the drive. The ID
field contains cylinder, head, and sector information as well as address
m ark and error checking polynomials.
It should be noted that the format used by Seagate is recommended and
not required. Use of any other format requires careful evaluation, as the
format is an integral part of the drives' performance and operation. The
Seagate format uses Cyclic Redundancy Checking (eRC) for error
evaluation. The format also allows for a plus or minus speed variation of
3%. The ST-506 specification for spindle speed variation is 1% over the
specified environmental and power limits.
Seag ate Technology
PAGE 4
5/1/82

, __ rL __
FIGURIE 20
TRACK FORMAl· AS SHIPPED
INDEX ----fl ~
I
I
IRepeated
32 ,times (314 Bytes)
I
~
I Gap 1 ID Field -- -Gap 2- ---- Data Fie~d
SYNC eSC C
16X 4E 13XOO A 11 FE IrI ~ I ~ I ~ I ~ 3xOO 113xoo A 11 F81 256 Data
~ '--r
J
lOAM Data AM
GaIP
3
I
~I~
C C 3XOO f15X4E
Gap4
352X
4E
Nominal
-0
l>
C)
m
c.n
WRITE
UPDATE
NOTES: 1. Nominal Track Capacity = 10416 Bytes .
2. Total Data
Bytes/Track = 256 x 3~~ = 8,192
lL--' _
3. Sector interleave factor is 4. SequE!ntiallD Fields are sector numbered 0, B,
16,24, 1,9,17,25,2, 10, 18, 26, ... etc.
4. Data Fields contain
the bit pattern 0000 as shipped
5.
CRC Fire Code =X16+X12+X5+1
6. Bit 7 of Head Byte ID Field equals 1in adefective sector (Cylinder 0is orror free)
7.
Bit 5 of Head Byte reserved for nl.lmberingcylinders greate," than 256
8. Bit 6 of Head Byte reserved for nl.lmbering cylinders greater than 512

Theory of Operations
2.1.3 Winchester Heads
ST-506 Service Manual
The Seagate Technology ST-506 uses conventional Winchester head
technology. The head/flexture (supporting arm) assembly is designed for
contact start-stop operation. Bit packing density is 7690 BPI and the
radial track density is 255 TPI. The heads, when operational, are
supported on an ~1r bearing creat~d by the rotating disc.
The Winchester heads used are loaded toward the disc surface at 9.5
grams. This is the typical value to allow required stability in all
operating conditions. Tne flying height of the heads at the innermost
cylinder is 19 microinches with a tolerance of ±3 microinches
e
The flying
height of the heads at the outermost cylinder is 24 microinches, ±3
micrcinches.
The load force of 9.5 grams is sufficient enough so that various mounting
orientations of the disc drive will not affect the flying height of the
Winchester heads to any significant degree. Additionally, the
head/£lexture assembly incorporates an extremely low mass design that is
resistive to head and/or media damage when shipping.
2.1.4 Discs
The ST-506 disc drive uses two non-removable double sided 5 1/4 inch
discs as the recording media. The discs are designed upon curr ent iron
oxide technology. The actual disc dimensions are40mm inside diameter
by 130mm outside diameter. Thickness of the magnetic coating is 20 to
40 microinches increasing linearly from the inside diameter to the outside
diameter.
The disc surface is coated with a Teflon lubricant 40 to 60 angstroms in
thickness. This value is equivalent to a uniform monomolecular film.
The disc lubricant has sufficient abrasion resistance to withstand a
minimum
of 10,000 start/stop cycles. The magnetic discs have a life
expectancy of 5 years.
2.1.5 Air Filtration System
All drives manufactured by Sea&-ate Technology incorporate an integral air
filtration system. No maintenance or adj.ustments are needed throughout
the life of the drive. The integral 0.3 micron air filter performs two
functions. First, the filter maintains Class 100 standards inside the
seal ed He ad/D isc Assembly throughout the IiIe of the drive. Second, an
auxilIary port allows pressure equalization with ambient air. During
normal operation there is no measurable air flow between the HDA and
the outside environm ent.
Seag ate Teclmology PAGE 6
5/1/82

Theory of Op er ations
2.2 Mechar .. ical
2.2.1 Track tJ Sensor
ST-506 Service Manual
The Track ~ optical interrupter provides an output whenever the
Winchester heads are positioned over cylinder tJ. This signal is used by
the internal drive control electronics during the power-on auto-recalibrate
routine. The Track ~ signal is aiso output to the drive interface for use
by the controller. Note that the signal at the interfac e is really Track
fJ/Phase "A".
The Track tJ optical interrupter incorporates an infrared
light-emitting-diode and an infrared sensitive photo-transistor. When the
heads are positioned at cylinder J', an interrupter arm attached to the
stepper motor shaft mechanically breaks the light beam between the two
components of the sensor. The sensor will output a valid Track fJ signal
as long as the light beam remains broken.
2.2.2 Index Sensor
The Index sensor provides an index pulse to the recalibration circuit and
to the interface of the ST-506 drive. Once each revolution (16.67 ms),
the Index sensor outputs a pulse that is typically 200 microseconds in
width.
The Index sensor used on the ST-506 drive is of the reluctance
transducer type. This cylindrical sensor incorporates a built-in
preamplifier. The case of the sensor is grounded electrically which ties
the drive DC returns to the drive casting.
The hub of the spindle motor has two metal tabs attached; one is of a
ferrous composition and the other is non-magnetic. Each revolution of
the spindle motor causes the ferrous tab to pass within close proximity of
the Index sensor, therefore inducing the pulse output.
Note: The dimension between the spindle motor tab and the Index sensor
is set to 30 mils (.030'~ at the factory.
2.2.3 Ground Spring
The ST-506 incorporates a grounding contact between the spindle motor
hub and the drive casting. This ground spring performs the task of
removing all unwanted static electrical charges from the spindle motor
hub.
Seag ate Technology
PAGE 7
5/1/82

Theory of Oper ations
2.2.4 Spindle Br ake
ST-506 Service Manual
The ST-506 uses an electromechanical brake to slow the spindle motor
when 'DC power is removed. The spindle brake is energized directly from
the +12V supply. When +12V is removed from the drive, the brake
engages against the spindle motor hub to slow the motor.
.,
The pad contact material is of a rubber-cork composition with wear life
designed to exceed 20,000 cy,cles. When energized, the brake will draw a
maximum
current of 267 milliamps. '
The brake must be adjusted so that the contour of the pad contact
matches the spindle motor hub. When disengaged, the dimension between
the spindle motor hub and the pad contact should be set at 10 mils
(.0 IOU). "
Seagate Technology
PAGE 8 5/1/82

Theory of Operations
2.3 Electrical Theory/Flowchart
2.3.1 Motor Speed Control
Block Diagram-
ST-S06 Service Manual
III,1
CI:MPARAKR
HSfAR1ER HINIEGRA1rn
II I i
~
~L
C1.RRENT
SPINJLE
SFNSCB
CINIRa..
~DKR
III
Functional D escription-
Initially, when power is first applied, the disk is stationary and the Hall
effect transistor will output a high or low level, depending on the
physical position of the motor. This DC level will keep Ql turned off,
allowing CS to charge up. Pin 1 of Comparator A2 will output a low
level that travels through R12 and forces pin 7 of A2 high. As a result,
Al will be off and maximum current will flow into the coil selected by
the level ot" the Hall effect sensor.
As the motor speeds up, the Hall effect becomes a square wave
responsible for both selecting the motor coil to receive current and
controlling the amount of current applied. Current is supplied alternately
to coils A andB as the Hall device senses the motors physical position.
Depending on the time between high going edges of the Hall effect
sensor, Ql will be turned off long enough for CS to charge to mor ethan
4 volts and force pin 1 of Comparator A2 low. This low pulse will turn
on pin 7 of Al whose resulting 6 volt output pulse will direct pin 7 of
Integrator A2 to allow more current to enter the motor coils.
The sequence of normal operation is as follows:
1)
The Hall effect sensor relays speed and position information to the
speed error comparator and to the current controller.
2) The speed error comparator, pin 1 of A2, generates alow spike whose
duration is dependent on the speed error. A slow speed will result in
the low pulse being longer.
Seag ate Technology
PAGE 9
5/1/82

Theory of Oper ations ST-506 Servic eManual
3)
The speed error information enters the starting circuit which functions
to pass a low frequency signal directly to the integrator indic ating
maximum error during start up. The starting circuit also inverts the
speed error information and combines it with a carrier that properly
biases the integrator.
4) Pin 7 of Integrator A2 translates the error information into a level
appropriate for biasing both halves of Ie AI:; which functions to control
the current sourc e. -
5) The current control, IC A3, supplies the proper amount of current for
attaining proper speed as directed by IC AI.
Seagate Technology PAGE 10
5/1/82

Theory of Operations
2.3.2 Auto R ecalibration
Block Diagram-
ST-506 Servic eManual
512PlLSE
aINIER
lP 10
SPEID
RECAL
PULSE
TRACK
ZERO
DRIVE
READY
I ~ ~AIJ---------------------.;_......J
Functional D escription-
Upon initial power application, the up-to-speed counter, up-to-speed latch,
and recalibration latch are all reset. Before the drive can perform any
read, write, or seek operations, it must first become Ready. At
power-on, Ready is a combination of the drive being up-to-speed and an
active Track ~.
As the drive begins to spin, an index pulse from the Index sensor is
supplied to the index counter once each revolution. When the index
counter reaches 512, the drive is assumed to be rotating at its full speed
of 3600 revolutions per minute. The output from the up-to-speed counter
clocks the up-to-speed latch. Since the recalibration latch was reset at
power-on, it will force the direction of the stepper motor outward. If
the heads are not positioned over Track ~, each successive index pulse
will increment the up/down counter. For each increment of the counter,
the phase encoder will select a stepper phase that moves the heads one
half of a track closer to Track~. If the heads are behind Track ~, they
will move to Track ~ immediately, since at power-on the up down counter
will be reset to Phase "A".
When the heads reach Track ~, the recalibration latch will be clocked
high. In its high condition, the recalibration latch will release the
Direction line and block any future index pulses from being gated through
as a step pulse. The recalibration latch, in conjunction with the
up-to-speed latch, will provide the Ready signal to the drive interface.
Approximately 15 milliseconds later, the seek complete timer will cause
the Seek Complete signal to go true.
Seag ate Teclmology
PAGE11
5/1/82

Theory of Operations
ST-506 Service Manual
The active state of Seek Complete is a signal to the controller that
normal operations can begin. The up-to-speed and recalibration latches
will stay set until power is interrupted or drops ·more than 20% below
normal. If this occurs, the recalibration sequen.ce will again be initiated.
Seag ate Technology PAGE 12
5/1/82

Theory of Oper ations
ST-506 Service Manual
2.3.3 Drive Selection
Block Diagram-
LINE DRIVER
to interface
Functlonal 0escI1p tlon-
LINE REOHVER
DRIVE SELECIID
fran interface
to interface
I
SIEP Pi.LSES II
UACK _I
fran interface
to interface
DRIVE SELECf 1I
DRIVE SELECT 2
WRITE GA1E
1
READY
I
DRIVE SELECf 3
fran interface
rI
to inter f ace I
IDRIVE
SELECf 4I
WRITE DATA SEEK <XMPlEIE
fran interface to interface
A~IVIlY ~ I
WR~1E FAU.T I
[ tnternal II
to interface I
IIDEX
to interface
Drive Select serves only to gate other signals to or from the drive
interface. Without Drive Select, the drive cannot read, write, or seek.
Seagate Technology
PAGE 13
5/1/82

Theory of Operations
2.3.4 Step Operation
Block Diagram-
DIRECfICN
ST-506 Service Manual
INIERFACE
STEP
STEP
. PULSE
SE<nD
STEP
DRIVE
SELECf
Functional D escription-
In order to step, the following conditions must be true:
1) Write Gate inactive.
2) Write Fault inactive •
.3) Direction In if Track fJ is true.
4) Drive Ready
5) Step pulse on the interface.
- When a step pulse is applied to the drive interface, the step circuitry
will immediately process it. The pulse is changed to 1.0 microsecond in
width by the monostable multivihrator and is then gated through to the
up/down counter. The counter will count up if the Direction line is low
and will count down if the Direction line is high. An increasing count
will cause the PROM to select motor phases that move the heads toward
Track ~. -The outputs from the PROM are active low which turn off the
pre-ddver transistors. The inactive state of any pre-driver transistor
causes a current flow through the Darlington drivers.
To ensure fast head settling, the stepper motor is always locked between
two phases. For this reason, the stepper circuitry must receive two
steps for each single track increment. Subsequent to receiving an
interf ac e step pulse, an internal step pulse is output by the second step
generator. This second pulse is injected 2.8 milliseconds after the first.
This time interval is the optimum value to take advantage of the motor
momentum and obtain the quickest settling time.
Se ag ate Technology
PAGE 14
5/1/82

Theory of Op er ations
ST-506 Service Manual
Approximately 15 milliseconds after the last internal step pulse, the
retriggerable monostable multivibrator will time out and generate the
Seek Complete signal. Note that during the stepping routine, the
multivwrator is constantly triggered which maintains an inactive signal on
the Seek Complete line.
Se ag ate Technology
PAGE 15
5/1/82