•s^r

. .. Ifga

■ '■ ■•• 3; ' • i

/fif

TOW

P; : :'-^V'-:

£3&*J

iris

*>i#r

r#?

r{&

*&j&sip:g t ifc :

. ••'... '• '".'*?* X" '• : .,' -j/*,' V

:-■ / • ' ■ -' : X. .. . "'

r...:,.::. x,... .x;X;,/; ■’ .

*■"■ Ir t 1 - v3j ^ lir " rnB " 1 :-y^ i-

' ' "V-'.yv.-V ,-

?

• •’ , * •• ^ • - - > -

., ■ -'. ,

v-'••■'.•> -...vT.•■’;'■-;■• .Wv • . '" .: i • .••■ -• y- V*'-;

v '.*mm ■ ■ ■

yyy

* 1 ^

• jj- ' ;■ ' •: -

.', . ;■

.. ....... ..

•'-' V ^■ .Cv-: •.. l h■ v.o- >-

mmm

.... . . ^ ■ 1> : -
5' •••'■• *
' ... ; - *-

#«:?

:^r:-r v ‘.-- -v/- V;: :Z7.-Z$t*

ATARI HOME COMPUTER

FIELD SERVICE

MANUAL

4 0 0/S 0 0

TABLE OF CONTENTS

Section Title p age

INTRODUCTION. be

1 THEORY OF OPERATION . 1-1

Overview. 1_1

User Interface. 1_2

400/800 Mechanical Description. 1-3

Motherboard. 1_4

Central Processing Unit. 1-5

ROM Personality PCB. 1-5

RAM PCB. 1_5

Keyboard. i-$

Power Supply. 1_6

Program Cartridge. 1-6

400/800 Electronic Discussion .. 1-7

Central Processing Unit. 1-7

CPU 6502 Integrated Circuit .. 1-7

Alphanumerical Television .. 1-8

Interface Controller

Color Television Interface.1-10

Adaptor

Graphic Television Interface.1-10

Adaptor

I/O Decoder. 1«10

Composite Video..

Motherboard Console - 400 . 1-11

Pot Keyboard Integrated.1-11

Peripheral Interface Adaptor.1-11

Key-In Key-Out Integrated.1-12

Circuit

Memory Map Decoder. 1-12

I/O Decoder. 1_13

Motherboard Console - 800 .1-14

Bi-directional Data Buffer .1-14

ROM Personality Board.1-15

Power Supply..

ROM Cartridge. 1_17

Accessories..

AC Power Adaptor..1-17

TV Switch Box.1-17

'BASIC' Program Cartridge.1-17

2 SILKSCREEN AND SCHEMATICS. 2-1

3 TROUBLESHOOTING AND TESTING. 3-1

Overview. 3_1

Tests. 3_1

Equipment Needed. 3-1

Testing With and Without. 3-2

the SALT II Cartridge

ATARI Home Computer

iii

TABLE OF CONTENTS (Cont)

Section Title Page

Overview of Tests. 3-2

Power-Up Test. 3-2

Keyboard Test. 3-2

RAM and ROM Test. 3-2

SALT II Menu. 3-5

Color Bar Test. 3-6

Any Video Test...'. 3-7

Gray Bar Test .. 3-8

Keyboard Test. 3-9

Switch Test. 3-9

Tone Test. 3-9

Display Options.3-10

Port Test.3-10

Verify ROM Test.3-11

RAM Test.3-12

Shake Test.3-16

Burnin. 3-16

Description of the Other Functions.3-17

Production Test.3-17

Boot B. 3-17

Examine.3-17

Adjust.3-17

Summary . 3-17

4 DISASSEMBLY/ASSEMBLY MAINTENANCE. 4-1

ATARI 400 Home Computer Console - Disassembly. 4-1

Keyboard and Power Supply Access. 4-1

Keyboard Removal. 4-3

Power Supply Removal. 4-4

CPU, RAM and Motherboard Access. 4-6

CPU and RAM Removal. 4-6

ATARI 800 Home Computer Console - Disassembly. 4-8

Access to RAM Boards and. 4-8

ROM Board

Access to Power Supply and. 4-9

Keyboard Assembly

Remove Top Cover .. 4-9

Remove the PCB Module.4-10

Remove the Power Supply.4-11

Access to CPU Printed Circuit Board.4-12

Access to Motherboard .4-13

Keyboard Removal.4-14

ATARI Home Computer

iv

TABLE OF CONTENTS (Cont)

Section

^ 5

6

7

8

9

Title

Page

ATARI WO Home Computer Console - Assembly

Module Assembly Reassembly...

Keyboard Installation...

Power Supply Installation.

Top Cover Installation ..

ATARI 800 Home Computer Console - Assembly

Keyboard Assembly .

Motherboard Installation..

CPU PCB Installation.

Power Supply Installation.

Module Assembly Installation into Top Cover

Bottom Cover Installation..

RAM and ROM Installation ...............

Cartridge Door Assembly.

PCB Contact Cleaning and Lubricating.

Tools Required .

Procedure.

Visual Inspection..

4-15
4-15
4-16
4-16
4-17
4-17
4-17
4-17
4-18
4-18
4-19
4-19
4-20
4-20
4-20
4-20
4-21
4-21

400 DIAGNOSTIC FLOWCHARTS
400/800 SYMPTOM CHECKLIST ,
800 DIAGOSTIC FLOWCHARTS.,
GAME CONTROLLERS.

Joystick (X-Y Controller)..

Joystick (X-Y Controller) Check

Equipment Needed.

Procedure.

Game Paddle.

Game Paddle Controller Check

Equipment Needed.

Procedure.

8-1

8-3

8-3

8-3

8-4

8-5

8-5

8-5

PARTS LIST

10

400 Computer.

800 Computer.

SERVICE BULLETINS

ATARI Home Computer

v

LIST OF ILLUSTRATION

Figure Title Page

1-1 ATARI 400 Home Computer Console. 1-1

1-2 ATARI 800 Home Computer Console. 1-2

1-3 MPU Pin Assignments . 1-8

1-4 ANTIC Pin Assignments. 1-9

1-5 CTIA/GTIA Pin Assignments..1-10

1-6 POKEY Pin Assignments.1-11

1-7 PI A Pin Assignments. 1-12

1-8 400 Motherboard Flow Diagram.1-18

1-9 400 Power Supply .1-19

1-10 800 Motherboard Flow Diagram.1-20

1-11 800 Power Supply Flow Diagram .1-21

1-12 800 Personality Board..1-22

1-13 CPU Board Flow Diagram...1-23

1-14 8K Dynamic RAM Flow Diagram.1-24

1-15 16K Dynamic RAM Flow Diagram.1-25

1-16 Game Cartridge Flow Diagram....1-26

1- 17 ATARI Home Computer System.1-27

Block Diagram

2- 1 400 Motherboard Silkscreen. 2-3

2-2 400 Motherboard Schematic. 2-4

2-3 400 Power Supply Silkscreen. 2-6

2-4 400 Power Supply Schematic. 2-7

2-5 800 Motherboard Silkscreen. 2-9

2-6 800 Motherboard Schematic.2-10

2-7 800 Power Supply Silkscreen.2-12

2-8 800 Power Supply Schematic.2-13

2-9 800 Personality Board Silkscreen.2-14

2-10 800 Personality Board Schematic.2-15

2-11 CPU Board Silkscreen .2-16

2-12 CPU Board Schematic.2-17

2-13 8K RAM Board Silkscreen.2-18

2-14 8K RAM Board Schematic.2-19

2-15 16K RAM Board Silkscreen.2-20

2- 16 16K RAM Board Schematic...2-21

3- 1 Special Graphics Test. 3-3

3-2 SALT Header. 3-4

3-3 SALT II Menu. 3-5

3-4 Color Bar Test Screen... 3-6

3-5 Any Video Test Screen. 3-7

3-6 Gray Bar Test Screen. 3-8

3-7 Port Test Screen...3-10

3-8 RAM TEST Screen .3-13

ATARI Home Computer

vi

LIST OF ILLUSTRATION (Cont)

Fig*™ Title Page

4-1 ATARI 400 Console, Bottom Cover Screw Location ....... 4-2

4-2 ATARI 400 Console, Top Cover Removal... 4-3

4-3 ATARI 400 Console, Keyboard Removal. 4-4

4-4 ATARI 400 Console, Power Supply Removal .. 4-5

4-5 ATARI 400 Console, Module Assembly. 4-7

4-6 ATARI 800 Console, Cartridge Door -. 4-9

Assembly Removal

4-7 ATARI 800 Console, Bottom Cover Removal.4-10

4-2 ATARI 800 Console, Module Assembly Removal.4-11

4-9 ATARI 800 Console, Power Supply Removal .............4-12

4-10 ATARI 800 Console, CPU Printed Circuit - ..4-13

Board Removal

4-11 ATARI 800 Console, Motherboard Removal ..4-15

4-12 ATARI 800 Console, Keyboard Removal..4-15

3-1 Keyboard Connection Chart..

3-2 Defective RAM Boards..

7-1 Keyboard Connection Chart. 7-38

7-2 Defective RAM Boards. 7-39

2-1 Joystick (X-Y Controller). 8-2

2-2 Joystick Schematic. 8-3

2-3 Game Paddle. 8-4

2-4 Game Paddle Schematic. 8-5

LIST OF TABLES

Table Title Page

1-1 Memory Map Selected Lines. 1-13

1-2 I/O Decoder Select Line . 1-14

3-1 Port Test Legend . 3_12

3-2 Defective RAM Boards . 3-14

3-3 Defective RAM Identified.3-15

5-1 Clock Circuit..

5-2 Defective RAM Boards .5-39

5-3 Port Test Legend ..

7-1 Clock Circuit..

7-2 Defective RAM Boards .7-39

7-3 Port Test Legend .7-40

ATARI Home Computer

vii

INTRODUCTION

Jp* e ATARI 400/800 Home Computer Field Service Manual is organized in 10
Sections:

1 THEORY OF OPERATION - overview of how the 400 and 800 Home
Computers work.

2 SILK5CREEN5 AND SCHEMATICS - electrical layouts and drawings for
major components.

3 TESTING AND TROUBLESHOOTING - overview of tests which assist in
diagnosing malfunctions.

4 DISASSEMBLY/ASSEMBLY - detailed instructions to completely

disassemble and assemble both units.

5 400 DIAGNOSTIC FLOWCHARTS - detailed procedures for

troubleshooting and repairing the 400 Computer.

6 400/800 SYMPTOM CHECKLIST - quick reference for troubleshooting
each computer.

7 800 DIAGNOSTIC FLOWCHART - detailed procedures for

troubleshooting and repairing the 800 Computer.

8 GAME CONTROLLERS - overview of hand controller construction and
recommended test procedures*

9 PARTS LIST - detailed breakdown of all parts used in each unit.

10 SERVICE BULLETINS - section to be used to hold Field Change Orders,
Upgrade Bulletins, and Tech Tips.

This manual is designed for use by both the experienced and inexperienced service
technician. The Diagnostic Flowcharts (Sections 5 and 7) provide detailed
repair P rocedures for technicians not completely familiar with the
ATARI 400/800 Home Computers. The Symptom Checklist (Section 6) provides a
rapid repair reference for the more experienced technician.

ATARI Home Computer

ix

SECTION I

THEORY OF OPERATION

OVERVIEW

The Atari 400 Computer Home Console contains the central processor unit (CPU) and
memory in the form of the Operating System (read-only-memory (ROM)) and 8K or
16K of user programmable random access memory (RAM). The console contains the
keyboard, cartridge slot, controller jacks, and serial input/output (I/O) port for
connecting peripheral devices (see Figure 1-1).

ATARI Home Computers

1-1

The ATARI 800 Home Computer Console contains the CPU and memory In the form of
the Operating System (10K of read-only-memory (ROM)) and 8K to 16K (standard) of
user programmable random access memory (RAM); plus two expansion sockets for
additional RAM modules (maximum 48K). The console also contains the keyboard,
cartridge slots (2), controller jacks and a serial I/O port for connecting peripheral
devices (see Figure 1-2).

POWER JACK

Figure 1-2. ATARI 800 Home Computer Console

USER INTERFACE

The ATARI 400/800 Home Computer Consoles are general purpose microcomputers
using the 6502 microprocessor. The ATARI 400/800 Consoles are the central
processing units for their respective systems. Each console comes standard with a
built-in typewriter style keyboard, 8K/16K of RAM, ROM operating systems,
connector jacks for adding peripherals and hand controllers, and a 15-foot Radio
Frequency (RF) cable for connection to the user's television set.

The controller jacks on the front of both consoles accepts the X-Y (joystick) and
paddle hand controllers available from ATARI.

ATARI Home Computers

1-2

The ng '?M / S i d * panel ° f the Atari 400 Computer Console contains a peripheral jack,
power ON/OFF switch, and a power jack. The channel 2/3 switch is located on the
back of the console. This switch changes the console transmission frequency to either
channel 2 or channel 3 (refer to Figure 1-1). y

The right side panel of the Atari 800 Home Console contains a monitor jack, a
toFigu^l J -2) k ’ a Channel 2/3 Switch ’ a power ON /° FF sw itch, and a power jack (refer

Both Console keyboards provide a full alphanumeric character set, cursor controls, and
purpose keys. The alpha keys when used in conjunction with the Control
S5 L key become special graphic symbols. To the right of the keyboard is the power
ON light and four special control keys (refer to Figure 1-1 and Figure 1-2).

From the top to the bottom they are:

SYSTEM RESET -
OPTION

SELECT

START

Interrupts whatever the computer is doing and restarts the
Operating System or Program Cartridge.

Interrupt used by the Program Cartridge to choose among
the variations within a game or program.

Interrupt used to select one of several games or programs
on the Program Cartridge.

Interrupt used to Start the game or program selected from
the Program Cartridge.

400/800 MECHANICAL DESCRIPTION

modulesthe°^are^ C ° mpUter Home ConsoIes are made up of seven major functional

• Motherboard

• Central Processing Unit (CPU) Printed Circuit Board

• ROM Personality Printed Circuit Board (Operation System) (800 Only)

• RAM Printed Circuit Board(s)

• Keyboard

• Power Supply Board

• Program Cartridge

ATARI Home Computers

1-3

The Printed Circuit Boards (PCBs) plug into sockets on the motherboard, using a
common Address Bus, Data Bus and clock lines. The various power requirements are
routed from the power supply through the motherboard to all printed circuit boards.

The keyboard connects directly to the motherboard through a ribbon connector. The
sixteen-line Address Bus allows the microprocessor to directly address 64K of memory.
The eight-line Data Bus provides the communication and data path between the
functional modules.

Figures 1-8 thru 1-17 at the end of this section provide function block diagrams of
PCBs in the 400/800 systems.

Motherboard

The motherboard ties all components of the computer system together. It also
performs a variety of logic functions. All PCBs and connector cables plug into the
motherboard and allow communication between the functional blocks of the 400 and
800 Computer Consoles. The motherboard also performs the following:

• Generates a 3.58 MHz master clock for the Central Processing Unit's PCB.

• Generates the Power-ON RESET for the Central Processing Unit PCB and
the peripherals.

• Provides the driving circuitry for the Key-Press signal from the Central
Processing Unit PCB to the Console speaker.

• Converts signals from the various hand controllers into recognizable data
for the microprocessor.

• Buffers and drives the data lines between the Central Processing Unit PCB,
the RAM PCBs, and the remainder of the system.

• Does the first memory map decoding of the possible 64K address locations
into 8K blocks for the microprocessor.

• Generates control signals for the peripheral devices.

• Receives video data from the Central Processing Unit PCB, converts it
into a composite video and routes it to the power supply PCB.

• Combines the sound from the Computer system and the audio track of
prerecorded cassettes.

• Develops the sound subcarrier for the television audio as part of the
composite video.

ATARI Home Computers

1-4

Central Processing Unit

The Central Processing Unit (CPU) PCB is the controller of the entire Console system.

CPUPCB contains the 6502 microprocessor, and the ANTIC and CTIA (or GTIA)
chips* The CPU PCB controls the Console system and its peripheral devices through
address lines (to select which device it needs to communicate with) and data lines (to
transmit and/or receive data from a selected device) common to the entire system.
Operating instructions for the microprocessor come from the ROM Operating System
on the Personality PCB. Additional functions of the CPU PCB are:

• Receives the master clock from the motherboard and generates Phase 1 (/I

or Ph l) and Phase 2 2 or Ph 2) clocks used to synchronize the entire

system.

• Transmits a REFRESH signal at least every 2 miliseconds to refresh the
dynamic RAM chips on the RAM PCB(s).

• Receives the four TRIGGER lines from the fire button on each of the hand
controller accessories.

• Receives the lines from the four control switches located to the right of
the keyboard.

• Generates video signals to be processed by the motherboard before they
are sent to the RF module on the Power Supply PCB.

ROM Personality PCB

The ROM Personality PCB contains information in Read-Only Memory (ROM), the
program of operating instructions for the microprocessor. Two 4K ROMs contain the
Operating System, and one 2K ROM contains the arithmatic functions used for BASIC
programming. Information is retrieved from the ROMs by addressing a particular
location on the ROM using the Address Bus. The data contained at that location is
placed on the Data Bus to be read by the microprocessor.

The ROM Personality PCB also provides the CHIP SELECT signals used to select LSI
chips throughout the Console system and for the bi-directional data buffers on the
motherboard.

RAM PCB

The Random Access Memory (RAM) PCB performs the function of temporary data
storage for the system. The RAM is dynamic, requiring REFRESH, and is available in
8 K or 16K versions.

Each RAM chip on the RAM PCB has only seven address lines. To address 16K
locations requires 14 address lines. To accomplish this, a 14-bit address is

ATARI Home Computers

1-5

sent to the address demultiplexer, which first passes the lower seven bits to the RAM
chips as a Row Address. After an appropriate delay, the highest seven bits are passed
as a Column Address. Data is then either put into or taken out of the location
selected. The direction of data flow is determined by the Read/Write line.

REFRESH occurs at least every two milliseconds. The REFRESH signal is generated
on the CPU Board.

Keyboard

The typewriter-style keyboard is used to generate alphanumeric characters as well as
special graphic symbols. The keyboard allows the operator to communicate with the
console system for writing programs or responding to preprogrammed cassettes or
cartridges. The keyboard consists of 57 normally open switches. The switches are
scanned at a rapid rate and when a switch is found closed, that scan pattern is sent to
the Pot Keyboard Integrated Circuit (POKEY) for encoding.

Power Supoly

The Power Supply PCB receives 9 VAC from an external power adaptor (transformer)
and provides +5Vdc, +12Vdc, and -5Vdc for the Console system. The Power ON/OFF
switch is mounted on the Power Supply PCB and removes input power by opening the
9Vac lines. An interlock switch breaks power to the system when the operator opens
the top panel of the Console to install or remove Program Cartridges.

The RF Module resides on the Power Supply PCB. The RF Module generates the RF
output for the video screen from the composite video signals received from the
motherboard, and is switchable to television channel 2 or 3.

Voltages:

+5Vdc A - Supply voltage for the logic PCBs.

+5Vdc B - Specially filtered for the video circuitry.

+12Vdc and -5Vdc - Supply voltage for the dynamic RAM chips.

Program Cartridge

The Program Cartridge permanently stores the microprocessor instructions for a
particular application. It consists of two 4K ROM chips mounted on the enclosed PCB.
Information is received from the ROM chips by addressing the memory locations
assigned to the Program Cartridge slot(s). Data in the memory locations is then
placed on the Data Bus lines.

ATARI Home Computers

1-6

400/300 ELECTRONIC DISCUSSION

The remainder of this section provides a detailed discussion of the functions of the
seven major modules.

Central Processing Unit

The Central Processing Unit (CPU) PCB contains the 6502 CPU (or MPU) chip (A303)
the CTIA or GTIA chip (A301), the ANTIC chip (A302), tri-level address buffers (Z303
and Z304), and the clock generator (Z302A and Z302B).

CPU 6502 Integrated Circuit

The 6502 microprocessor contains register flags, interconnections, arithmetic logic,
and control logic, all recognized operation codes. The characteristics of the 6502
microprocessor are:

• Byte-oriented structure

• 151 opcodes

• Decimal and binary arithmetic modes

• Seven addressing modes

• True indexing

• Stack pointer

• Two interrupt levels

• 64K address range

• Integral clock circuit

• Single +5 volt dc power requirement

Fugur-e 1-3 is an illustration of the 6502 pin assignments. The functions of the pins are
explained on the following pages.

ATARI Home Computers

1-7

VS5

C

1

40

□

RES

RDY

c

2

33

□

h

h

c

3

3S

SO

IRQ

c

4

37

□

Jo (IN)

N.C.

c

3

36

□

N.C.

TwT

c

6

33

3

N.C.

YNC

c

7

34

□

R/W

vcc

c

S

33

□

D#

A#

t

3

32

□

Dl

A1

c

MCS6302

31

□

02

A2 *

c

11

30

□

D3

A3

c

23

□

D4

A4

c

13

2S

□

D3

A3

c

14

27

□

D6

AS

c

13

26

n

D7

A7

n

16

23

□.

AI2

AS

c

17

24

3

A13

A3

c

IS

23

3

A14

AIO *

c

13

22

3

A13

All

c

20

•

21

3

VSS

Figure 1-3. MPU Pin Assignments

Alphanumeric Television Interface Controller

The primary function of the Alphanumeric Television Interface Controller (ANTIC)
chip is to fetch data from memory, independent of the processor, for display on the
video screen.

Figure 1-4 is an illustration of ANTIC Pin Assignments.

ATARI Home Computers

1-8

GROUND

VSS

CTIA Data

ANj0

CTIA Data

AN!

Light Pen

CP

CTIA Data

AN2

Interrupt Input

RNM1

Interrupt Output

NM1

Refresh

REF

HALT

HALT

Address Bus

A3

Address Bus

A2

Address Bus

A1

Address Bus

A0

Read/Write

R/W

Ready

RDY

Address Bus

A10

Address Bus

A12

Address Bus

A13

Address Bus

A14

Address Bus

A15

1

•

40

D4

2

39

D5

3

38

D6

4

37

D7

5

36

re3

6

35

FPhj*

7

34

Phtf

8

33

D3

9

32

D2

10

ANTIC

31

D1

11

30

D0

12

29

Ph2

13

28

A4

14

27

A5

15

26

A6

16

25

A7

17

24

A8

IS

23

A9

19

22

All

20

21

VDD

Figure 1-4. ANTIC Pin Assignments

Data Bus
Data Bus
Data Bus
Data Bus
Reset

Fast Phase 0 Clock
Phase 0 Clock
Data Bus
Data Bus
Data Bus
Data Bus
Phase 2 Clock
Address Bus
Address Bus
Address Bus
Address Bus
Address Bus
Address Bus
Address Bus
5V Power

ATARI Home Computer

1-9

Color Television Interface Adaptor

The Color Television Interface Adaptor (CTIA) chip retrieves graphics data from
memory via the ANTIC DMA process. This data is routed to the CTIA graphics
registers. Figure 1-5 illustrates the pin assignments for the CTIA and CTIA.

Address Bus

A1

Address Bus

A0

Ground

VSS

Data Bus

D3

Data Bus

D2

Data Bus

Dl

Data Bus

Dtf

Trigger 0

r

Tfi

Trigger 1

T1

Trigger 2

T2

Trigger 3

T3

Console Sw 0

sjfr

Console Sw 1

Si

Console SW 2

S2

Console SW 3

S3

PAL Color Delay

PAL

Color Delay

DEL

Alphanum. Data 0

AN0

Alphanum. Data 1

AN1

Alphanum. Data 2

AN2

1

2

3

4

5

6

7

8

9

10
11
12

13

14

15

16
17
IS

19

20

CTIA

40

39

38

37

36

35

34

33

321

31

30

29

28

27

26

25

24

23

22

21

A2

Address Bus

A3

Address Bus

A4

Address Bus

D4

Data Bus

D5

Data Bus

D6

Data Bus

D7

Data Bus

R/W

Read/Write

CSX

Chip Select 1

CS2

Chip Select 2

PH2

Phase 2 Input

FPHO

Clock Out

OSC

Oscillator Input

VDD

Power

HALT

HALT

CSYNC

Output Sync

LUM 2

Luminance 2 Output

LUM 1

Luminance 1 Output

LUM 2

Luminance 0 Output

COL

Color

Figure 1-5. CTIA/GTIA Pin Assignments

Graphics Television Interface Adaptor

The Graphic Television Interface Adaptor (GTIA) is an extended capabilities version of
the CTIA, having additional high-resolution modes.

I/O Decoder

J/Q Decoder integrated circuit (Z101) is a one-eight decoder demultiplexer. The
I/O Decoder is the same in the 400 and 800, but is labeled Z101 in the 800 Console and
Z105 in the 400 Console.

Composite Video

800 Mot herboards route the Composite video signals (COMP CHROMA,
COMP LUM, MOD, and COMP VIDEO) to the Power Supply to build the RF video
output.

ATARI Home Computers

1-10

Motherboard Console - 400

The 400 Console Motherboard contains the Pot Keyboard (POKEY) (A101) chip , the
Peripheral Interface Adaptor chip (PIA) (A102), the ROM Personality chips (A103 thru
A105), the Keyboard Key-In/Key-Out analog multiplexers, the Memory Map Decoder
(Z103), the controller jacks (3101 thru 3104), the CPU connector jack (3110), the
Keyboard connector jack, RAM connectors and Cartridge connectors.

Pot Keyboard Integrated Circuit

The Pot Keyboard Integrated Circuit (POKEY) provides the interface between the
Keyboard, the Serial I/O ports, and the microprocessor. It also contains four semi¬
independent audio channels, each with its own frequency, noise, and volume control.
Figure 1-6 shows the pin assignments of the POKEY.

Ground

YSS

Data Bus

D3

Data Bus

D4

Data Bus

D5

Data Bus

D6

Data Bus

D7

Phase 2 Clock

02

Pot Scan

P6

Pot Scan

P7

Pot Scan

P4

Pot Scan

P5

Pot Scan

P2

Pot Scan

P3

Pot Scan

P0

Pot Scan

PI

Keyboard Scan

KR2

5 V Power

VDD

Keyboard Scan

K5

Keyboard Scan

K4

Keyboard Scan

K3

1

2

•

40

39

3

38

4

37

5

36

6

35

7

34

8

33

9

32

10

POKEY

31

11

30

12

29

13

28

14

27

15

26

16

25

17

24

18

23

19

22

20

21

D2 Data Bus

D1 Data Bus

DO Data Bus

AUDIO Audio Out

A0 Address Bus

A1 Address Bus

A2 Address Bus

A3 Address Bus

R/W Read/Write Control
CS1 Chip Select

CSO Chip Select

IRQ Interrupt Request

SOD Serial Output Data

OCLK Serial Output Clock

BCLK Bidirectional Clock

KR1 Keyboard Scan

SID Serial Input Data

K0 Keyboard Scan

K1 Keyboard Scan

K2 Keyboard Scan

Figure 1-6. POKEY Pin Assignments

Peripheral Interface Adaptor

The Peripheral Interface Adaptor (PIA) (6520) has two 8-bit programmable I/O ports
and two control bits for each port, for a total of ten lines per port. Figure 1-7 shows
the pin assignments of the PIA.

ATARI Home Computers

1-11

vss-

PA*

PA1

PA2

PA3

PA#

PA3

PA4

PA7

P^*

PB1

PB2

PB3

PB#

PB3

PB4

PB7

CBl«*

CB2 ■

VCC-

1

-

*6

2

39

3

38

%

37

3

34

4

33

7

3#

S

33

9

32

10

MC54320

31

11

30

12

29

13

28

1#

27

13

24

14

23

17

2%

IS

23

13

22

20

21

y

CA1

CA2

fRQA

IRQB

RSI

RSI

&ESET

DO

D1

D2

D3

D#

D3

D6

07

• ENABLE

• CS1

- C52

• C

► R/W

Figure 1-7. PIA Pin Assignments

Key-In Key-Out Integrated Circuits

These two 4051 (Z101 and Z102) integrated circuits are used to scan the Keyboard for
input data on the 400 and 800 Computer Consoles. The 4051 integrated circuits are
analog multiplexers controlled by the input lines A, B, C and X.

Memory Map Decoder

The Memory Map Decoder integrated circuit (Z103) on the 400/800 Motherboard is a
one-of-ten decoder. Four input lines (pins 12, 13, and 14, and 15) determine which
output line is selected. The 400/800 Computer Console uses only three of the input
lines (pins 13, 14, and 15 and pin 12 being grounded) for a total of eight selected output
lines (SO -S7). Refer to Table 1-1 for the line selected for each input combination.

ATARI Home Computers

1-12

Table 1-1

Memory Map Selected Lines

Signal -

Pin -

Grd

12

A15

13

A14

14

A13

15

Active

Line

Device

L

L

L

L

1-SO

8K RAM BLOCK

L

L

L

H

2-SI

8K RAM BLOCK

L

L

H

L

3-S2

8K RAM BLOCK

L

L

H

H

4-S3

8K RAM BLOCK

L

H

L

L

5-S4

8K-RAM/CARTRIDGE L,R

L

H

L

H

6 - S5

8K RAM/CARTRIDGE L

L

H

H

L

7 - S6

2K ROM

L

H

H

L

7 - S6

I/O DECODER (Z105)

L

H

H

H

9 - S 7

4K ROMs (2-' , E'* <Sc "A")

I/O Decoder

2?! K? n eC °? Cr . mtegr 5 ted ci f cuit (Z105) 13 a one-of-eight decoder/demultiplexer.
POKFvi eCOd ^i S ifi ect the different output devices, such as PIA chip,

2 E ^WT 9 M d , h o f chl P‘ ? nl y four of the Possible output selections are

u ed. (See Table 1-2.) The I/O Decoder is enabled by inputs on pins 4, 5, and 6: pin *4

input coming from the Memory Map Decoder (S6), pin 5 input coming from the Address
Bus and Pin 6 input coming from the Chip Select (CS) line. The Binary Decode is
provided by the Address Bus (A08, A09 and A10).

ATARI Home Computers

1-13

Table 1-2

I/O Decoder Select Line

Enable

A12 All S6

Pin 6 6 4

Binary Decode

A10 A59

3 2

A8

1

Active

Pin

Device

Selected

H

L

L

L

L

L

YO- 15

CTIA

H

L

L

L

L

H

-14

Not used

H

L

L

L

H

L

Y2 -13

POKEY

H

L

L

L

H

H

Y3 -12

PIA

H

L

L

H

L

L

-11

Not Used

H

L

L

H

L

H

Y5 -10

External Select

-9

Not Used

■ 7

Not Used

Motherboard Console - 800

Read descriptions provided in Motherboard Console - 400, for items similar in both the
400 and 800 Console Motherboards. The following paragraphs describe those items
unique to the 800 Console Motherboard.

The 800 Console Motherboard contains the POKEY chip (A101), the PIA chip (A102),
the Keyboard Key-In/Key-Out analog multiplexers (Z103 and Z104), the I/O Decoder
(Z101), Bi-directional Data Buffers (Z105 and Z106), the controller jacks (3101 thru
3104), the Keyboard connector jack (3106), the left and right Program Cartridge jacks
(3108 and 3109), the CPU connector jack (3101), the ROM Personality connector jack
(3107), and the RAM Memory connector jacks (3102, 3103, and 3104). See Figures 1-11
and 1-12.

Bi-directional Data Buffer

The Bi-directional Data Buffers (Z105 and Z106) are 74LS243 quad transceivers,
commonly referred to as tri-level buffers. Tri-level refers to the three levels that can
occur in the device; the first level pin 1 going high and pin 13 staying low, allows data
to flow through the data buffer in the direction of the CPU; the second level, pin 13
going high and pin 1 staying low, allows data to flow through the data buffer in the
direction of the POKEY chip, the PIA chip and the Personality PCB; the third level,
with pin 1 and pin 13 both staying low, creates a high impedance condition in the data
buffers and allows other devices to transmit data on the Data Bus lines. This high
impedance state also isolates the CPU and the RAM PCB from noise generated from a
device using the Data Bus lines.

ATARI Home Computers

1-14

ROM Personality Board

The ROM Personality printed circuit board plugs into connector Jack J107 and
occupies memory locations DSOO thru FFFF. The Personality board contains the
operating system on three ROM chips, two 4K chips and one 2K chip (see Figures 1-13
pd 1-14). The two 4K ROM chips (A401 and A403) contain the I/O subsystem,
interrupt processing, initialization Power-Up and Reset. The 2K ROM chip (A402)
contains the floating point arithmetic package.

• I/Q~ Subsystem

The I/O subsystem contained in the ROM Operating System provides a
high-level interface between the user programs and the Console and
peripheral hardware. All peripheral devices capable of dealing with
character data have symbolic names (such as K, D, P, E) and may be
accessed using a Centrai I/O (CIO) routine.

• Interrupt Processine

All hardware interrupts are handled by the interrupt subsystem in the
Operating System. Vectored addresses contained in RAM memory point to
subroutines in ROM to handle each type of interrupt.

• Initialization

There are two levels of initialization provided by the system, Power-Up
Reset. Power-Up initialization is performed each time the system
power is turned on, and Reset initialization is performed each time the
Reset key is pressed.

Whenever the system power is turned on, the Operating System examines
and notes the configuration of the unit. The Operating System performs
the following actions at Power-Up:

Determines the highest available RAM address

Clears all RAM to zeroes

- Establishes all RAM interrupt vectors
Initializes the ROM Cartridges

Sets-up the video screen (24 x 40 text mode)

- Boots the cassette if desired

Checks ROM Cartridge for disk boot instructions
Boots the disk if desired and a disk drive is attached
Transfers control to the ROM cartridge, and booted program

ATARI Home Computers

1-15

Whenever the Reset key is pressed, the Operating System performs some, but not
all, of the functions performed at Power-Up. The Operating System performs
the following actions after the Reset key is pressed:

Clears the Operating System portion of RAM memory

- Re-establishes all RAM interrupt vectors

- Formats the Handler Address table
Initializes the ROM Cartridges

Sets-Up the video screen for 24 x 40 text mode

Transfers control to the ROM Cartridge and booted program

The remaining 2K of Operating System ROM is a floating point program which is
not used by the other parts of the Operating System itself, but is available to
non-resident programs such as BASIC, Calculator, PASCAL, etc. The following
routines are among those found in the ROM program:

ASCII to floating point and floating point to ASCII conversion

Integer to floating point and floating point to integer conversion

- Floating point log, exponent, and ploynomial evaluation

- Floating point number clear, load, store and move

POWER SUPPLY

The 400 and 800 Power Supply have identical circuitry, with a few exceptions (See
Figures 1-9 and 1-11). The Console Power Supplies receive 9Vac (3204 and 3206, 400
and 800 respectively) from the external power adaptor (transformer) provides +5Vdc,
and +12Vdc, and -5Vdc for the Console. Both the 400 and 800 Power Supplies have two
power ON/OFF switches, S202 and S203 for the 400 Console, and S201 and S202 for the
800 Console. S202 and S201, respectively, are Power Interlock switches.

The RF signal is generated in both the 400 and 800 Power Supplies from the MOD
signal received from the motherboard. It is routed through the A203 RF Module to
develop the RF output through 3203.

A peripheral connector jack, 3202 for the 400 Console and 3204 for the 800 Console,
provides the serial data-in/data-out port for the system. Devices are "daisy chained"
together from this output port. Each peripheral device is identified by a unique
address, enabling all devices to reside on one output port.

Also contained on the 800 Power Supply board is the Monitor connector jack (3205).
Present at 3205 are the composite video signals to drive a video monitor. The 800
Power Supply board also contains switches S204 thru S207. These switches are the
System Reset, Option, Select, and Start, respectively.

ATARI Home Computers

1-16

ROM CARTRIDGE

The .£ tan R0M Program Cartridge contains two ROM chips designed to provide a
specific program application (See Figure 1-16). The 6502 microprocessor reads the
mrcc Tiatl0n contained Wlthm the R0 ® Chips by addressing memory locations S000 thru
BFFF Hex. When the ROM Program Cartridges are inserted in the motherboard, they
disable the RAM address locations 8000 thru BFFF, in 8K increments. The left ROM
Cartridge overlays memory locations A000 to BFFF, and the right ROM Cartridee
overlays locations 8000 to 9FFF. 6 &

ACCESSORIES

AC Power Adaptor

The AC Power Adaptor plugs into a standard wall outlet to provide the 9Vac used by

the Consoles. The other end of the power adaptor plugs into the power jack on either
Console.

TV Switch Box

The TV Switch Box allows the Console to be connected to the 300 ohm RF antenna or
75 ohm cable inputs on a typical televison set.

'BASIC* Program Cartridge

Jnntl^c S !f AT > AD a r n l5?T^ r T idse ( P rovided) is a standard feature for both Consoles and
contains the ATARI BASIC Interpreter.

ATARI Home Computers

1-17

came switches

ATARI Home Computers

1-18

TO/FM POWER SUPPLY

s

Figure 1-9. 400 Power Supply

ATARI Home Computers

1-19

POWER SUPPLY BOARD
ATARI *00

ATARI Home Computers

Figure 1-10. 800 Motherboard Flow Diagram

1-20

ATARI Home Computers

1-21

COMPOSITE VIDEO

Figure 1-12. 800 Personality Board
ATARI Home Computer 1-22

PERSONALITY HOARD
ATARI 800

ADDRESS BUS L ADDRESS BUS

DATA BUS (DM

ATARI Home Computers

• 1-24

SK DYNAMIC RAM
ATARI

DATA OUT

ATARI Home Computers

1-25

16K DYNAMIC RAM
ATARI

<

qT<0

j=>C* £

2H

«- Z

<IUJ D

a a < uu

5 H
o u -

o o UJ
-J cd

CO

D

cQ

CO

CO

UJ

oL

a

a

<

2

tU

>

►-*

oi

a

au

A

1 _

CTHVOffH3H.LOW Ol

Figure 1-16. Game Cartridge Flow Diagram

ATARI Home Computers

1-26

GAME CARTRIDGE BOARD

ATARI HOME COMPUTER SYSTEM BLOCK DIAGRAM

ATARI Home Computers

1-27

20MA CURRENT LOOP PORT

SECTION 2

SILKSCREEN AND SCHEMATICS

/Inin P a S es contain representative siikscreens and schematics for the ATARI

400/800 Computer Consoles. Minor variations in design may be encountered depending
upon the production date of the Console. These drawings provide all details required *
for an in-depth understanding of both the 400 and 800 Consoles.

ATARI Home Computer

2-1

THIS FAG1 INTENTIONALLY LEFT BLANK

ATARI Home Computer

2-2

Figure 2-1. 400 Motherboard Silkscreen

ATARI Home Computer

2-3

a
01 .

< 3

O |f S]

CD §*«*

400 MOTHER BOARD

TO POWER SUPPLY

Figure 2-3. 400 Power Supply Silkscreen

ATARI Home Computer

2-6

THIS PAGE INTENTIONALLY LEFT BLANK

ATARI Home Computer

2-8

Figure 2-5. 800 Motherboard Silkscreen

ATARI Home Computer

2-9

800 MOTHER BOARD

Page 1 of 2

ATARI Home Computer

2-10

ATARI Home Computer

2-13

C404

zoto

Nl

C\J

O

<

Figure 2-9. 800 Personality Board Silkscreen

ATARI Home Computer

2-14

PERSONALITY BOARD
ATARI 800

ATARI Home Computer

2-15

74L900

Figure 2-11. CPU Board Silkscreen
ATARI Home Computer 2-16

A302 A303 HJ07

C 307 <

CPU BOARD

*8

CD

m

o

Figure 2-13. 8K RAM Board Silkscreen

ATARI Home Computer

2-18

8K RAM

ATARI Home Computer

2-19

l/W CATf

L OSZ

60SZ

219 Z

Figure 2-15. 16K RAM Board Silkscreen

ATARI Home Computer

2-20

Z502 Z504

I6K RAM

Figure 2-16. 16K RAM Board Schematic

ATARI Home Computer

2-21

SECTION 3

TROUBLESHOOTING AND TESTING

OVERVIEW

This section describes the procedures to maintain, troubleshoot, and test the ATARI
400/800 Computer Consoles. The section is divided into two major categories:

L TESTS

2. TROUBLESHOOTING

TESTS

The following discussions pertain to the troubleshooting procedures required
checkout the ATARI 400/800 Home Computer Consoles.

to

Equipment Needed

You require six basic pieces of equipment in order to analyze
ATARI 400/800 Home Computer Console. These items include:

• 15MHz oscilloscope

• Stand Alone Test Cartridge (SALT II)

• Peripheral Port Test Connector

• Hand Controller Jack Test Connector

• Television Set (properly adjusted)

• Small Tool Kit

the failures of the

ATARI Home Computer

3-1

Testing With And Without The SALT II Cartridge

All tests are reviewed in this section. Procedures for the use of the tests are det aile d
in Section 5, 400 Diagnostic Flowchart, and Section 7, 800 Diagnostic Flowchart.

OVERVIEW OF TESTS

A variety of test routines assist you in identifying probable sources of problems within
the computer console.

Power-Up Test

This test prepares the Console for the remainder of the tests. Should the Console fail
this test, no other test results can be considered valid.

• Format: Connect the power adaptor to the Computer and the Computer to
the television set. Make sure there is not a cartridge in the console —turn
the POWER switch ON. The words ATARI COMPUTER - MEMO PAD
should appear on the screen in the upper left corner.

Keyboard Test

This test verifies that all keys of the keyboard are properly functioning. This test also
verifies that the POKEY chip's keyboard functions are operating properly. If one key
fails, then the problem is likely the keyboard. If more than one key fails, you must
perform further tests. (These tests are discussed later in this section.)

• Format: Depress each key of the keyboard. As you press each key, watch
scree n to verify if the computer is echoing the key. Be certain to use
the CTRL key with other keys. This checks special graphics functions not
tested elsewhere (See Figure 3-1).

RAM and ROM Test

This test verifies that the CPU, RAM, and ROM chips are all properly functioning.

• Format: Due to the possible complexity of this test, it has been broken
into four subsections.

1. Turn the POWER off, insert the SALT II cartridge (for the 800, use
the left cartridge slot), and turn the POWER on. The SALT Header
should appear on the television screen (See Figure 3-2). This verifies
that the CPU, Operating System (OS) ROMS, and the lower RAM are
functioning.

ATARI Home Computer

3-2

DO THIS

SEE THIS

Figure 3-1. Special Graphics Test

ATARI Home Computer

3-3

□□□□□EE

ATARI 400/800
STAND ALONE
SYSTEM TEST

REV 2 04 (C) 1981

_(T_Y_PE__ ?___FOR_HELPJ_

RAM:40K TIA NTSC
ROM: MATH ~NTiA : NTS A

Figure 3-2. SALT Header

2. If a green/yellow colored screen is returned, this indicates a probable
OS ROM malfunction. Swap-out the ROM set with a known good set
(make certain to test after each ROM is replaced), this allows you to
pinpoint the defective ROM.

3. If the words, SYSTEM FAILURE appear on the television screen, this
indicates that the lower RAM is not functioning. When this happens
and a 400 Computer is under test, turn the POWER off, swap-out the
RAM board with a known good one and turn the Power on. If the
SALT Header is returned to the screen, this indicates a probable
malfunction in the RAM board which was removed. Refer to the
DIAGNOSTIC FLOWCHARTS, Section 5 and 7 for troubleshooting
procedures.

If the 800 Computer is under test, turn the POWER off and swap-out
the front RAM Card with a know good one. Place the suspected
defective RAM CARD into the number 2 RAM slot (the third slot
behind the OS), and turn the POWER back on. This lets the SALT II
cartridge troubleshoot the suspected RAM CARD later in the
DIAGNOSTIC FLOWCHARTS.

^ RAM and ROM boards have been swapped and the condition
continues to persist, swap the CPU board with a known good board to
isolate the problems.

ATARI Home Computer

3-4

* * * NOTE * * *

Once you have isolated the problem to either the RAM, ROM, or
CPU boards, clean the board edge connectors and retest the boards.

The SALT II cartridge takes you through the next phase of tests. Use the SALT II
cartridge to perform the following tests.

SALT II Menu

Figure 3-3 illustrates the SALT II menu of tests. The highlighted character in Figure
is red on the screen and is the command letter for each test.

ANY

COLOR^ARS

nl RT TEST

Bum

UpF^SoM

2PRODUCTION TEST

HELP

IBOOT B
IC>t §£LAY

iTiii ST
LIGHT PEN
7HELP

Figure 3-3. SALT II Menu

ATARI Home Computer

3-5

Color Bar Test

This test verifies and allows for adjustment to the color circuitry. With SALT II
properly in place, enter the command letter C and press RETURN. Figure 3-4 is a
black and white representation of what your television display screen should look like.

Figure 3-4. Color Bar Test Screen

A 15-color rainbow scale is displayed above the reference bar with a single color bar
below. The color bars directly above and below the reference bar should be the same
color (golden rod). If not, proper adjustment of R309 makes the color bars above and
below the reference bar identical thus adjusting the color frequency of the console to
the proper setting.

ATARI Home Computer

3-6

Proper operation of the unit is indicated by you being able to make this adjustment and
by consistent color within the entire span of each bar on the screen. Minor glitches on
the edges of the color bars are acceptable. Leave this test on for at least 60 seconds

in order to catch any intermittent problems, such as a bar momentarily changing
colors or blanking out. 1 66

Any Video Test

This test verifies the console’s ability to generate a video (TV) display. This test also
checks for pattern sensitivity of the ANTIC chip.

By entering the command letter A and pressing RETURN, this test is activated.

Figure 3-5 illustrates the screen display for the Any Video Test. NOTE; Figure 3-5 is
a black and white representation of a colored screen.

The screen should have a black background with eight vertical bars. Half of the
vertical bars should be narrow, and the other half, much wider. A horizontal bar
should appear across the top of the screen. From the left to right, the shade of color
on the horizontal bar should change. On the right of the bar, two Vs should be
displayed, right side up} one in normal video and the other in inverse video*

Figure 3-5. Any Video Test Screen

ATARI Home Computer

3-7

Gray Bar Test

This test verifies that the CTIA (GTIA) is generating the three LUM lines.

By pressing the command letter G and then RETURN, this test activates.

Figure 3-6 illustrates the screen display of the Gray Bar Test. The screen is divided
into eight equal sized horizontal bars. The bar at the top of the screen should be black
and subsequent bars should progress to white at bar eight. The bars should lighten in
even shades. The screen should be steady and unchanging. These lines may have minor
glitches at their edges. A thin white line should always appear just over the top
(black) bar. No color should appear anywhere on the screen. The areas above the top
(black) bar and below the bottom (white) bar are of no importance to this test. This
test should be left on for at least 60 seconds to ensure that there is no "flashing" of
color or shifting of the gray bars.

Figure 3-6. Gray Bar Test Screen

ATARI Home Computer

3-8

Keyboard Test

keyboard Verifles the Console's ability to accurately accept operator input from the

By pressing the command letter K and RETURN, this test is activated. You are to
press each of the keys EXCEPT, the SPACE BAR, CNTL and both SHIFT keys. Each
letter pressed is returned to the display screen. Once this portion of the test is
completed, hold down the CNTL key and press the letter A. The letters CTRL are
SS? C . d t0 *. the j Cree f 1 * Now > hold down the left SH IFT key and press A. The word
th^oM r «SS- ed t0 screen - B y h u oldin g down the right SHIFT key and pressing A,
InH 7h d returned t0 the display screen. Finally, press the SPACE BAR

and then, RETURN. The words KEYBOARD PASS or KEYBOARD FAIL appear on the

th^ k ! Y f^f- d t f St * If the SALT n cartridge detects any key failures

during the test, the defective keys appear on the screen in the color red.

Switch Test

OPTTnw P/°E! r c2^ ratl ^ n of the four Cons ole Switches (START, SELECT,

RETURN ^h d ? Y ^ T - EM ^ E5E ?‘ _ B y Pressing the command letter S and pressing
STADT^^^ntB 6 ^ 15 v C ^ ed ’ Press the console switches in the following order: 1)

SIS 3) P ™ 5 and 4) SYSTEM Upon pressing’SYSTEM

KtocT, either PASS or FAIL is returned to the screen.

Tone Test

te f veri f. ies th . e abmt y of the POKEY to generate four sound registers through its

(Zu2?t£n) e - raU °J? Cir , CUltS : Press the command letter T and RETURN. A prompt
^ is returned to the screen asking you which register you want to test. You

Sen p P re e i S I^TUR y Nr tH ** nUmber ° f the re S ister y° u want to test (1, 2, 3, or 4) and

T^f generates eight tones in descending order. The first three tones are very high

^ d 7 a ^n b rn mau 1 dlble to v some P e °P ie - Each tone begins at maximum volume and fadls

MaSe ceTtaTn Z tZV, l . f ° U must ® nter the command letter before each register test.
fviaKe certain to test all four sound registers.

NOTE: The television volume control may have to be turned up in order for you
to hear the first three tones.

ATARI Home Computer

3-9

Display Options

This function, which is not a test, displays a diagnostic matrix when used in
conjunction with either the RAM TEST or the PORT TEST. It allows you to identify
which ROM chip has failed when used with the VERIFY ROM TEST.

By pressing command letter D and RETURN you access this function. The screen
returns the prompt to enter a test format. To use the PASS/FAIL indicator, enter the
command letter P and press RETURN. To display the ERROR TABLE, enter the
command letter E and press RETURN. For the following PORT, VERIFY ROM, and
RAM TESTs, press the command letter E and RETURN. The screen prompts you to
enter the command letter S for a single test, or C for continuous testing.

You are now ready for the three tests. To terminate any of the following three tests,
press the SPACE BAR. NOTE; The RAM test completes its current test before
stopping.

Port Test

This test verifies the ability of the computer system to communicate through the
controller jacks and the peripheral I/O port.

The command letter P and RETURN activates this test. Make certain that the
Peripheral Jumpers are in place, and press RETURN again. Figure 3-7 illustrates the
Port Test Matrix Display. This figure is a black and white representation of a color
television screen. The zeros should be a blue tint.

ERROR

COUNTER

TEST

COUNTER

ATARI Home Computer

3-10

The four digit number in the lower-right corner of the display screen shows the number
of tests completed. In addition, the four digit number above it in red is an error
counter which indicates the number of times the test has failed.

If a failure occurs, a Red 1 is displayed in the matrix, this shows you the location of

2?,c« rr °/^ C r d , ition * T* b . Ie 3-1 ’ Port Test Legend should be used to determine the
cause of the failure condition. (Please note, a blinking 1 at location A 5 does not
indicate a failure,)

A passrng condition for all test is indicated by a 0 in that location (i.e., CO or D4). If
the failed test passes on the next pass, the 1 is replaced by a 0. The error counter in
the lower-right corner of the screen increments by one for each error .

Verify ROM Test

This test checks the Console's ROMs by performing checksum tests on them. By

entering the command letter V and pressing RETURN you activate this test. The

screen displays a checksum for each ROM and the value returned by the MATH PACK

together with a PASS or FAIL indicator for each. Upon completion of the test the

R?M and either PASS or FAIL for the S tcTt° ££’»«

1'I uch ,a 0M “ Iallln 8- lf y° u suspect a ROM is intermittently
tailing, run this test for 15 or 20 minutes*

RAM Test

This automatically uses six different tests to verify the operation of the RAM boards

r E e n ^nedVt^ m i nd R ^ PrCSS RETURN to this test. A prompt is

five) TvDe the ™mhTr ^ king how 8K bIocks of memory to check (maximum of

that 1 Ia£al™h"J kr am™*™? 1 " 7 5 “? the unit and P ress RETURN. (Remember

tnat, l equals each 8K RAM card and 2 equals each 16K RAM.)

Mt.r.T P „ U nTr, d tT layS am ° Unt 0i RAM is ,es,in 8- “ amount is not what you
' “red, one of two conditions may exist: 1) the unit does not contain the amount of

memory you thought it did; or, 2) the unit has defective RAM card(s).

mimhpr 3 in Elustratesa defective RAM test system response screen. The four digit
comnfJJP wblte 3t ^e bottom right of the screen indicates the number of tests
failures d ‘ A d ^ dlglt number direct ^ above this is used to count the number of

ATARI Home Computer

3-11

(f-ff
3P yd

/<T fU-yO/4^

of

•2\ C f /~f~( /<S"£-^

ys l-l l fy/SrJL;

As was the case with the PORT Test, failures appear as Red Is in this display. If the
pattern is in a state of constant change, one of the RAM boards probably has a set of
defective 74LS158 chips. If you replace the chips make certain that the new chips
have the same manufacturer and the same date code. This ensures compatibility. To
determine which board(s) is(are) defective, perform the following three steps:

1) Turn off the power.

2) Remove one of the boards.

3) Start the test from Display Options, page 3-10.

If the pattern is stable, look at line B, Columns 4 thru 7 to determine which board is
defective. (See Table 3-2).

ERROR

COUNTER

TEST

COUNTER

ATARI Home Computer

3-13

Table 3-2

Defective RAM Boards

Defect

Indicator

Description

B4

1st 8K Block

B5; or

B4 and B5

2nd 8K Block

B6j or

B4 and B6

3rd 8K Block

B5 and B6;

or

B4, B5 and

B6

4th 8K Block

B7; or

B4 and B7

5th 8K Block

Compare rows D and E, if there is a difference between any one column use Table 3-3
to identify specific defective chips. If more than one column is different replace the
74LS244 chip and retest.

ATARI Home Computer

3-14

Table 3-3

Defective RAM Identifier

Difference

Column

Description

8K

16K

DO

Z512

Z512

D1

Z511

Z511

D2

Z510

Z510

D3

Z508

Z509

D4

Z509

Z508

D5

Z507

Z507

D6

Z505

Z506

D 7

Z506

Z505

M Test

This^test verifies the proper operation of the Video Buffer Chip (400-All 1 and 800-

InJrf th rm n t A h S^ teSt ’ off * he ConsoIe POWER, remove the SALT II cartridge and
SSies: C BASIC Cartridge * Turn the POWER on Perform the following 2 three

ATARI Home Computer

3-15

1) Type: NEW and press RETURN.

2) Type: 10?"M"; :GOTO 10 and press RETURN.

3) Type: RUN and press RETURN.

The system starts printing Ms, character after character, line after line. If any are
blurred and/or run together, the Video Buffer Chip or another of the discrete
components in the video summing circuitry on the mainboard is probably defective.

To stop this test, press BREAK or SYSTEM RESET.

STAR RAIDER™ Test

If the Console has effectively passed all previous tests and performs this game without
any visible problems, it is almost certainly operating properly.

Turn POWER off, remove the BASIC cartridge, insert the STAR RAIDER™ cartridge,
and turn the POWER on. Now, go through the game's various screens and functions
(play the game).

Shake Test

Grasp the unit firmly with both hands and shake it vigorously for approximately 10 to
20 seconds. DO NOT HIT or STRIKE the unit against the bench or other hard object
T th ?, U «L h ^ V o* g y0ur fin S ers between the unit and the surface being struck. Perform
the MEMO PAD test to make certain that none of the connections, boards, and/or
components have become unseated, and that the unit is properly operational.

Burnin

After the unit has successfully passed all the previous procedures and is operating
correctly, it is ready for burnin °

Burnin consists of operating the system continuously for a long period of time
(recommended 8 hours). Use one of the following three methods.

1) Insert the SALT II cartridge and run it with continuous RAM or PORT test.

2) Insert Star Raider or another game cartridge and run it.

3) Perform the 400/800 Console Test (810 Disk Drive required).

ATARI Home Computer

3-16

At the end of the BURN-IN period, check the unit again for any malfunctions, using
SALT II Test checks. Once the unit has passed all the final checkout procedures, it is
ready to be returned to the customer.

DESCRIPTION OF THE OTHER FUNCTIONS FOLLOWS;

Production Test

Command letter "Z". This function allows you to run through the series of test semi-
automatically by pressing the space bar. It will ask you the serial number of the unit
and print it out on a printer with the word PASS or FAIL.

Boot B

This function is not used at this time.
Examine

Command letter "E". This allows you to test a specified RAM location (address).

Adjust

Command letter "J". This is used to debug audio and serial port control lines (Motor
Go & Command) on the system console. A fixed frequency audio signal is produced
while PIA ports are exercised.

SUMMARY

This section has taken you step-by-step through all the tests and general
troubleshooting steps required for evaluation of a suspect defective 400/800 console.
Now read through the section, DISASSEMBLY and ASSEMBLY, before going on to
Section 5, Diagnostic Flowcharts, and Section 7, 800 Diagnostic Flowchart.

ATARI Home Computer

3-17

SECTION 4

DISSASSEMBLLY/ASSEMBLY MAINTENANCE

ATARI 400 HOME COMPUTER CONSOLE - DISASSEMBLY

The following describes the procedures required to disassemble the 400 Computer
Console. Read the following NOTES first, then proceed.

* * * NOTE * * *

!• Be very careful about mixing screws. Plastic and aluminum
parts can be easily stripped or damaged by puncture if the
wrong size screw is used.

2. Excessive torque on screws can strip the plastic and aluminum
parts.

o P l asti c - 6-inch pounds torque maximum,
o Aluminum - 10-inch pounds torque maximum.

3. Protect the plastic surfaces of the console by working on a
soft surface (a grounding pad works very well) when the
Console is turned over, bottom up.

4. Use ALL static control precautions when handling any printed
circuit board.

KEYBOARD AND POWER SUPPLY ACCESS

To remove the top cover, perform the steps in the exact order given.

• Turn the unit side down.

• Remove four screws from the bottom cover (See Figure 4-1).

ATARI Home Computer

4-1

atari Home Computer

4-3

KCYBOAftO

V

Figure 4-3. ATARI 400 Console, Keyboard Removal

POWER SUPPLY REMOVAL

J,° r 5! T10ve the power supply, perform the following steps in the exact order given.
Use Figure 4-4 as a reference for the following four steps.

• Disconnect RF cable from power supply.

• Remove two screws from power supply.

• Gently pull power supply away from casting 1/4 inch and lift out the
interlock switch plunger.

• Lift the power supply straight-up off the motherboard connector pins.

ATARI Home Computer

4-4

INTERLOCK PLUNGER

Figure 4-4. ATARI 400 Console, Power Supply Removal

ATARI Home Computer

4-5

CPU, RAM. AND MOTHERBOARD ACCESS

To remove the module assembly, perform the steps in the exact order given. Use
Figure 4-5 as a reference for the following two steps.

• Disconnect and remove speaker assembly.

• Lift module assembly out of the bottom cover.

CPU AND RAM REMOVAL

To remove the CPU and RAM printed circuit boards, perform the steps in the exact
order given. Use Figure 4-5 as a reference for the following six steps.

• Close and latch the cartridge door.

• Set the module on its back.

• Remove the eight screws from the bottom shield and lift off the shield.

• Lift the motherboard assembly out of the aluminum casting.

• Carefully unplug the CPU and/or RAM boards.

• Unhook and remove the plastic cartridge guide.

ATARI Home Computer

4-6

ALUMINUM CASTING

CPU
BOARD

RAM

BOARD

CARTRIDGE

GUIDE

MOTHER BOARD

80TT0M SHIELD

SPEAKER

ASSEMBLY

Figure 4-5. ATARI 400 Console, Module Assembly

This concludes the disassembly of the 400 computer console.

ATARI Home Computer

4-7

ATARI 800 HOME COMPUTER CONSOLE - DISASSEMBLY

The following describes the procedures required to disassemble the ATARI 800 Home
Computer console. Read the NOTES on pages 4-1 thru 4- 3 first, and then proceed.

ACCESS TO RAM BOARDS AND ROM BOARD

To gain access to the RAM and ROM boards, perform the steps in the exact order
given.

Remove the cartridge door assembly. Use Figure 4-6 as a reference for the following
eight steps.

• Turn the system power switch to the OFF position.

• Open the cartridge door.

• Turn the cartridge door clamps towards the outside of the Console.

• Lift the cartridge door assembly 1/4 inch, pull it towards you, and lift it

off.

Remove the RAM and ROM modules.

• Lift out the RAM module(s).

• Lift out the ROM module.

• Lift out any cartridge(s).

• Turn cartridge door clamps to original position.

ATARI Home Computer

4-8

CARTRIDGE DOOR
ASSEMBLY

Figure 4-6. ATARI 800 Console, Cartridge Door Assembly Removal
ACCESS TO POWER SUPPLY AND KEYBOARD ASSEMBLY

To gain access to the power supply and keyboard assembly, perform the following steps
in the exact order given.

REMOVE TOP COVER

Use Figure 4-7 as reference for the following three steps.

• Turn unit upside down.

• Remove five screws from the bottom cover.

• Tilt the back of the bottom cover up and towards you to remove it.

ATARI Home Computer

4-9

BOTTOM COVER

Figure 4-7. ATARI 800 Console, Bottom Cover Removal

REMOVE THE PCB MODULE

Use Figure 4-8 as a reference for the following seven steps.

• Remove two screws from the aluminum casting flange.

• Remove the single screw from the power supply board (lower left corner).

• Disconnect speaker cable, remove speaker and set it aside.

• Turn the unit over.

• Carefully pull the back of the console top cover assembly to 90° separating

it from the PCB module. °

ATARI Home Computer

4-10

• Reach over the top cover and unplug the keyboard's ribbon cable.

• Set the top cover assembly aside.

Lift the power supply board straight up.

Remove plastic cartridge guide by
side of the motherboard.

unhooking the latches from the bottom

SPEAKER

harness

Figure 4-8. A1ARI 800 Console, Module Assembly Removal
REMOVE THE POWER SUPPLY

Use Figure 4-9 as a reference for the following five steps.

• Unplug the RF cable from the power supply board.

• Unplug the power supply harness.

• Remove three screws from power supply board.

ATARI Home Computer

4-11

POWER

RF CABLE SUPPLY

WIRE HARNESS

Figure 4-9. ATARI 800 Console, Power Supply Removal

ACCESS TO CPU PRINTED CIRCUIT BOARD

Use Figure 4-10 as reference for the following four steps.

• Turn the unit upside down.

• Remove the nine screws from the lower shield.

• Lift the motherboard and lower shield out of the aluminum casting

• Remove the CPU PCB.

ATARI Home Computer

4-12

ACCESS TO MOTHERBOARD

Use Figure 4-11 as reference for the following three steps.

• Carefully slide the tip of a screwdriver underneath the motherboard next
to the nylon clip. Gently raise the handle of the screwdriver, prying off
the nylon clip. Repeat this operation for the remaining three nylon clips.

* * * CAUTION * * *

Be careful not to bend any of the pins on the Motherboard
Connector.

Do NOT allow the tip of the screwdriver to damage traces.

ATARI Home Computer

4-13

• Lift the motherboard off the lower shield.

• Remove the plastic cartridge guide by unhooking the four latches from the
bottom side of the motherboard.

Figure 4-11. ATARI 800 Console, Motherboard Removal

KEYBOARD REMOVAL

Use Figure 4-12 as reference for the three steps, to remove the keyboard from its
case.

• Turn the top cover upside down.

• Remove four screws from the four corners of the keyboard.

• Lift the keyboard out of the top cover.

This concludes the disassembly of the Atari 800 Home Computer console.

ATARI Home Computer

4-14

T

KEYBOARD

Figure 4-12. ATARI 800 Console, Keyboard Removal

ATARI 400 HOME COMPUTER CONSOLE ASSSEMBLY

The following outlines the steps required to reassemble the Atari 400
console and it's related printed circuit boards.

Home Computer

MODULE ASSEMBLY REASSEMBLY

Refer to Figure 4-5 as reference for the following five steps.

• Snap the cartridge guide into the motherboard (it only goes in one way).

• Insert RAM and CPU printed circuit boards into the motherboard with the

^ mP D^n nt Sld ^ ° f the PCBs facin s awa y from you. Before reassembling
the PCBs, make certain that they have been cleaned and lubricated.
(Refer to pages 4-21 and 4-22 for instructions.)

• Set aluminum casting upside down, invert the motherboard and gently
lower it into the casting.

Atari Home Computer

4-15

* * * NOTE * * *

The CPU PCB must fit into the guides in the aluminum casting.

• Install lower shield and secure it with eight screws.

• Install the module assembly in the bottom cover.

KEYBOARD INSTALLATION

Refer to Figure 4-3 as a reference for the following three steps.

• Plug the speaker cable into the motherboard (no Polarity) and set the
speaker into the bottom cover.

• Plug the keyboard ribbon cable into the connector on the motherboard.

• Gently lower the keyboard over the Power-ON LED and guide posts on the
aluminum casting.

POWER SUPPLY INSTALLATION

Use Figure 4-4 as reference for the following five steps.

• Align the power supply over the motherboard connector pins and bottom
cover guide posts and gently press it down.

• Install the interlock switch plunger into the aluminum casting. Make
certain that the lower end of the plunger is positioned over the interlock
switch and the plunger shaft rides in its notch in the power supply heat
sink.

• Insert and tighten the two power supply mounting screws.

* * * CAUTION * * *

Be sure that the RF cable is not trapped under the module assembly.

Route the RF cable through its slot in the power supply board and plug it
into the power supply jack.

Insert and tighten the single keyboard mounting screw.

Atari Home Computer

4-16

TOP COVER INSTALLATION

• Open the cartridge door.

• Slide the top cover down over the open cartridge door and the power-ON
LED (Refer to Figure 4-2).

• Guide the top cover locator pins into the keyboard holes and snap the top
cover hood under the keyboard.

• Close the cartridge door and set the console on its face.

• Align the top and bottom covers and insert the four screws into the bottom
cover and tighten (Refer to Figure 4-1).

ATARI 300 HOME COMPUTER CONSOLE ASSEMBLY

The following outlines the steps required to reassemble the Atari 800 Home Computer
Console and its related printed circuit boards.

KEYBOARD INSTALLATION

Refer to Figure 4-12 as reference for the following two steps.

• Set the top cover upside down with the keyboard in it.

• Insert and tighten the four mounting screws.

* * * NOTE * * *

Check the spacebar and keys to make sure that they are not binding
before proceeding.

MOTHERBOARD INSTALLATION

Refer to Figure 4-11 as reference for the following two steps.

• Snap the plastic cartridge guide into the top side of the motherboard.

• With the motherboard right side up, snap on the four nylon clips of the
lower shield. Make certain all four clips are firmly seated.

Atari Home Computer

4-17

CPU PCB INSTALLATION

Refer to Figure 4-10 as reference for the following five steps.

• Plug in CPU PCB. Make certain the component side of the board faces
away from the plastic cartridge guide and is firmly seated.

• Turn the aluminum casting over.

• Turn the motherboard upside down and set the motherboard and lower
shield into the aluminum casting.

* * * CAUTION * * *

Make certain that the CPU PCB sets in its slot in the aluminum
casting.

• Insert and secure the nine screws in the lower shield.

• Set the console on its feet.

POWER SUPPLY INSTALLATION

Refer to Figure 4-9 as reference for the following six steps.

• Carefully align the power supply connector with the motherboard pins.

• Set the power supply down over the guide pins on the aluminum casting and
gently press down.

• Attach strip connector between power supply and motherboard.

• Insert and tighten the three screws of the power supply board.

• Recommend the power supply harness.

* * * CAUTION * * *

Plug the power supply harness cable from the motherboard to the
P 0 *® 1 supply pins with the orange or purple wire towards the
aluminum casting.

• Plug the RF cable, the short end, into the power supply jack.

Atari Home Computer

4-1S

MODULE ASSEMBLY INSTALLATION INTO TOP COVER

Refer to Figure 4-8 as reference for the following six steps.

• Set the top cover upside down.

• Invert the module assembly and lower it into the top cover. Turn the
cartridge door latches toward the inside in order to clear the top cover.

* * * CAUTION * * *

Make certain that the RF cable is not trapped between the power
supply board and the top cover standoff (upper left screw hole).

• Lift the motherboard one-inch out of the top cover and plug in the
keyboard harness.

• Insert and tighten two screws into the front holes of the aluminum casting

and into the top cover. °

• Set the speaker into its receptacle foam side down.

• Connect the speaker cable to the jack (no polarity).

bottom cover installation

Refer to Figure 4-7 as reference for the following four steps.

• Align the bottom cover with the four-hand-controller ports.

• Seat bottom cover firmly, all the way around. Make certain the RF cable
exists through its hole and is not trapped between the covers.

• Insert and tighten the five bottom cover screws.

• Set the console right side up.

Atari Home Computer

4-19

RAM AND ROM MODULE INSTALLATION

Refer to Figure 4-6 as reference for the following two steps.

• Insert the ROM Module in the slot closest to the keyboard.

• Insert a maximum of three RAM modules in the remaining slots.

CARTRIDGE DOOR ASSEMBLY

Refer to Figure 4-7 as reference for the following two steps.

• . Set the cartridge door assembly on the top cover and slide it to the rear of

the cover. This action engages the tab of the door into the aluminum
casting.

• Lock the cartridge door assembly down with the two clamps next to the
program cartridge slots.

PCB CONTACT CLEANING AND LUBRICATION

The following instructions explain the procedures required to properly clean and
lubricate the PCB contacts of the CPU, RAM and ROM boards once they have been
removed from the motherboard.

Tools Required

• ZEP Safety Solvent or Isopropyl Alcohol

• Dust-Free Cloth

• Acid Brush

• Board Cleaning Brush

• Libriplate (DS-ES Lubricant)

Procedures

Inspect the PCB contact for flux, dirt, foreign material, and deeply serated
contact fingers.

Moisten the dust-free cloth with solvent and clean the finger contacts.
Make sure both sides of the contacts are clean and free of residual
lubricant and contamination.

Atari Home Computer

4-20

* * * NOTE * * *

Avoid touching the contact after cleaning.

3. If corrosion or residue remain on the contacts it is necessary to clean the
contacts further using the board cleaning brush. Use the following
procedures.

• Moisten the board cleaning brush with solvent and firmly brush the
contacts. Four to six strokes is enough. Be careful and do not touch
any other part of the board.

• Perform step 2 again.

4. Dip the acid brush into the lubricant.

5. Apply an even coating of lubricant to the contact fingers on both sides of
the PCB. The coating of lubricant should be thick enough to protect the
contact fingers from corrosion. Do not spread the lubricant to areas other
than the contact fingers.

VISUAL INSPECTION

ortbuse 0 ^ 8 inStructions ex P lain specific areas to check on the Consoles for damage

1. Inspect the controller jacks and peripheral jacks for broken and/or bent
pins.

2. Check the RF cable for cracks in the insulation, bare, or pinched areas.

3. With the console power ON and MEMO PAD on the screen, open the
cartridge door to check the interlock switch. Using a small blade
screwdriver, press the plunger down. Release the plunger and see that it is

returns to its open position. In its open position the console is powered-
down.

4. Inspect the cartridge slot for foreign objects or damage.

5. Inspect the power jack for bent and/or damaged pins.

If any of the above damage is found, repair the defective area. Use the disassembly
and assembly instructions at the beginning of this section.

Atari Home Computer

4-21

SECTION 5

400 DIAGNOSTIC FLOWCHART

The Diagnostic Flowchart is intended to be easy to use and the primary aid when
troubleshooting the ATARI 400 Computer Console. Follow the prompts in the order
presented. When a question is asked, follow the line from that box which best applies
to the unit's situation. The flowchart leaves little to chance, it tells you when to
perform a specific test and when to replace components.

Swap Out Procedure

At many places in the diagnostic flowchart, a box tells you to "swap-out" a chip or a
^mber of chips in a particular order. The "swap-out" instruction means that you
should replace the indicated components (one at a time) with a known good component
of the same type. The 400 should then be tested with the new, known-good component
in place to see whether the "swap-out" solved the problem being checked. If the swap-
out did not fix the problem, the known-good component should be removed, and the
original component reinserted. In this way, you avoid needlessly replacing good
components. K 66

CAUTION:

Extreme care should be taken when handling the integrated circuit chips. They are all
v«2 sensitive to static electricity and can easily be damaged by careless handling.

sShS Jrt? the . J d )! pS m **!** pIastic carrier tubcs on conductive foam when nit
handling them. Make certain you are well grounded when handling the chips. Atari

strongly recommends that you wear a conductive grounding band (which ties from your
arm to ground) when handling the chips.

t0 dama Se from stress when being removed from or
inserted into the sockets. Always use a chip-puller when removing the chips. Do not
pry the chip out with a screwdriver or any other tooL

Failure to follow the above guidlines results in unusally high chip failur e rates and
extra expense.

ATARI Home Computer

5-1

400 POWER-UP

ATARI Home Computer

5-2

400 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
SNOWY SCREEN

ATARI Home Computer

5-3

400 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS

Go to C, next page}

ATARI Home Computer

400 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
BLACK/GREY SCREEN (contl

ATARI Home Computer

5-5

400 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
GREEN/YELLOW SCREEN

ATARI Home Computer

5-6

400 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
SOLID BLUE SCREEN

ATARI Home Computer

5-7

400 POWER-UP, PART II

ATARI Home Computer

5-8

Go to COLOR BAR
'ROUBLESHOOTING,
_Page 5-10

400 COLOR BAR
TROUBLESHOOTING

ATARI Home Computer

5-10

ATARI Home Computer

5-11

400 COLOR BAR
TROUBLESHOOTING (eont )

ATARI Home Computer

5-12

TIA TEST

ATARI Home Computer

5-13

400 GREY BAR

ATARI Home Computer

5-14

400 GREY BAR

TROUBLESHOOTING

ATARI Home Computer

5-15

400 GREY BAR
ROUBLESHOOTING (cont)

Verify that each of the following levels and/or
signal wave forms exist* before proceeding to
the next step. Use SALT II, COLOR BARS,
locked into the continuous mode._

Is there
oscillatic
on *Moti
Refer

3.58MHz
m at R158
xerboard,
figure

YES

Is there input
signal to base of
QI07 Refer Figure

YES

Is thei
signal frc
on Q10
Figure

•e output
)m collector
7 Refer

YES

NO

Swap-out X101, Q103
and Q104

NO

Trace circuit back to
previous step

NO

Trace circuit back to
previous step

ATARI Home Computer

5-16

400 GREY BAR
TROUBLESHOOTING fcont)

ATARI Home Computer

5-17

400 ANY VIDEO

ATARI Home Computer

5-18

400 ANY VIDEO
TROUBLESHOOTING

ATARI Home Computer

5-19

400 ANY VIDEO
TROUBLESHOOTING (cont)

that each of the following levels and/or
signal wave forms exist' before proceeding to
the next step. Use SALT II, COLOR BARS,
locked into the continuous mode.

iKgmi

iaiiiiiii

Is there input
signal to base of
Q107 Refer Flgurel

NO

(Trace circuit back to
previous step

A

YES

Is thei
signal frt
on Q10
Figure

-e output
collector
7 Refer

i

YES

Is there signal at
J107, Pin 1 Refer "
Figure

■

YES

Go to next page

NO

(Trace circuit back to
previous step

NO

Trace circuit back to
previous step

Home Computer

5-20

400 ANY VIDEO
TROUBLESHOOTING (contl

ATARI Home Computer

5-21

keyboard

ATARI Home Computer

5-22

KEYBOARD (cont)

TYPICAL KEYBOARD
OUTPUT

Simple made from
2104, Pin 14 ^ith
W key depressed.

SCOPE:

ATARI Home Computer

5-23

400 TONE TEST

ATARI Home Computer

5-24

400 TONE TEST (cont)

This re-runs the first
two steps of this
test

ATARI Home Computer

5-25

400 TONE TEST (cont)

ATARI Home Computer

5-26

ATARI Home Computer

5-27

400 CONSOLE SWITCH TEST

ATARI Home Computer

5-2S

400 VERIFY ROM

Verify ROM Test is
locked Into CONTIN¬
UOUS MODE and
is displaying each
ROM checksum and
the word PASS or
FAIL

ATARI Home Computer

5-29

400 VERIFY ROM (cont)

ATARI Home Computer

5-30

400 RAM

ATARI Home Computer

5-31

400 RAM (cont)

PASS

YES Go to PORT Test. !

Page 5-33 j

NO

CaU ATARI Tech Line
Specialist

Inside California
(800) 672-1466

Outside California
(800) 538-1535
(800) 538-1536

ATARI Home Computer

5-32

400 PORT

ATARI Home Computer

5-33

400 PORT (cont)

ATARI Home Computer

5-34

THIS PAGE INTENTIONALLY LEFT BLANK

ATARI Home Computer

5-35

Table 5-1
CLOCK CIRCUIT

PIN NUMBER

BOARD

FREQUENCY

SCOPE CHART

21 of J101

CPU

1.789

1

22 of J101

CPU

1.789

2

8 of Z302

CPU

1.789

2

9 of Z302

CPU

1.789

1

10 of Z302

CPU

1.789

2'

13 of Z302

CPU

1.789

3

37 of A303

CPU

1.140

4

6 of Z301

CPU

1.789

3

34 of A302

CPU

1.789

3

35 of A302

CPU

3.579

5

29 of A301

CPU

3.579

5

28 of A301

CPU

3.579

6

Collector of

Q102

800 Main Board

3.579

6

Collector of

Q104

400 Main Board

3.579

6

7 of A101

400/800 Main Board

1.789

1

25 of A102

400/800 Main Board

1.789

1

* Use Scope Waveform Legend on next
illustration of waveform.

page to see

ATARI Home Computer

5-36

Scop« Waveform 3 luS/DIV IV/DIV

Scop* Waveform 4 luS/DIV IV/DIV

Scopa Waveform 5 luS/DIV IV/DIV Scope Waveform g Iua/DIV IV/DIV

. Scope Waveform Legend

ATARI Home Computer 5-37

Keyboard

Connection

Chart

Legend

PIN CONNECTOR
NUMBERS NUMBERS

400/Z102 400/J105

800/Z103 800/J106

1. ESC

15. BREAK

29. RETURN

43 CAPS

43 • LOWS

2 ‘ 1

la CLR SET

16, TAB

30. can.

44. SHUT

3 * 2

X7. Q

31. A

45. Z

4. 5

18. W

32. S

46. X

5 - 4

19. E

33. 0

47. C

X ^

6. 5

20. a

34. F

48. V

7 - 6

21. T

33. G

49. B

8. '

22. T

36. H

50. N

23. U

37. J

51. M

10. £

24. I

38. K

52* [

•

n. 4

25. 0

39. L

53. J
•

i CIlear

26. P

40. j

T-J-

13. »««

27. t ^ -

41, * .N

53. /|\

i a DELETE

1 • BACK S

28. ♦ . 1

«. -/

56. SHIFT

57. SPACE BAR

ATARI Home Computer

5-38

C 0001 0000
D 0000 1000
E 0000 0000
RAM TEST

ERROR

COUNTER

TEST

COUNTER '

Defective RAM Boards

Defective RAM Identifier

°* teet Difference

Indicator

Description

B*

1st SK Block

B5; or

2nd 8K Block

B4 and B3

B6f or

3rd SK Block

B4 and B6

B3 and B6j

4th 8K Block

or

B4, B3 and

B6

B7j or

3th SK Block

B4 and B7

Column

Description

SK UK

DO

Z3I2

Z312

Dl

Z3U

Z311

02

2310

Z310

D3

Z50S

Z3Q9

04

Z5Q9

Z30S

03

Z307

Z307

D6

Z303

Z506

07

Z306

Z303

Figure and Table 5-2

ATARI Home Computer

5-39

Table 5-3

Port Teat Legend

ATARI Home Computer

5-40

SECTION 6

SYMPTOM CHECKLIST

The Symptom Checklist is designed to assist the experience technician arrive at a
rapid diagnosis for problems. The checklist is not intended to replace the Diagnostic
Flowchart as the primary troubleshooting guide, but rather, to supplement the

Each symptom is accompanied, by some possible causes and the best point to enter the
Diagnostic Flowchart to locate the problem.

Symptom

Possible Cause

Diagram Entry Point

Snowy Screen

SW Box, AC Adaptor

CH. Select SW, Modulator
Adjustment, RF Cable

Damage

AA

400, Page 5-3

800, Page 7-3

Black/Gray Screen

Verify +5V, -5V & +12V

Power Supplies, CR201-209,
C201-205, C210, A201, A302,
A303, A301, A103, Alii,
Z103-Z105, Q103-4, X101

BB

400, Page 5-4

800, Page 7-4

Green/Yellow Screen

Z103-5, A03, Z303 & 4
all on ROM Board

CC

400, Page 5-6

800, Page 7-6

Solid Blue Screen

A101,Q107, X101

DD

400, Page 5-7

800, Page 7-7

No Color or Bad Color

Bars with SALT II

R309 Adjust, A301-2 on

CPU Board; Alll, Q107
on Mainboard, X101,

Q103, Q104

EE

400, Page 5-9

800, Page 7-9

Modulator Adjustment

FF

400, Page 5-12

800, Page 7-12

No Color Bars on TIA Test

A301 on CPU Board

GG

400, Page 5-12

800, Page 7-12

ATARI Home Computer

6-1

Symptom

Possible Cause

Diagram Entry Point

No Gray Bars

A301, Alll, Q107

R309 Adjustment

X101, Q103 & 4

Modulator

HH

400, Page 5-14
800, Page 7-14

Upside Down Alpha/
Numerics or Player Field

A302 on CPU Board, A301

Alll,Q107

Modulator

n

400, Page 5-1
800, Page 7-14

33

400, Page 5-21
800, Page 7-21

Some Keyboard Keys Fail

Keyboard Failure

KK

400, Page 5-22
800, Page 7-22

All Keyboard Keys Fail

A101, Z103 <5c 4

LL

400, Page 5-22
800, Page 7-22

Tones Missing During

Sound or Games

A101, R160, R161, R166, R170
064, 079, 084, Q105

L101, Q106, L118, A203

MM

400, Page 5-24
800, Page 7-24

Console (Game) Switches

Will Not Function

A301 on CPU Board, R119-122
021-124

NN

400, Page 5-28
800, Page 7-28

ROM Test Failed

A401-403 on ROM Board

1403

OO

400, Page 5-29
800, Page 7-29

RAM Test Failed

See RAM test

Matrix, Figure 5

Table 5

PP

400, Page 5-31
800, Page 7-31

Hand Controllers

Will Not Work

See Port Test

Matrix, Table 5

QQ

400, Page 5-33
800, Page 7-33

ATARI Home Computer

6-2

SECTION 7

800 DIAGNOSTIC FLOWCHART

The Diagnostic Flowchart is intended to be easy to use and the primary aid when
troubleshooting the ATARI 800 Computer Console. Follow the prompts in the order
presented. When a question is asked, follow the line from that box which best applies
to the unit's situation. The flowchart leaves little to chance, it tells you when to
perform a specific test and when to replace components.

Swap Out Procedure

At many places in the diagnostic flowchart, a box tells you to "swap-out'' a chip or a
number of chips in a particular order. The "swap-out" instruction means that you
s ould replace the indicated components (one at a time) with a known good component
of the same type. The 800 should then be tested with the new, known-good component
in place to see whether the "swap-out" solved the problem being checked. If the swap-
out did not fix the problem, the known-good component should be removed, and the
original component reinserted. In this way, you avoid needlessly replacing good
components. K 6 &

CAUTION:

Extreme care should be taken when handling the integrated circuit chips. They are ail
Xer* sensitive to static electricity and can easily be damaged by careless handling.

kgg *** m thcir Pestle carrier tubes or on conductive foam when not
nandling them. Make certain you are well grounded when handling the chips. Atari
strongly recommends that you wear a conductive grounding band (which ties from your
arm to ground) when handling the chips. J

are also susceptible to damage from stress when being removed from or
inserted into the sockets. Always use a chip-puller when removing the chips. Do not
pry the chip out with a screwdriver or any other tooL

Failure to follow the above guidelines results in unusally high chip failure rates and

ATARI Home Computer

7-1

800 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS

ATARI Home Computer

7-2

800 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
SNOWY SCREEN

ATARI Home Computer

7-3

800 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS

Replace CTIA/GTIA
(A30I)

Is a clear MEMO PAD

. YES

Go to POWER-UP,

on the screen j

1

PART II, Page 7-8

Go to C # next page

ATARI Home Computer

7-4

OOP PCWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
BLACK/GREY SCREEN fcont)

ATARI Home Computer

7-5

800 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
GREEN/YELLOW SCREEN

ATARI Home Computer

7-6

800 POWER-UP

CATASTROPHIC FAILURES AND BASIC OPERATIONS
SOLID BLUE SCREEN

ATARI Home Computer

7-7

800 POWER-UP, PART II

ATARI Home Computer

7-8

COLOR BARS

ATARI Home Computer

7-9

800 COLOR BAR
TROUBLESHOOTING

ATARI Home Computer

7-10

800 COLOR BAR
TROUBLESHOOTING (cont)

Verify that each of the following levels and/or
signal wave forms exist before proceeding to
the next step. Use SALT II, COLOR BARS,
locked into the continuous node.

ATARI Home Computer

7-11

300 COLOR BAR

ATARI Home Computer

7-12

ATARI Home Computer

7-13

800 GREY BAR

ATARI Home Computer

7-14

800 GREY BAR
TROUBLESHOOTING

Swap-out A30I and
A302 on CPU Board

Do«s scr

««n look

YES

Go to ANY VIDEO,.

like Fi

f?uro 3-6

Page 7-18

NO

ATARI Home Computer

7-15

300 GREY BAR
TROUBLESHOOTING (cont)

Verify that each of the following levels and/or
signal wave forms exist before proceeding to
the next step. Use SALT II, COLOR BARS,
locked Into the continuous mode.

Swap-out X101, Q102
and Q103

ATARI Home Computer

7-16

800 GREY BAR
TROUBLESHOOTING (eont)

ATARI Home Computer

7-17

800 ANY VIDEO

ATARI Home Computer

7-18