IBM 5251 Series Setup guide

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SY31·0461·3
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IBM 5251 Display Station
Models 1 and 11
, Maintenance Information Manual

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SY31-0461-3
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IBM 5251 Display Station
Models 1 and 11
Maintenance I nformation Manual

Preface
This maintenance information manual is to be used for
servicing the IBM 5251 Models 1 and 11 Display
Station.
Customer engineers using this manual are
assumed
to have completed the course on the 5251
Models 1 and 11 Display Station.
The maintenance
information manual (MIM) has two
major sections: maintenance and theory. Maintenance
includes locations, procedures, and
diagnostic aids.
Theory includes data flow, functional units, and features.
Definitions of terms and abbreviations that are not
common, but are used in the MIM, are in the Glossary
of Terms and Abbreviations.
Setup instructions for the 5251 Models 1 and 11
Display Station are in Appendix A.
Note: MIM pages 1-5, 1-8, 1-27, 1-45, 1-48, 1-49, 1-77,
1-78,1-80,1-81,1-83,1-89,1-91,1-92,1-95,1-96,1-99,
1-100,1-103,3-2, and A-1 have DANGER and/or
CAUTION notices. If desired, translate these notices and
write your own words on the blank lines provided on these
pages.
Fourth Edition (July 1979)
Related Publications
Related information can be found in the following IBM
5250 Informaton Display System manuals:
• IBM 5250 Display System Reference Card,
GX21-9249
• IBM 5251 Display Station Models 1 and 11, IBM
5252 Dual Display Station Operator's Guide,
GA21-9248
• IBM 5251 Display Station Models 1 and 11
Maintenance Analysis Procedures,
SY31-0571
• IBM 5256 Printer Operator's Guide, GA21-9260
• IBM 5256 Printer Maintenance Information Manual,
SY31-0462
• IBM 5256 Printer Maintenance Analysis Procedures,
SY31-0572
• IBM 5252 Dual Display Station Maintenance
Information Manual,
SY31-0492
• IBM 5252 Dual Display Station Maintenance Analysis
Procedures,
SY31-0584
• IBM 5250 Information Display System Planning and
Site Preparation Guide, GA21-9337
This edition has important changes. It obsoletes SY31-0461-2 and Technical
Newsletter SN31-6259. The changes are extensive and the manual should be
reviewed in its entlrety.
Use
this publication only for the purpose stated in the Preface.
Publications are not stocked at the address given below. Make your request for
IBM manuals to your IBM representative or to the IBM branch office for your
area.
This publication could contain errors. Write your comments on the form at the
back of this manual. If the form has been removed, send your comments to IBM
Corporation, Publications, Department 245, Rochester, Minnesota 55901. IBM
may use and distribute any of the information you supply in any way it believes
appropriate without incurring any obligation whatever. You may, of course,
continue to use the information you supply.
© Copyright International Business Machines Corporation 1977, 1978, 1979
iii

The 5251 Models 1 and 11 Display Stations have the
following specific DANGERs:
• Line voltage is present at the power supply and the
display assembly.
• High voltage is present
at the cathode-ray tube.
• The cathode-ray tube could implode if it is hit or if it
falls.
• The green
wire in the display assembly is not at
ground voltage.
iv
Safety

CE SAFETY PRACTICES
All Customer Engineers are expected to take every safety
precaution possible and observe
the following safety practices
while maintaining IBM equipment:
1. You should not work alone under hazardous conditions
or around equipment with dangerous voltage. Always
advise your manager if you MUST work alone.
2. Remove all power, ac and dc, when removing or
assembling major components, working in immediate
areas
of power supplies, performing mechanical
inspection of power supplies, or installing changes in
machine circuitry.
3. After turning off wall box power switch, lock it in the
Off position or tag it with a "Do Not Operate" tag,
Form 229-1266. Pull power supply cord whenever
possible.
4. When it is absolutely necessary to work on equipment
having exposed operating mechanical parts or exposed
live electrical circuitry anywhere in the machine, observe
the
following precautions:
a. Another person familiar with power off controls
must be in immediate vicinity.
b. Do
not wear rings, wrist watches, chains, bracelets,
or metal cuff links.
c. Use only insulated pliers and screwdrivers.
d. Keep one hand in pocket.
e. When using test instruments, be certain that controls
are set correctly and that insulated probes of proper
capacity are used.
f. Avoid contacting ground potential (metal
floor strips,
machine frames, etc.). Use suitable rubber mats,
purchased locally if necessary.
5. Wear safety glasses when:
a. Using a hammer to drive pins, riveting, staking, etc.
b. Power or hand drilling, reaming, grinding, etc.
c. Using spring hooks, attaching springs.
d. Soldering,
wire cutting, removing steel bands.
e. Cleaning parts with solvents, sprays, cleaners,
chemicals, etc.
f. Performing any other
work that may be hazardous to
your eyes. REMEMBER-THEY ARE YOUR EYES.
6. Follow special safety instructions when performing
specialized tasks, such as handling cathode ray tubes
and extremely high voltages. These instructions are
outlined in CEMs and the safety portion of the
maintenance manuals.
7. Do not use solvents, chemicals, greases, or oils that
have not been approved by IBM.
8. Avoid using tools or test equipment that have not been
approved by
IBM.
9. Replace worn or broken tools and test equipment.
10. Lift by standing or pushing up with stronger leg
muscles-this takes strain off back muscles. Do not lift
any equipment or parts weighing over 60 pounds.
11 . After maintenance, restore all safety devices, such as
guards, shields, signs, and grounding wires.
12. Each Customer Engineer is responsible
to be certain that
no action on his part renders products unsafe or
exposes customer personnel to hazards.
13. Place removed machine covers in a safe
out-of-the-way
place where no one can trip over them.
14. Ensure
that all machine covers are in place before
returning machine
to customer.
15.
Always place CE tool kit away from walk areas where
no one can trip over it; for example, under desk or table.
16. Avoid touching moving mechanical parts when
lubricating, checking for play, etc.
17.
When using stroboscope, do not touch ANYTHING-it
may be moving.
18. Avoid wearing loose clothing
that may be caught in
machinery. Shirt sleeves
must be left buttoned or rolled
above the elbow.
19. Ties must be tucked in shirt or have a tie clasp
(preferably nonconductive) approximately 3 inches
from
end. Tie chains are not recommended.
20. Before starting equipment, make certain fellow CEs and
customer personnel are
not in a hazardous position.
21. Maintain good housekeeping
in area of machine while
performing and after completing maintenance.
Knowing safety rules is not enough.
An unsafe act will inevitably lead to an accident.
Use good judgment-eliminate unsafe acts.
ARTIFICIAL RESPIRATION
General Considerations
1. Start Immediately-Seconds Count
Do not move victim unless absolutely necessary to
remove from danger. Do not wait or look for help or
stop to loosen clothing, warm the victim, or apply
stimulants.
2. Check Mouth for Obstructions
Remove foreign objects. Pull tongue forward.
3. Loosen Clothing-Keep Victim Warm
Take care of these items after victim is breathing by
himself or when help is available.
4. Remain in Position
After victim revives, be ready to resume respiration if
necessary.
5. Call a Doctor
Have someone summon medical aid.
6. Don't Give Up
Continue without interruption until victim is breathing
without help or is certainly dead.
Rescue Breathing for Adults
1. Place victim on his back immediately.
2. Clear throat of water, food, or foreign matter.
3. Tilt head back to open air passage.
4. Lift jaw up to keep tongue out of air passage.
5. Pinch nostrils to prevent air leakage when 'You blow.
6.
7.
8.
Blow until you see chest rise.
Remove your lips and
allow lungs to empty.
Listen
for snoring and gurglings-signs of throat
obstruction.
9. Repeat
mouth to mouth breathing 10-20 times a minute.
Continue rescue breathing until
victim breathes for
himself. .
Thumb and
finger positions Final
mouth-to-
mouth position
v

SAFETY .................. .
GLOSSARY OF TERMS AND ABBREVIATIONS
LEGEND .................. .
USING THE IBM 5251 DISPLAY STATION MODELS 1
AND 11 MAINTENANCE INFORMATION MANUAL
Maintenance Procedures Section
Location Drawings . . .
Maintenance Procedures
Mini-MAPs ..... .
Diagnostic
Aids
Preventive Maintenance Section .
Tools and Test Equipment Section
Theory Section .
Features Section
Appendixes
Index
MAINTENANCE PROCEDURES
LOCATIONS ...
100 Front View .
101 Covers Open
102
Cable Chart .
103 Main Planar Board and Card Locations
104 Logic Part Numbers . . . .
105 Main Planar Board Jumpers
COVERS ........ .
108 Display Station Covers . . .
109 Keyboard Covers . . . . .
CONTROL PANEL AND KEYLOCK
110 Control Panel . . . . . . .
111, 112, 113 Control Panel Cable Mini-MAP
Conditions After Power On
Service
Aids . . . . . .
114 Keylock Mini-MAP ...
MAGNETIC STRIPE READER .
115 Magnetic Stripe Reader Voltage and Control
Mini-MAP ........ .
Conditions
After Power On
Service
Aids . . . . . . .
Tools ......... .
116
Magnetic Stripe Reader Register 5 Mini-MAP
Conditions after Power On
Service
Aids . . . . . . . . . . . . . . .
Tools ................. .
117
Magnetic Stripe Reader Registers 5 and 13
Mini-MAP ........ .
Conditions After Power On
Service
Aids . . . . . . .
Tools ..... c' ••••
118 Magnetic Stripe Reader Card Jumpering
119 Magnetic Stripe Reader Installation and Removal
Installation
............. .
Removal .............. .
120 Light Pen Voltage and Control Mini-MAP
Conditions After Power On . . . . . . .
iv
xi
xv
xvii
xvii
xvii
xvii
xvii
xvi
xvii
xvii
xvii
xvii
xviii
xviii
1-1
1-1
1-1
1-2
1-3
1-4
1-5
1-7
1-8
1-8
1-8
1-9
1-9
1-10
1-10
1-10
1-12
1-15
1-15
1-15
1-15
1-15
1-19
1-19
1-19
1-19
1-23
1-23
1-23
1-23
1-26
1-27
1-27
1-27
1-29
1-29
Service Aids . . . . . . . . . . . . . . .
Tools ................. .
121 Light
Pen Register and Control Mini-MAP
Conditions After Power-On
Service Aids . . . . . . . . . . . . . . .
Tools ................. .
122 Light
Pen Register and Control Mini-MAP
Conditions After Power On
Service
Aids . . . . . . . . . .
Tools ............ .
123 Light Pen Tip
Switch Mini-MAP
Service Aids . . . . . . . .
Tools ............ .
124 Light Pen Card Jumpering
125 Light Pen Installation and Removal
Installation
Removal
KEYBOARD
130 Keyboard Locations
131 Keyboard RemovaI and Disassembly
Removal
Disassembly
Assembly .
132 Cleaning
133 Key Module.
Removal
Installation
134 Spacebar
Removal
Installation
135 Flyplate Replacement
136 Keyboard ID Mini-MAP
Conditions After Power On
Service
Aids . . . . . . .
Tools ......... .
137 Keyboard Scan Code Mini-MAP
Conditions After Power On
Service Aids . . . . . . . . . .
Tools ............ .
138 Keyboard Voltage and
Strobe Mini-MAP
Conditions After Power On
Service
Aids . . . . . . . . .
Tools ........... .
139 Keyboard Clicker
Mini-MAP.
Conditions After Power On
Service
Aids . . . . . . . . .
Tools ........... .
140 Keyboard Cable Check Mini-MAP
Conditions After Power On
Service
Aids . . . . . . . .
Tools .......... .
141 Keyboard paR Mini-MAP
Conditions After Power On
Service
Aids . . . . . .
Tools ........ .
142 Keyboard Identification
vi
Contents
1-29
1-29
1-33
1-33
1-33
1-33
1-37
1-37
1-37
1-37
1-41
1-41
1-41
1-45
1-45
1-45
1-47
1-47
1-48
1-48
1-48
1-48
1-48
1-49
1-49
1-49
1-50
1-50
1-50
1-50
1-52
1-52
1-52
1-52
1-54
1-54
1-54
1-54
1-57
1-57
1-57
1-57
1-62
1-62
1-62
1-62
1-64
1-64
1-64
1-64
1-66
1-66
1-66
1-66
1-68

143 Keyboard Arrangement . . .
Keyboard
Template (GX21-9266)
Standard Keyboard Layout
Standard Keyboard Layout (Katakana)
Data-Entry Keyboard Layout (66 Keys)
Data-Entry Keyboard Layout (67 Keys)
Katakana Data-Entry Keyboard Layout (69)
144 Scan Code Table . . . . .
150 Display Assembly Locations .... .
Top View .............. .
151 Display
Assembly Removal and Replacement
Removal
..... .
Replacement. . . . .
DISPLAY ADJUSTMENTS
152 Video Adjustments
Brightness Limiter Potentiometer Adjustment
Contrast Control and Brightness
Control
Adjustments . . . . . . . .
Video Gain/Video Drive Potentiometer
Adjustment . . . . . . . . . . . .
153 Vertical and Horizontal
Adjustments
Vertical Adjustments . .
Horizontal
Adjustments . . .
154 Yoke Adjustment (150) ..
155 Centering Adjustment (150)
Factory Adjustments. . . . . .
Focus
Potentiometer Adjustment
B+ Potentiometer Adjustment
156 Raster . . . . . . .
Raster Check
.... . . . .
157 Display
Assembly Cable Mini-MAP
Conditions After Power On
Service Aids . . . . . . .
Tools ......... .
158 Display Screen Examples
SYSTEM CABLE . . . . . .
170 Customer System Cable Signal Quality Check
171 Internal System Cable and
Terminator Switch
172 Typical Display Station Configuration
173 Station Protector and Lightning Protector .
Station Protector . . . . . . .
Typical Installation . . . . . .
Typical Station Protector Board
Lightning Protector . . . . . .
174 Cable Assembly Procedures.
Assembly of Twinaxial Cable
Assembly of Coaxial Cable
Twinaxial-Coaxial Adapter
Adapter Service Check
Cable Labeling . . . . . .
Tests
of Cabling After Installation
POWER SUPPLY . . . . . . . . .
180 Power Supply Locations . . .
181 Power
Supply Removal and Replacement
Removal
...... .
Replacement. . . . . . . . . . .
182 Voltage Level Checks
.....
183 Power Supply Ripple Level Check
184 Power Supply Charts
US Power
Supply . . . . . . . .
World Trade Power Supply
185 Line Cordi Line Filter Removal and Replacement
187 Power
Supply Fan Removal and Relplacement
Removal
Replacement. . . . . . . . . . . . . . . . .
1-69
1-69
1-69
1-69
1-70
1-70
1-71
1-73
1-75
1-76
1-77
1-77
1-77
1-78
1-78
1-78
1-78
1-78
1-78
1-79
1-79
1-79
1-80
1-80
1-80
1-80
1-81
1-81
1-83
1-83
1-83
1-83
1-86
1-89
1-89
1-89
1-90
1-91
1-91
1-91
1-91
1-92
1-94
1-94
1-96
1-97
1-97
1-97
1-97
1-98
1-98
1-99
1-99
1-99
1-100
1-101
1-101
1-101
1-102
1-103
1-103
1-103
1-103
188 Light
Pen Power Supply Card
Removal and Replacement
1-103
Removal
1-103
Replacement .
1-103
DIAGNOSTIC AIDS
1-104
200 Control Panel LEDs
1-104
Line Sync
1-104
Line Check
1-104
Internal Check
1-104
Storage Check
1-104
Ready
1-104
201 Status Switch
1-105
202 Field Attribute Characters .
1-107
203 Display Station Operation Overview
1-108
204 Power-On Diagnostic
1-109
Power-On Diagnostic Flowchart (Part 1 of 3)
1-109
Power-On Diagnostic Flowchart (Part 2 of 3) 1-110
Power-On Diagnostic Flowchart (Part 3 of 3) 1-111
205 Free Key Operation 1-112
Free Key Mode Flowchart
1-112
206 Online Tests
1-113
Online Tests Overview 1-114
Online Tests Displays .
1-115
207 Sign-On Procedure
1-128
208 Error History Table 1-129
209 Error Codes .
1-130
Display Station Error Codes
1-130
Operator Error Codes
1-132
210 Diagnostic Display Locations 1-135
Cursor Display Positions 1-135
Power-On Diagnostic Display 1-135
212 Troubleshooting Aids 1-136
PREVENTIVE MAINTENANCE. 2-1
TOOLS AND TEST EQUIPMENT 3-1
CE General Logic Probe(Part 453212) 3-2
THEORY. 4-1
INTRODUCTION 4-1
System Configuration 4-1
DATA FLOW 4-3
FUNCTIONAL UNITS
4-4
I/O Adapter Control 4-4
Keyboard 4-5
Clicker
4-5
Keyboard Identification 4-5
Display Adapter .
4-6
Buffering and. Displaying 4-7
Control Panel . 4-8
Display Screen 4-9
Field Attributes 4-9
Display Screen Indicators 4-9
Cable Adapter 4-9
The 16-Bit Frame 4-9
Transmission Sequences 4-11
Commands
4-12
Response Frame
4-14
Interface
4-16
Data Transfer 4-17
Microprocessing Unit (MPU) 4-18
Read/Write Storage 4-18
Internal Processing Queue
4-18
Control Registers .
4-19
Contents vi i

viii
FEATURES. 5-1
Keylock Feature. 5-1
Cable Thru Feature 5-2
Magnetic Stripe Reader Feature . 5-3
Read Data
Word
5-4
Selector Light or Pen Feature 5-5
Theory
of Operation 5-5
APPENDIX A. DISPLAY STATION SETUP
INSTRUCTIONS . A-1
SETUP INSTRUCTIONS-SECTION 1 A-1
SETUP INSTRUCTIONS-SECTION 2 A-2
APPENDIX B. SELF-CHECK FEATURE. B-1
Self-Check Feature 8-1
Computing the Self-Check Digit 8-1
INDEX.
X-1

ix

x
This page is intentionally left blank.

p.f: Microfarad.
activity: Action or process.
addr: Address.
alpha: Alphabetic.
ALU: Arithmetic logic unit.
amplifier: A device that increases a voltage or a signal
to a usable level.
anode: A positive terminal of a diode.
arithmetic: The adding, subtracting, multiplying, or
dividing
of two or more numbers.
attribute: A characteristic that controls how data is
displayed on the display screen. For example, the
attributes
of a display field include blinking, high
intensity, and reverse image.
blink attribute: An attribute of a display field that
causes the characters to flash.
brightness limiter potentiometer: A potentiometer
that prevents too much brightness. See reference 150.
buffer: A temporary storage area.
Cable Thru feature: A special feature that permits
multiple display stations or printers to be attached
serially
to a system cable.
callout: A character used to identify a particular portion
of an illustration.
capacitive: Having capacitance.
cathode: A negative terminal of a diode.
char: Character.
character matrix: A part of the display screen
character
window. The character matrix is 16 dots high
by 8
dots wide.
••
., ..
. . .
Glossary of Tenns and Abbreviations
character window: A part of the display screen that is
24
dots high by 10 dots wide and includes the character
matrix.
clicker: A solenoid in the keyboard that makes a sound
after each keyboard character has been received by the
display station.
Cmd key: The command key on the keyboard that is
used
to select command functions.
column separator: A vertical bar in a field of data that
separates all characters in that field.
command function keys: The 14 keys on the top row
of the display station keyboard that are used with the
Cmd (command) key to request functions.
cont: Controller.
Contrast control: The device that changes the contrast.
See reference 100.
controller: A device that controls the operation of one
or more input or output devices.
data stream: A continuing flow of data.
diag: Diagnostic.
driver: A source that sends (drives) a signal from one
location to another. See reference 212.
dual: Having two similar parts.
Dup key: The key on the keyboard that is used to
duplicate a field from a preceding field.
EOM: End of message.
end-of-message delimiteJ: A 111 in the station ID field
that indicates the last frame of a message block.
EOQ:
End of queue.
ERAP: Error recording analysis procedures.
xi

field attribute: The control characters that describe a
displayed field. For example, a display field can be
intensified, reversed, underscored,
or made to blink.
flyplate: The bottom of a key module. See reference
135.
FRU: Field-replaceable unit.
hex: Hexadecimal.
HH:MM:SS: Hours, minutes, and seconds.
10: Identification.
implode: To break inward suddenly.
Ins key: The key on the keyboard that is used to select
the insert mode.
IPL: Initial program load.
KBD: Keyboard.
key stem: The connecting part between the key top and
the key module. See reference 135.
Keylock feature: A feature with a lock and key that
restricts the use of the display station.
keystroke: The action of pressing a key on the
keyboard.
LED:
Light-emitting diode.
linearity: The size of displayed characters of equal
width.
line turnaround: The time between the reception of the
last bit
of a frame by a work station and the start of
transmission by that same work station.
LP: Light pen.
LRC: Longitudinal redundancy check.
main planar: The basic printed circuit electronic board
used in the display station.
make/break key: A key that generates a scan code
when the key is pressed and when
it is released.
mandatory: Something that must be done or must be
present.
menu: A list of options that can be selected.
microfarad: One millionth part of a farad.
microinstruction: A basic or elementary machine
instruction.
microprocessing: Operations performed by the MPU.
xii
microprocessing unit (MPU): A processing unit that is
microprogram controlled and performs internal machine
operations. The MPU receives data, controls the display
of data, and controls the flow of information to and
from the controller.
microprogram: A program that uses microinstructions
to carry out system operations.
mini-MAP: A maintenance analysis procedure that is
located in
the maintenance information manual. A
mini-MAP continues the failure analysis after one of the
other MAPs has located the area that is failing.
MPU: Microprocessing unit.
MSR: Magnetic Stripe Reader feature.
mm: Millimeter.
ms: Millisecond.
msg: Message.
MSIPL: Main storage initial program load.
multiframe response: More than one frame of data is
being sent.
N/C: Pertains to a switch setting; normally closed.
N/O: Pertains to a switch setting; normally open.
null: A hex character composed of all zeros; this
character occupies a position in
the buffer and is
displayed as a blank.
online test: A series of tests that can be requested
from the system after power on and before sign-on.
See reference 206.

option: One of the items listed on a display screen
menu.
overview: A short description.
P-P: Peak-to-peak.
pc: Printed circuit.
planar: See main planar.-
PM: Preventive maintenance.
poll: A method the controller uses to determine if a
display station is ready to send or receive data.
POR: Power on reset.
port: The place where a cable is connected to a
machine.
protector: A device that aids in preventing injuries to
persons or damage to machines.
R/D: Receiver/driver.
raster: The image on the CRT that is made by the
action
of the CRT electron beam as it scans across the
area
of the CRT where data is displayed. Normally, the
intensity
of the raster is not high enough to be visible.
However, the raster can be displayed if you install a
raster check jumper.
read-only storage (ROS): A storage area in the MPU
from which data can be read but not changed.
read/write storage: A storage area in the MPU that
stores information for later use; the information can be
changed
by the MPU.
receivers: Those parts that accept data or voltages.
refresh: To continuously redisplay data on the display
screen to prevent the data from fading out; the display
adapter refreshes the data.
regen buffer: An area in read/ write storage where data
is stored before
it is displayed.
register: A storage device or circuit that stores those
limited parts of data needed by the system to execute
input/ output, storage, processing, and control
operations.
related: Having a common use.
required: See mandatory.
resolution: The visual quality of display screen data.
retaining ears: The projections located on the bottom
of a key module; these projections hold the module to
the frame. See reference 133.
retrace lines: The lines that appear on the display
screen when the display adapter returns the sweep to
the upper left corner of the display screen. Retrace lines
are normally blanked out. See reference 156.
retry: To repeatedly send frames of information until
the frames are received without an error by the display
station; the controller sends the frames.
ripple: Small waves present on DC voltages.
ripple level: A measurement of the AC voltage carried
on the
DC voltage.
rolling: Pertains to movement on a display screen; the
movement can be either horizontal, vertical, or a
combination
of both.
ROS: Read-only storage.
rt adj: Right adjust.
serdes: Serializer/ deserializer.
serializer/deserializer (serdes): A register that is used
to send and receive data between the display station
and
the controller.
setup: To prepare a device for operation.
sign-on: A logon procedure performed at a display
station; the procedure can include entering the sign-on
command, a password, or other user specified security
information.
slot: A narrow opening or groove.
SOM: Start of message.
stabilizer: A rod on the Spacebar. See reference 134.
xiii

stat addr: Station address.
stem: See key stem.
stiffener: A part used to supply rigidity to a logic card
or planar.
storm: Electrical discharges in the air.
strain relief cable: A cable that supports the planar.
SVCS: Services.
SYS: System.
Sys Req key: A key that is used to send a request
directly to the system.
taper: Increasing in size toward one end.
TB: Terminal block.
Terminator switch: A switch used to terminate the
customer system cable at the last display station or
printer in a series. This switch is a part of the Cable
Thru feature on a display station.
theory: A section of this manual that includes data
flow, functional units, and features.
transfer: To move from one person, place, or thing to
another.
twinaxial cable: A shielded twisted-pair cable that
connects a display station or printer to a controller.
typamatic key: A repeat-action key on the keyboard.
undefined: The meaning is not known or described.
underscore: A line under all positions of a field.
Underscore is controlled by an attribute.
US: United States.
Vac: Volts alternating current.
Vdc: Volts direct current.
verification: Testing an operation or machine.
video: Pertains to the display screen image.
YY /MM/DD: Year, month, and day.
xiv

Legend
The following symbols are u
sed in
flowcharts and
figures
throughout this manual.
i'
Zener Diode
CJ
Display Screen
--of- Diode
( ) Start and End
~~
Capacitor
of Flowchart
V Off-Page
J,-J-
Ground
Connector
0 On-Page
]111 [
Connector
Transformer
0 Decision
Block
p~
Relay
C
Comment
.-r
Contact (relay
Block
not energized)
L
D
Information
~
Contact (relay
Block
energized)
L
-{>
Logic (indicates
Resistor
signal direction)
Driver
"-',
Jumper
" 0--
--0
i2=r
Logic
Driver
IRecei'ver
-B- Relay Driver
H Detector
Legend 5251
MIM
xv

xvi
This page is intentionally left blank.

Using the IBM 5251 Display Station Models 1 and 11 Maintenance Information Manual
The information in this MIM is to be used as reference
material when you are diagnosing machine failures. This
MIM contains a Maintenance Procedures section, a
Preventive Maintenance section, a Tools and Test
Equipment section, a Theory section, and a Features
section. Appendixes give general information (such as
setup procedures) that is not directly related to the
maintenance
of the 5251 Models 1 and 11 Display
Station.
The
format for page numbering is X-VYY.Z. X is the
section number, YYY is the page number, and Z
(although not normally used) is the number used for
expansion when it is not practical to give new numbers
to all pages.
Three-digit reference numbers are assigned to location
drawings and maintenance procedures
that are referred
to in the MAPs. For example, 130 indicates the
keyboard locations
of the display station.
MAINTENANCE PROCEDURES SECTION
The Maintenance Procedures section contains location
drawings, maintenance procedures,
mini-MAPs, and
diagnostic aids
for repairing, installing, or diagnosing the
failing FRUs
(field- replaceable units).
Location Drawings
Location drawings show the position of the parts in the
display station.
Maintenance Procedures
Maintenance procedures contain removal, replacement,
and adjustment procedures. All procedures and
drawings have assigned
three-digit reference numbers.
Mini-MAPs
You are sent to mini-MAPs to continue the failure
analysis
to locate a failing field- replaceable unit.
In general, mini- MAPs provide you with three levels of
information:
1.
2.
A figure showing the circuit line names and pin
numbers.
A description
of the circuit and how it can be
tested.
3. A detailed guide that uses the yes and no path of
questions that you can follow to isolate the failure.
You can select the level
of information you need to
locate a failing field-replaceable unit.
Diagnostic Aids
Diagnostic Aids describe diagnostic programs, how to
use them, and what is available when they are in
control. To aid in diagnosing machine failures in
more detail, a list
of error conditions is included.
PREVENTIVE MAINTENANCE SECTION
The Preventive Maintenance section describes any
preventive maintenance required by the display station.
TOOLS AND TEST EQUIPMENT SECTION
The Tools and Test Equipment section describes the tools
that are needed to service the display station.
THEORY SECTION
The Theory section describes the functional units and
features. These descriptions are preceded by a
view of
the system that gives you a general idea of the
complete operation and how each function or feature
relates
to the operation.
FEATURES
SECTION
The Features section describes the features that are
available
with the 5251 Models 1 and 11 Display
Station.
Using the MIM 5251 MIM xvii

APPENDIXES
Appendix A contains the setup procedures required to
make a new display station operational. Appendix B
explains the operation of the Self-Check feature.
Self-Check is a host system feature.
INDEX
The index is a detailed list of all the material contained
in the
MIM.
xviii

100
locations
100 FRONT VIEW
Display Screen
--
--
--
--
--
--
--
--
--
--
--
:::===
--
SYstem Cable- __ ~~ _____ ;-"""
Connector
(socket
1)
Address SWitches
•
•••
. . .'
....
Maintenance Procedures
Bezel
Display Screen Indicators
Connector (socket 2) Access Panel Cover
Keyboard Cable Connector
Maintenance Procedures 5251 MIM 1-1

1-2
101 COVERS OPEN
Main Planar Board
Display Assembly
------
The covers are sh
. own
pivoted open.
Power Supply
Line Filter