IBM 3279 2A Setup guide

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- - - ~ - Maintenance Library
=-=-=-=- -s 3 G
=~ ffff: ~ Color Display Station
Models 2A , 28 , 3A , and 38
Maintenance Infonnation
SY33-0069-3
(Part 1)

=~ff-;: ~
Maintenance Library
Color Display Station
Models 2A, 28, 3A, and 38
Maintenance Information
SY33-0069-3
(Part 1)

3279 MIM
Preface
Part 2 comprises the Maintenance Analysis
Procedures.
ii
This publication contains the information needed to
service and maintain the IBM 3279 Color Display
Station Models 2A, 2B, 3A, and 3B.
Part 1 comprises the Maintenance Information and
Parts Catalog.
If this machine is fitted with any RPQ features, any
extra RPQ documentation can he found in a tray
under the keyboard.
Fourth Edition, November 1981
This is a major revision of, and obsoletes, SY33-0069-2. The drawings
and specifications contained herein shall not he reproduced in whole or in
part without written permission.
IBM has prepared this maintenance manual for the use of IBM customer
engineers in the installation. maintenance, or repair
of the specific
machines indicated. IBM makes no representations
that it is suitable for
any
other purpose.
Information contained in this manual
is subject to change from time to
time. Any sllch change will be reported in subsequent revisions or
Technical Newsletters.
It is possible that this material may contain references to, or information
abollt, IBM products (machines or programs), programming,
or services
that are not announced in your country. Such references or information
must
not be construed to mean that IBM intends to announce such IBM
products, programming,
or services in your country.
Publications are not stocked
at the addresses given below; requests for
IBM publications should be made
to your IBM representative or to the
IBM
branch office serving your locality.
A form for reader's comments
is provided at the back of this publication;
if the form has been removed, comments may be addressed
to either:
• International Business Machines Corporation, Department 812H,
1133 Westchester Avenue, White Plains, New York 10604.
or
IBM United Kingdom Laboratories Limited, Product Publications, Mail
Point 95, Hursley Park, Winchester, Hampshire
S021 2JN, England.
IBM may use or distribute whatever information you supply
in any way it
believes appropriate without incurring any obligation to you.
e Copyright International Business Machines Corporation 1979, 1980,
1981

Contents
Chapter 1. General Description and Locations
1.1 Introduction
1-1
1.1. 1 Controls 1-1
1. 1. 2 Indicators 1-2
1.2 Display Unit 1-2
1.2.1 Electrical Grounding 1-2
1.2.2 Equipment Lightning Protection 1-2
1.2.3 Video 01)tput Facility 1-2
1.3 Keyboards 1-9
1.3.1 Scan Codes 1-9
1.3.2 Break Codes 1-9
1.3.3 Keyboard Cable 1-9
1.3.4 System Upshift 1-9
1.3.5 Keyboard Type Identification 1-9
1.3.6 Keyboard Lock 1-9
1.3.7 Numeric Lock (Feature) 1-9
1.4 Tools and Test Equipment 1-9
1.4.1 General Logic Probe 1-10
Chapter 2. Maintenance Aids 2-1
2.1 Maintenance Plan 2-1
2.2 General Failure Index 2-1
2.3 MAPs 2-1
2.4 Intensity Override 2-1
2.S Test Modes (Offline) 2-1
2.S.\ Test Mode 1: Pattern 2-\
2.S.2 Test Mode 2: Keyboard 2-3
2.S.3 Test Mode 3: Commands 2-4
2.6 Online Tests (Control Unit to Display
Station) 2-S
2.6.1 Running Online Tests 2-6
2.6.2 Test 0
2-6
2.6.3 Test 1: Error Log 2-9
2.6.4 Test 3: Status Summary
2-\0
2.6.S Test 4: Error Log Reset 2-\0
2.6.6 Test 7: Operator Convergence Utility
2.6.7 Test 8: 7-Color and Programmed
Symbols (PS) 2-10
2.6.8 Error Codes 2-\\
2.7 Jumper Positions 2-13
Chapter 3. Functional Components
3-1
3.1 Power Supply 3-2
3.2 Analog Card 3-2
3.3 Amplifier Card
and Inputs 3-4
3.3.1 Convergence Circuits 3-4
3.3.2 Color Controls
3-6
3.4 Video Card 3-6
3279 MIM
1-1
2-10
3.S Cathode Ray Tube and Coil Assembly 3-6
3.6 Convergence Logic Card (Location B2) 3-8
3.7 Line Control Card (Location C2) 3-9
3.8 Base Logic Card (Location
02) 3-9
3.9 APL/Extended Character Set (ECS) Card
(Location E2) 3-11
3.10 Programmed Symbols (PS) Card (Feature)
(Location
F2) 3-12
3.11 Selector Light Pen (LP) Card (Feature)
(Location
G4) 3-13
3.12 Magnetic Reader Control (MRC) Card
(Feature) (Location
G2) 3-13
Chapter 4. Removal and Replacement
Procedures 4-1
4.1 General 4-1
4.2 Logic
Gate 4-\
4.3 Rear Cover 4-1
4.4 Bezel 4-1
4.4.1
ON/OFF Switch 4-2
4.4.2 Brightness and Audible Alarm
Volume Controls 4-2
4.4.3
Normal/Test, Base Color. and
Oualcase/Monocase Switches 4-2
4A.4 Indicator LEOs 4-3
4A.S Security Keylock 4-3
4.S Power Units 4-3
4.S.1 Fuse 4-3
4.S.2 Power Supply 4-3
4.S.3 Prime Power Box 4-3
4.S.4 Analog Card 4-4
4.6 Logic Cards
4-4
4.6. I Removal 4-4
4.6.2 Replacement 4-4
4.7 Connectors 4-5
4.7.\ Multi-Pin Connections 4-S
4.7.2 Internal Coaxial Connection 4-S
4.8 Video Components 4-7
4.8.\ Amplifier Card 4-7
4.8.2 Video Card 4-7
4.8.3
CRT and Coil Assembly 4-7
4.8.4
EHT Bleed Assembly 4-9
4.8.S Degauss Coil 4- 10
4.9 Logic. Board Planar Strips 4-10
4.9.1 Removal 4-10
4.9.2 Replacement 4-\0
4.10 Audible Alarm 4-1 \
iii

3279 MIM
iY'
4.1 I Keyboard Units 4-11 Chapter
6. Support Information 6-1
4.11.1 Keyboard From Display Station 4-11
6. 1 Block Diagram 6-1
4.11.2 Keyboard Top Cover 4-11 6.2 3279 Control Signals 6-2
4.11.3 Keyboard Assembly From Base 4-11 6.2.1 Waveforms 6-2
4.11.4 Clicker Assembly 4-11 6.2.2 Activation Sequence 6-5
4.11.5 Keybutton 4-11 6.3 Top Card Connector and Planar
4.11.6 Key Modules 4-12 Strip Wiring 6-5
4.11.7 Spacebar 4-13 6.4 Grounding and Cables 6-18
4.11.8 Logic Card Assembly 4-13 6.5
CRT Drive Circuits 6-25
6.6 Bezel Wiring 6-26
Chapter 5. Display Adjustments 5-1
5.1 Initial Checks 5-2
5.2 Coarse Adjustments 5-2
5.2.1 Coarse Color Balance 5-3
6.7 Keyboard Jumpers and Cables 6-28
6.8 Attachment Cabling 6-30
6.9 ECS and PS Card Layouts 6-32
6.10 Power Supplies 6-33
5.2.2 Coarse Raster Adjustment 5-3
5.2.3 Coarse Focus 5-3
6.11 Display Attributes and Modified
Data Tags 6-34
5.2.4 Coarse Static Convergence 5-3 6.12 Extended Character Set Buffer 6-35
5.2.5 Coarse Color Purity 5-4
5.3 Fine Adjustments 5-4 Appendix
A. Indicators In Operator
5.3.1 Static Convergence 5-4 Information Area
A-I
5.3.2 Purity 5-4
5.3.3 Dynamic Convergence (Online Test
7) 5-5 Abbreviations and Glossary
G-I
5.3.4 Focus Adjustments 5-5 Abbreviations G-I
5.3.5 Raster Controls 5-6 Glossary G-3
5.3.6 Red Brightness 5-7
5.3.7 Color Balance 5-7 Parts Catalog
5.3.8 Repetition 5-8
5.3.9 Convergence Amplifier Gain Controls 5-8 Index
X-I

Figure 1-l.
Figure 1-2.
Figure 1-3.
Figure 1-4.
Figure 1-5.
Figure 1-6.
Figure
2-l.
Figure 2-2.
Figure 2-3.
Figure 2-4.
Figure 2-5.
Figure 2-6.
Figure 2-7.
Figure 2-8.
Figure 2-9.
Figure 3-1.
Figure 3-2.
Figure 3-3.
Figure 3-4.
Figure 3-5.
Figure 3-6.
Figure 3-7.
Figure 3-8.
Figure 4-1.
Figure 4-2.
Figure 4-3.
3279 MIM
Controls and Indicators
I-I
Display Unit -Front View with
Bezel Removed 1-4
Display Unit -Rear View
1-5
Display Unit -Rear View, Open 1-6
Display Unit -Interior View 1-7
Logic Card and Top Card Connector
Locations (card side) 1-8
Illtensity Override (Test Mode) 2-2
Test Mode 1 Pattern 2-3
Keyboard Character Interpretation
for Test Mode 2 2-3
Online Test 0 Pattern 2-7
Test 1 Pattern 2-9
Test 3 Pattern 2-10
Test 8 Pattern 2-11
Error Codes From
IBM 3274
Control Unit 2-12
Error Codes From
IBM 3276
Control Unit 2-13
3279 Block Diagram 3-1
Power Supplies to Logic Gate
and Analog Card 3-3
Synchronization, Convergence, Purity.
and Deflection Coil Connections 3-5
Shadow Mask 3-7
Convergence Logic Card (B2) 3-8
Base Logic Card
(02) and Uoe
Control Card (C2) 3-10
APL/ECS 'Card (E2) 3-11
Programmed Symbols Card
(F2) 3-12
General View -Bezel Removed 4-1
ON/OFF Switch 4-2
Brightness and Audible Alarm Volume
Control Assembly 4-2
Figure 4-4.
Figure 4-5.
Figure 4-6.
Figure 4-7.
Figure 4-8.
Figure 4-9.
Figure 4-10.
Figure 5-1.
Figure 5-2.
Figure 5-3.
Figure 6-1.
Figure 6-2.
Figure 6-3.
Figure 6-4.
Figure 6-5.
Figure 6-6.
Figure 6-7.
Figure 6-8.
Figure 6-9.
Figure 6-10.
Figure 6-I 1.
Figure 6- 12.
Figure 6-13.
Figure 6-14.
Figure 6-15.
Figure 6-16.
Figure 6-17.
Figure 6-18.
Figure 6-19.
Figure
A-I.
Switches 4-2
Indicator LED Assembly 4-3
Logic Card Removal and
Replacement 4-5
Analog Card 4-6
Convergence/Purity Coil
Assembly 4-9
Planar Strip Holders 4-10
Audible Alarm Assembly 4-11
Adjustment Procedure
5-1
Voltage Table 5-2
CRT Alignment Mask 5-6
3279 Block Diagram 6-1
Waveforms (3 Parts) 6-2
Top Card Connectors (4 Parts) 6-5
Planar Strips -
BD (4 Parts) 6-11
Grounding Diagram 6-18
Cabling Diagram 6-19
CRT Drive Circuits 6-25
Bezel Wiring 6-26
Video Card Test Points 6-27
Amplifier Card Test Points 6-27
Keyboard Logic and Connector 6-28
Logic Gate to Keyboard Cable 6-29
Attachment Cabling (2 Parts) 6-30
ECS and
PS Card Layouts 6-32
Mainline Supply 6-33
Supplies to Amplifier Card 6-33
Base Field Attribute Byte 6-34
Attribute Characters 6-35
ECS Byte 6-36
Layout of Operator Information
Area
A-I
v

3279 MIM
Safety Guidelines
If you are aware of the guidelines for working
with electrical and mechanical equipment and
practice these guidelines, you can
work safely
with this equipment.
You need. not fear electricity, but you must
respect it.
You should take every safety precaution
possible and observe the following safety
pactices while 'maintaining IBM equipment:
1. You should not work alone under hazardous
conditions or around equipment with
dangerous voltage. Always advise your
manager if this is a potential problem.
2. Remove all
power before removing or
assembling major components, working in
the immediate area
of power supplies,
performing mechanical inspection of power
supplies, or installing changes in machine
Circuitry.
3. Power supplies, pumps, blowers, motor
generators, and other units with voltages
Which exceed 30 V ac or 42.4 V dc must not
be serviced with power on when the unit is
removed from its normal installed position
within the machine, unless maintenance
documentation clearly states otherwise.
(This
is done to ensure that proper
grounding is maintained.)
4. Unplug the
power supply cord whenever
possible before working on the machine.
The
wall box switch when turned off should
be locked in the
off position or tagged with
a DO NOT OPERATE tag (form Z229-0237).
Be aware that a non-IBM attachment to an
IBM machine may be powered from another
source and be controlled
by a different
disconnect or circuit breaker.
5.
When it is absolutely necessary to work on
equipment having exposed live electrical
circuitry, observe the following precautions:
a. Another person familiar with power off
controls must be in immediate vicinity.
(Someone
must be there to turn off
power if it should become necessary.)
vi
b. Do
not wear any jewelry, chains, metallic
frame eyeglasses,
or metal cuff links. (In
the event
of contact, there will be more
current flowing because of the greater
contact area afforded by the metaL)
c. Use
only insulated pliers, screwdrivers,
and appropriate probe tips/ extenders.
(Remember, worn or cracked insulation is
unsafe.)
d. Use only one hand
when working on
energized equipment. Keep the
other
hand in your pocket or behind your back.
(Remember there
must be a complete
circuit
for electrical shock. This
procedure helps eliminate a path
that
could complete a circuit through you!)
e. When using test equipment, 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.
6.
Follow special safety instructions when
working with extremely high voltages.
These instructions are outlined in CEMs and
the safety portion of maintenance
documentation. Use extreme care
when
checking high voltage.
7.
Avoid use of tools and test equipment that
have not been apPllf)ved by IBM. (Electrical
hand
tools [wire wrap guns, drills, etc.]
should be inspected periodically.)
8. Replace
worn or broken tools and test
equipment.
9. -After maintenance, restore all
safety devices,
such as guards, shields, signs, and ground
leads. Replace any safety device that is
worn or .defective. (These safety devices
are
there to protect you from a hazard.
Don't defeat their purpose by not replacing
them at the completion of the service call.)

10. Safety glasses must be worn when:
Using a hammer to drive pins, etc.
Power hand drilling.
• Using spring hooks, attaching springs.
Soldering, wire cutting, removing steel
bands.
Parts cleaning, using solvents, chemicals,
and cleaners.
All other conditions which might be
hazardous to your eyes.
11. Never assume that a circuit is deenergized.
(Check
it first.)
12.
Always be alert to potential hazards in
your working environment (i.e., damp floors,
nongrounded extension cords, power surges,
missing safety
grounds, etc.).
13. Do
not touch live electrical circuits with the
surface
of the plastic dental mirrors. The
surface
of the dental mirror is conductive
and can result in machine damage and
personal injury.
14. Four
steps that should be taken in the
event of an electrical accident:
a. USE CAUTION -DON'T BE A VICTIM
YOURSELF.
b. TURN POWER OFF.
c. HAVE SOMEONE ELSE GET MEDICAL
HELP.
d. ADMINISTER RESCUE BREATHING
IF
VICTIM IS NOT BREATHING.
15. Do not use solvents, cleaners, or oils that
have not been approved by IBM.
16. Lift by standing or pushing up with
stronger leg muscles. This takes strain off
back muscles. Do not lift any equipment or
parts which you feel uncomfortable with.
17. Each customer engineer is responsible to
be certain that no action on his/her part
renders the product unsafe or exposes
hazards
to customer personnel.
18. Place removed machine covers in a safe
out-of-the-way location while servicing the
machine. These covers
must be in place on
the machine
before the machine is returned
to the customer.
3279 MIM
19. Always place CE tool kit away from walk
areas where no one can trip ovor it (i.e.,
under
desk or table).
20.
Avoid wearing loose clothing that may be
caught in machinery. Shirt sleeves
must be
left buttoned or rolled up above the elbow.
Long hair and scarves must be secured.
21. Ties
must be tucked in shirt or have a tie
clasp (preferably non-conductive)
approximately three inches from the end
when servicing a machine.
22. Before starting equipment, make sure
that
fellow CEs and customer personnel are not
in a hazardous position.
23. Maintain
good housekeeping in the area of
the machines while performing and after
completing maintenance.
24.
Avoid touching moving mechanical parts
when lubricating, checking for play, etc.
Prevention is the key to electrical safety. You
should
always be conscious of electrical safety
and practice
good habits such as:
Making certain
that the customer's power
receptacle meets IBM equipment
requirements.
Inspect line cords and plugs. Check for
loose, damaged or worn Pl,lrts.
Before removing a component which can
retain a charge from the machine, review the
procedure in the maintenance documentation.
CAREFULLY discharge the necessary
components exactly as directed by the
service procedure.
Do
not use an ordinary lamp as an extension
trouble light.
Never assume anything about a machine or
circuit. No machine is completely safe a/l of the
time. The exact condition
of a machine may be
unknown. Here are some of the reasons why:
The power receptacle could be incorrectly
wired.
Safety devices or features could be missing
or defective.
The maintenance and/
or modification history
may be uncertain or unclear.
vii

3279 MIM
A possible design deficiency could exist.
The machine may have suffered
transportation damage.
The machine might have an unsafe alteration
or attachment.
An EC or sales change may have been
improperly installed.
The machine
may have deteriorated due to
age or environmental extr8mes.
Electrical Accidents
Administering First Aid
In implementing rescue procedures in an
electrical accident one must
Use Caution If the victim is still in contact
with the electrical so~rce, it may be
necessary to use the room EPO (Emergency
Power Off) or disconnect switch to remove
the electrical current. If the EPO or
disconnect switch cannot be located, use a
dry stick or another nonconducting object to
pull or push the victim away from contact
with the electrical equipment.
Act Quickly If the victim is unconscious,
helshe may need rescue breathing and
possibly external cardiac compression if the
heart is not beating.
Call Fire Rescue (Rescue Squad,
Emergency, Ambulance, Hospital etc.) Have
someone summon medical aid.
Determine if the victim needs rescue breathing.
1.
Make certain that the victim's airway is open
and that it is not obstructed. Check the
mouth for objects that may be blocking the
airway such as gum, food, dentures or even
the tongue. Position the victim on his back
and place one hand beneath the victim's
neck and the other hand on his forehead.
Then lift the neck with one hand and tilt the
head
backward with pressure on the
forehead from the other hand as shown in
Figure 1.
viii
A component could be defective, creating a
hazard.
Some component of the machine may have
been
incorrectly assembled.
Relating to safety, these are some of the ways
the condition of the machine can be affected.
Before you begin a service call or procedure,
exercise good jud!!ment and proceed with
caution.
2. Now you must look, listen, and feel to
determine if the victim is breathing freely,
Place your cheek close to the victim's mouth
and nose to listen and feel for the exhaling
of air,
Figure 1
At the same time, look at the chest and
upper abdomen to see if they rise and fall,
If the victim is not breathing properly, you
should:
a. With the head in a backward tilt as
shown in Figure 1, continue to exert
pressure on the victim's forehead with
your hand while rotating this same hand
so that you can pinch the victim's
nostrils together with the thumb and
index finger (Figure 2),
CAUTION
Use extreme care when administering
reSCue breathin!! to a victim that may
have breathed in toxic fumes, DO
NOT INHALE AIR EXHAUSTED BY
THE VICTIM,

Figure 2
b. Open your mouth wide and take a deep
breath. Make a
tight seal with your
mouth around the victim's mouth and
blow into the victim's mouth (Figure 3).
Figure 3
c. Remove your mouth and allow the victim
to exhale while watching for the victim's
chest to fall (Figure 4).
Cathode Ray Tube Safety
The primary hazard of CRTs is flying glass as a
result· of an implosion. The following sections
deal
with different phases of CRT SAFETY, All
phases are equally important and negligence in
any area could result in
possible injury to an
employee
or customer.
Any additional information or variation from this
information will be included under that specific
unit's CEM/Service Aids.
Storage of Cathode Ray Tubes
1. Cathode Ray Tubes must be enclosed when
received, transported, or otherwise moved
from area to area. If they are shipped in a
carton,
they must be in the original carton or
one of equivalent strength, and securely
sealed
to prevent accidental opening. Also,
3279 MIM
Figure 4
d. Repeat this cycle once every five
seconds until the victim breathes
for
himself or medical help arrives.
Reporting Accidents
It is aCE's responsibility to report all electrical
accidents, potential electrical hazards, and
"near
miss" accidents to your field manager.
Remember, a linear miss!! accident might be the
result of a design deficiency and prompt
reporting will ensure that the situation will be
resolved quickly.
It's important to report even a minor shock
since the conditions
which caused it need only
be varied slightly to cause serious injury.
original
or equivalent packing materials
and/ or forms must be placed inside the
carton
to give the tube proper support and
protection.
If tubes are transported in a unit
or piece of equipment, the equipment must
be able to contain the glass fragments
should an implosion occur.
2. CRTs should be stacked as per directions on
manufacturer's carton.
When in doubt, stack
with faceplate (viewing surface) down.
Cartons should not be stacked more than
two high.
3. CRT storage areas will be away from normal
flow of material handling equipment and
pedestrian
traffic. Also, storage areas must
be dry to insure that cartons will not absorb
moisture and collapse.
ix

3279 MIM
Maintenance and Installation
1. No one shall be permitted to install, adjust,
maintain, replace, or handle high-vacuum
tubes until he has reviewed this CEM.
2. Cathode Ray Tubes when received,
transported, or otherwise moved from area
to area should be completely enclosed in
their original shipping carton and sealed.
3. When handling CRTs, personnel will wear
safety equipment at all times. The required
safety equipment is:
a. Safety Glasses -IBM Part 5715010
b. Long-Sleeved Garment.
4. Tubes und<;>r vacuum will not be permitted to
remain out of their carton unless they are
under
test or inspection.
5.
Avoid scratching or bumping any part of the
tube because this may weaken the glass and
possibly cause it to implode.
6. Prior
to removal of any high-vacuum tube,
discharge all stored potential which may
exist on the tube's anode button or base
socket pins and the capacitor in the
high-voltage supply. (NOTE: Some Cathode
Ray Tubes
contain a conductive coating on
both the inside and outside surfaces to form a
capacitor. Within some tubes, a second
capacitive charge builds up following the
original discharge. It is therefore important to
discharge each tube a second time
immediately before removal.)
7. Do not handle Cathode Ray Tubes by the
neck alone. The neck is the
weakest part of
the tube and is easily broken. Always
handle tubes with two hands. If the CRT is
shipped
with a lifting strap, this strap should
be used
for the removal of a tube from, and
placement
of a tube into, the shipping
container.
8. When inserting or removing tubes from
equipment, they must be supported by the
large end while carefully guiding the neck in
or out of position. The lifting strap, if
present, can be used in this process.
9. Avoid placing the tubes on a table or bench
when there is any possibility of the tube
rolling. If it is necessary to place a tube
anywhere except in its special carton, a
piece
of felt or other soft material should be
placed under
it to prevent scratching the
glass. Place larger tubes vertically on their
faces, and not on their sides, to prevent the
possibility of rolling.
10.
When removing a tube from equipment, it
should be enclosed in its shipping container
as soon as
possible to reduce the chances
of breaking. Cathode Ray Tubes should be
placed in the carton
with the large face end
up and the neck down. Be sure that the
weight of the tube is not resting on the
neck. The container should be sealed
securely
with strong tape and, to prevent
tipping, turned over so the tube is
positioned face down.
Disanning Cathode Ray Tubes
x
Field personnel should not disarm Cathode Ray
Tubes. Tubes
will be disarmed and disposed of
in accordance with existing Environmental
Protection Agency requirements at the plant of
return.
Disposal of Cathode Ray Tubes
An Inventory/Distribution letter has been issued
to the Branch Office with instructions on the
disposal of CRTs.
July 14, 1980

Chapter 1. General Description and
Locations
1.1 Introduction
The IBM 3279 Color Display Sfation is connected
by a coaxial cable to the IBM :1274 Control Unit,
or the IBM 3276 Control Unit/Display Station, or
an Integrated Display Printer Adapter (IDPA)
processor. The 3279 Display Station consists of a
color display
unit and an alphanumeric keyboard.
Four models of 3279 are available; 2A, 2B, 3A and
3B. Model 2 has 24 lines, each of 80 characters;
Model 3 has
32 lines, each of 80 characters. An
additional model 3279-2C is available as a
system-control console. see
IBM 3279 Model 2C
Color Display Console Maintenance Information ..
SY33-0090. Models with an A-suffix can display
four colors. Models with a B-suffix have
highlighting and 7-color capability
(ECS) and an
additional font for
APL/Text. Note that the 3276
Control Unit does not support models with a
B-suffix,
and that the IDPA supports only the
model2A.
Optional features include a selector light pen, a
security keylock, and magnetic reader control (for
slot reader or
hand scanner). Programmed symbols
(PS2-two fonts, and PS4-four additional fonts) is
an optional feature on model 3B.
Machines are available
to operate from an ac supply
of either 100 to 127 V (SO or 60 Hz) or 200 to
240 V (50 or 60 Hz). A battery is used to enable
storage to retain convergence data when switched
off.
1.1.1 COli trois
1.1.1.1 Power On/Off Switch
This switch controls line voltage. Wait
approximately 10 seconds after switching off before
switching on again. This allows any stored fault
conditions
to reset.
1.1.1.2 NormallTest Switch
This switch when' operated takes the machine
offline
and into Test Mode.
Indicator '~i iNormal/Test
(Power Onl 0 Switch
Indicator 2.~ r-"(-=============-::, Q Base Color
(Display Ready) •• Switch (oooo/col
Indicator 3 I ea Dualcase/Monocase
ITestl ~ I Switch IAaAI
:::~:::/~~:----~ I--~-, -++-----'" ~~~~~~: ~~~:Ol
Switch -------!-.... ___ ~~L._______ .J.---arightness Control
\ '-- ." .-/ • ) and Intensity Override
Operator , ~ Switch
Information Area '-"----r-7---::=====;:-=---------r:::--
V, -r@A)h_securitYKeYIOCk
Voltage Rating ------- 1... ____ ~_:;;.?-:..---------..JJ-
Plate
Mainline Fuse -----------
Figure 1-1. Controls and Indicators
3279 MIM Chapter I. General Description and Location 1-1

3279 MLM
1.1.1.3 Base Color Switch
When this switch
is in the '00' position, the base
colors blue and red are replaced by green and white
respectively. The separator line and the operator
information area remain blue. Green and white
fields are not affected, nor arc any fields controlled,
by ECS.
1.1.1.4 Dualcase/Monocase Switch
When this switch is in the 'A' position, all
alphabetic characters are displayed
in uppercase.
1.1.1.5 Intensity Override Switch
This switch operates when the brightness control is
turned fully counterclockwise. It sets the brightness
circuits to maximum and the screen shows fuU
rasters of red, blue, and green. See section 2.4 for
details.
1.1.1.6 Audible Alarm Volume Control
This control sets the volume of the alarm.
1.1.1.7 Brightness Control
This control sets the brightness of the display.
1.1.1.8 Security Keylock
When in operation, this feature blanks the data area
of the screen to prevent unauthorized access to the
machine.
1.1.2 Indicators
1.1.2.1 Indicator I (Power On)
This indicates line supply and +5 V supply
available.
It does not confirm the availability of
other voltages generated within the machine.
1.1.2.2 Indicator 2 (Display Ready)
This indicator lights when the display
is unblanked,
thus confirming that most of the analog circuits are
operational. This condition occurs about 45 seconds
after both deflection circuits are activated. The
delay allows the CRT cathode time to warm up.
1.1.2.3 Indicator 3 (Test)
Indicator 3 Lights when Test Mode
is selected.
1.1.2.4 Operator Information Area
The Operator Information Area is the row below
the separator line, and displays characters that
indicate the status of the 3279.
Chapter
1. General Description and Location
1.2 Display Unit
The display unit comprises a main enclosure
assembly, a logic gate, and a b~zel as shown in
Figure 1-5. Field Repl""eable Units (FRUs) are
listed
in the Parts Catalog.
The weight of the unit
is approximately 27 Kg
(58 lb) without keyboard.
1.2.1 Electrical Grounding
1-2
The ac ground and de returns are electrically
connected in the 3279 display unit. The coaxial
cable return (shield)
is isolated from the dc return
at the 3279.
With the ac power cord disconnected, a
correctly-wired unit should indicate continuity
between ac and de ground, and an open circuit
between ground and the shield of the device coaxial
cable.
See Figure 6-5 for a complete grounding diagram.
1.2.2 Equipment Lightning Protection
The 3279 is designed to provide a low-impedance
energy path from the external coaxial cable shield
to frame (ac) ground for potentials above 36
V.
Additional information on lightning protection
requirements for the customer coaxial cable
(customer responsibility)
is provided in IBM 3270
Information Display Station Installation Manual -
Physical Planning. GA27-2787.
1.2.3 Video Output Facility
This allows suitable monitors to display the contents
of the 3279 screen (except for the separator line
and Operator Information Area).
Red Video, Green Video. Blue Video and Sync
signals are fed to individual coaxial sockets in the
customer access area.
A sync polarity indicator and two switches (video
control switch and sync polarity switch) are
also-
provided in the customer access area.

1.2.3.1 Video Control Stritch
This switch has three positions:
1. Central position: The monitor receives the same
balance of color signals
as the 3279 CRT.
2. ENHANCE position: The blue color of the
monitor is brightened by the addition of a
fifty-percent-green signal.
3. TEST position: The color signals to the monitor
are internally connected to the 3279 CRT, thus
allowing direct comparison of the two displays
(except for the separator line and Operator
Information Area).
1.2.3.2 Sync Polarity Stritcb
This switch is used to select either positive or
negative sync pulses at the sync output socket.
All
devices attached at the same time will receive the
same polarity.
1.2.3.3
SIgDaI Test Indicator
This indicator lights when either
• The synchronizing signal is faulty,
or
• The Video Control Switch is set to TEST.
3279MfM
Chapter 1. General De8o;riptil>n and Location

3279 MlM Chapter 1. General Description and Loclltion
* DANGER
Pins may be-up to 250 V above ground potential
Use probe, IBM Part 1749249/1749250.
Skip
Skip.
Vertical Sync
-5V
Gnd from A3
+12 V LOPT
-Display Ready
3
4
5
6
7
*1
8
9
10
11
12
13
14
15
16
P3
+12 V
±12 V Retum
-12 V
103 V Return
103 V
Ground
Ground
LOPT
.lOPT Return
Line Input
• Line
Test Point
Degauss
Degauss Return
• - Neutral Test Po-int
Neutral Input
Ground
Test Points are shown
as bullets ( • )
Power
Supply
Edge Connector -------,
Pin Assignments
~~~ Securing , ___ ---..
Degauss COil
P12-----~~~
-Display Ready
+5V
+8.5 V
+8.5 V •
+5 V •
Gnd •
+103 V •
Brightness Pot
Intensity Override Sw 4
Intensity Override Sw 1
Brightness 2 To Color Balance
-135 V •
+6.3 V Return •
+70 V •
+6.3 V •
Figure 1-2. Display Unit - Front View with Bezel Removed
26 Horizontal Sync
27 • Hariz Sync
28 3 • Vert Sync
29 4 oV
form A3
30 5 •
-5 V
31 6 o V
to security key lock
32 7 oV to Color Sw
33 8
34 9 oV
to A,af A Switch
35
l)
oV to LED Card
36
11
37 12
"Power Good" (+5 VI
38 13
Input Prohibited
39 14 +103 V Return
40
15 +103 V
41
16 Brightness 3
42 17 Brightness 1
43 18 Intensity Override Sw 2
44 19 Brightness 2
45 20 Balance Pots Ret
(-150 V/39
46
21
47 22 Heater (6.3
V) Return
48 23
+70 V to Video
49 24
+70 V Return
50 25 Heater (+6.3
VI
P4
Analog Card
Edge
Connector
Pin Assignments
1-4
kUI

Top Card Connector
Identification
Internal Cabling
A2 to power supply card
A3 to the enclosure
A5 to amplifier and video cards
05 to keyboard connector
Card Socket
Identification
G2 to G4f
crossovers for M RC
G3 to G5
Figure 1-3. Display Unit -Rear View
3279 MIM
For logic card locations,
see Figure 1-6
Sync
Polarity
Switch
Signal Test Video Sync Red Green
Lamp Control ,
Switch
Output
Sockets
I
Video Output Facility
Chapter 1. General Description and Location 1-5
Blue
,

3279 MIM Chapter 1. General Description and Location
\-6
Analog Card
**
Amplifier Card Test Points
(see Figure 6-11) Power Supply Card ***
, View hole for
CRT filament
Jumper
o HCENT
(J)Q:.~:PURITyA
oSTATIC
BLAT0B~} 4BLAT
G0R~ GAIN*
MIN ~ 0 Q}COLOR N
MAX ~ ~ S BALANCE
PI? All 1011 alpl?S
I
(
In'
\" ~p'4
I' •
\ 1'1'2
L."'.l_
*** Two ground wires Video Card
(for Test Points,
see Figure 6·10)
* Factory preset (some presets are only on early level cards)
** Four Static Convergence Controls
* ** DANGER Ensure the insulated covers are in place on any
transistor in these two positions as the cases are at dangerous
potentials (1 kVpkl
Figure \-4. Display Unit -Rear View, Open
Convergence and Purity
Coil Assembly

Cathode Ray
Tube & Coil
Assembly
Bezel
CRT
Label
Main
Enclosure
Assembly
Audible
Alarm
EHT
Connection
Deflection
Coils
EHT Bleed
Assembly
Amplifier
Card
Top Card
Connector
Analog
Card
Convergence
IPurity Coil
Assembly
Grounding
Plate
Video
Card
Logic Gate
Power Supply
Card
Figure 1-5. Display Unit -Interior View
3279 MIM Chapter
1. General Description and Location 1-7

3279 MIM
For jumpers, use assembly as shown
j
~ Pon 453443:-\
/ Lpan 452655~ \
..bcSIa:=! !==CIIIIa~
BCD E F
Chapter I. General Description and Location
G H
i<
TOP CARD CONNECTOR LA YO
BY MODEL AND FEATURE
Model A Model B with
PS
1-8
220' 02
~
D2·E2 D2·E2·F2
33, ,13
Pin assignments
3
4
*Feature
**Model B only
Notes:
o w
.~ u
.:: -+--+--- "'- -- ~-
~ it a:
'" i<
~i<
u
"0
~
• .c
§,
x
~
~
til
"0
~
~
i< Y
22
0 c
0:
~
a.
.c
0>
.J
§ Z
Top Card Id:ntlflcatlon J 33
1. If Video Output Facility is installed, line control card is replaced by video output card.
2. Mlhen installing Top Card Connectors ensure that the longer (curved) pins are plugged
into the card and the partnumber reads from top to bottom. Check that the cover and
label have been installed correctly.
Figure 1-6. Logic Card and Top Card Connector Locations (card side)·
C3·D3 C3·D3 C3·D3
E3·F3
C4·D4 C4·D4 C4·D4
C5·D5
~-----L ____ i---~-"

1.3 Keyboards
1.3.1 Scan Codes
Pressing a key generates a seven-bit scan code that
is presented serially to the control unit. The scan
code for a specific key position is a1ways the same.
The control unit translates each scan code into the
appropriate character or function.
1.3.2 Break Codes
Several keys, including the reset key, produce a
second scan code (called a
'break code') as the key
is released. The break code for the reset key is
ignored by the control unit.
1.3.3 Keyboard Cable
This cable carries the control and data signals
between the keyboard and the display unit. It also
provides the
+5 V supply for the keyboard (see
Figure 6-12 for details).
1.3.4 System Upshift
System upshift cannot be selected from the
keyboard; it is controlled by the application program
and applies to all keyboard types. When the system
is in upshift mode, the control unit (3274 or 3276),
or IDPA, processes only specified characters.
Characters other than those specified may be
entered by an operator using the override capability.
1.3.5 Keyboard Type Identification
The keyboard logic card contains four pairs of pins
that must be jumpered to indicate the type of
keyboard (see Figure
6-11).
1.3.6 Keyboard Lock
The keyboard can be 'locked' (that is, keyed
characters are ignored by the control unit). Specific
data, for example a 'reset' scan code, may still be
accepted.
The operator is made aware of keyboard lock by a
change in
the action of the keyboard clicker. The
clicker normally clicks once for each key depression,
but stops clicking after keyboard lock. If the
operator has chosen to turn off the clicker for
normal operation, then- keyboard lock will cause it
to click at each key depression.
An )( is displayed in the Operator Information
Area when the keyboard is locked.
3279 MIM
1.3.7 Numeric Lock (Feature)
The numeric lock feature is selected by installing a
keyboard jumper in position 1 of the keyboard 1D
jumper block. This feature limits the characters
that can be entered into a numeric field to:
othrough 9
period
(.) or comma (,)
minus
(-)
The DUP key remains active. Depression of any
other key while the cursor is in a numeric field
causes the keyboard to lock with the symbol
)( *NUM in the operator infonnation area.
Press
RESET to clear the locked condition.
1.4 Tools and Test Equipment
The following tools and test equipment are required
for maintenance of the 3279.
Item
Insulated probes·
General logic probe
Miniprobe**
GLP extension cable
Keytop puller
Keylock retaining nut wrench
MR C test card
SLT jumper (3)
SLT pins···
Adjusting tool
Metric tools
Alignment mask
Isopropyl Alcohol
Lint-free cloth
IBM Part
Number
1749249
and
1749250
453212
453718
453605
9900373
4418787
1742659
452655
453443
1864853
1749235
4423472
2200200
2108930
For use with standard CE meter
This probe
is for use on low voltage
(up to 15 volts)
For use with jumpers on some top
card connectors
Chapter 1. General Description and Location 1-9