Apple macintosh plus Service Manual

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Service Source

Macintosh Plus

K

Service Source

Basics

Macintosh Plus

Basics Overview - 1

Overview

This manual contains
complete repair procedures
for the Macintosh Plus,
shown at left.

Figure: Macintosh Plus

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Service Source

Specifications

Macintosh Plus

Specifications Introduction - 1

Introduction

Specifications information for this product can be found in this chapter and also in the

Spec Database, which you can access in one of three ways:

— Launch it directly by double-clicking the Apple Spec Database runtime alias at the top

level of the Main Service Source CD.
— Select "Apple Spec Database" from the Service Source drop-down main menu.
— Click the Acrobat toolbar icon for the database, which is near the right end of the

toolbar with the letters "SP."

Specifications Processor - 2

Processor

CPU

Motorola 68000 microprocessor

7.83 MHz
32-bit internal data bus

Specifications Memory - 3

Memory

RAM

ROM

PRAM

1 MB, expandable to 4 MB (150 ns or faster SIMMs)

128K

CMOS custom chip with 4.5 V, user-replaceable battery backup

(includes 256 bytes of memory; remembers system
parameters even with the machine switched off)

Specifications Disk Storage - 4

Disk Storage

Floppy Drive

Internal, double-sided drive: uses 3.5-in., hard-case floppy

disks—either double-sided, 800K capacity or single-sided,
400K capacity

Specifications I/O Interfaces - 5

I/O Interfaces

Floppy Drive

SCSI

Mouse

Keyboard

Serial

External drive port; DB-19 connector

One SCSI parallel port; DB-25 connector

Mouse port; DE-9 connector

Synchronous serial keyboard bus; RJ-11 connector

Two RS-422 serial ports; mini DIN-8 connectors

Specifications I/O Devices - 6

I/O Devices

Keyboard

Mouse

78 keys, including numeric keypad and cursor keys; RJ-11

connector

Mechanical tracking; optical shaft encoding at 3.54 pulses per mm

(90 pulses per in.) of travel; DE-9 connector

Specifications Sound and Video - 7

Sound and Video

Sound Generator

Video Display

Four-voice sound with 8-bit digital/analog conversion, using

22-kHz sampling rate

9-in. (diagonal) screen; 512 by 342 pixel, bit-mapped display

Specifications Electrical - 8

Electrical

Line V oltage

Frequency

Maximum Power

105–125 VAC

50–60 Hz

60 W

Specifications Physical - 9

Physical

Dimensions

Weight

Height: 13.6 in. (34.5 cm)
Width: 9.6 in. (24.4 cm)
Depth: 10.9 in. (27.6 cm)

16 lb. 8 oz. (7.5 kg)

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Service Source

Troubleshooting

Macintosh Plus

Troubleshooting General - 1

General

The Symptom Charts included in this chapter will help you
diagnose specific symptoms related to your product. Because
cures are listed on the charts in the order of most likely solution,
try the first cure first. Verify whether or not the product
continues to exhibit the symptom. If the symptom persists, try
the next cure. (Note: If you have replaced a module, reinstall the
original module before you proceed to the next cure.)

If you are not sure what the problem is, or if the Symptom Charts
do not resolve the problem, refer to the Flowchart for the product
family.

For additional assistance, contact Apple Technical Support.

Troubleshooting Symptom Charts/Video - 2

Symptom Charts

Video

No video, but audio
tone is present and
drive operates

Screen is bright and
audio is present, but
no video information
is present

1 Turn contrast control fully clockwise.
2 Check video cable connections.
3 Replace power supply board.
4 Replace neck cable.
5 Replace logic board. Retain customer’s SIMMs.

1 Replace power supply board.
2 Replace logic board. Retain customer’s SIMMs.

Troubleshooting Symptom Charts/Drives - 3

Drives

Disk ejects; display
shows disk icon with
blinking “X”

Unable to insert disk
all the way

1 Replace bad disk.
2 Replace floppy drive cable.
3 Replace floppy drive.
4 Replace logic board. Retain customer’s SIMMs.

1 Insert paper clip into small hole beside drive slot, or switch

off system power and hold mouse button down while
switching system power back on to complete eject cycle.
Then insert disk with metal slot forward and write-protect tab
on bottom.

2 Replace floppy drive.

Troubleshooting Symptom Charts/Drives

(Continued)

- 4

Does not read disks
on internal drive

Does not read disks
on external drive

Drives

1 Replace bad disk.
2 Replace floppy drive cable.
3 Replace Mylar RFI shield.
4 Replace floppy drive.
5 Verify ROMs on the logic board.
6 Replace logic board. Retain customer’s SIMMs.

1 Replace bad disk.
2 Replace floppy drive cable.
3 Replace Mylar RFI shield.
4 Replace external drive.
5 Verify ROMs on the logic board.
6 Replace logic board. Retain customer’s SIMMs.

(Continued)

Troubleshooting Symptom Charts/Drives

(Continued)

- 5

Audio tone sounds at
power on, video is
present, but drive
does not operate

Drive runs
continuously

400K drive does not
boot

Drives

1 Replace floppy drive cable.
2 Replace floppy drive.
3 Replace logic board. Retain customer’s SIMMs.

1 Replace bad disk.
2 Replace floppy drive cable.
3 Replace floppy drive.
4 Replace logic board. Retain customer’s SIMMs.

1 If logic board has Rev. A ROMs and drive stepper motor is

2 Replace floppy drive.

(Continued)

serial number F518 or higher, upgrade to Rev. B ROMs.

Troubleshooting Symptom Charts/Peripherals - 6

Peripherals

Cursor does not move 1 Connect mouse.

2 Clean mouse.
3 Replace mouse.
4 Replace logic board. Retain customer’s SIMMs.

Cursor moves but
clicking mouse
produces no response

No response to any
key on keyboard

No response from a
particular key

1 Replace mouse.
2 Replace logic board. Retain customer’s SIMMs.

1 Replace keyboard cable.
2 Replace keyboard.
3 Replace logic board. Retain customer’s SIMMs.

1 Replace keyswitch.
2 Replace keyboard.
3 Replace logic board. Retain customer’s SIMMs.

Troubleshooting Symptom Charts/Peripherals

(Continued)

- 7

Known-good
ImageWriter or
ImageWriter II does
not print

Known-good
LaserWriter does not
print

Peripherals

1 Make sure that Chooser and Control Panel are set correctly.
2 Check that system software version is compatible. Replace

software with known-good.
3 Reset PRAM.
4 Replace interface cable.
5 Replace logic board. Retain customer’s SIMMs.

1 Make sure that Chooser and Control Panel are set correctly.
2 Check that system software version is compatible. Replace

software with known-good.
3 Reset PRAM.

(Continued)

Troubleshooting Symptom Charts/Miscellaneous - 8

Miscellaneous

When turned on, the
Macintosh Plus
continuously beeps
and tries to power up

Clicking or chirping
sound

1 Perform voltage adjustment. Refer to Adjustments.
2 Disconnect internal disk drive. If this eliminates problem,

replace drive.
3 Replace logic board. Retain customer’s SIMMs.
4 Replace power supply board, logic board, and internal drive;

then turn on Macintosh. Note: Replacing only power supply

board may damage new power supply board.

1 Connect logic board cable.
2 Perform voltage adjustment. Refer to Adjustments.
3 Replace power supply board.
4 Replace logic board. Retain customer’s SIMMs.

Troubleshooting Symptom Charts/Miscellaneous

(Continued)

- 9

Smoke/odor issues
from the Macintosh
Plus

No video, no audio
tone, and no drive
operation

Miscellaneous

Replace power supply board.

1 Connect power cord.
2 Turn power on.
3 Replace power cord.
4 Check fuse.
5 Replace power supply board.
6 Replace logic board. Retain customer’s SIMMs.

(Continued)

Troubleshooting Symptom Charts/Miscellaneous

(Continued)

- 10

MacTest displays
128K/512K when
1 MB Macintosh Plus is
tested

When developer’s
switch is installed,
Macintosh Plus
sometimes resets
intermittently

Miscellaneous

Replace Macintosh Plus logic board. Retain customer’s SIMMs.

Remove switch and file it down about 1/16 inch.

(Continued)

Troubleshooting Symptom Charts/Miscellaneous

(Continued)

- 11

Macintosh Plus hangs
on startup

Macintosh Plus boots
but keyboard behaves
erratically

Miscellaneous

1 If logic board has ROMs 342-0341-A or B (ROM HI) and 342-

0342-A (ROM LO) and a peripheral device is connected to

SCSI port, peripheral device must be turned on before

powering on Macintosh Plus.

1 Replace keyboard.
2 Check that logic board grounding clip is not touching solder

points beneath logic board.
3 Replace logic board. Retain customer’s SIMMs.

(Continued)

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Service Source

T ak e Apart

Macintosh Plus

Take Apart Cover - 1

Cover

Battery
Compartment
Cover

Reset/Interrupt

Switch

Cover

No preliminary steps are
required before you begin
this procedure.

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

1 Remove the battery

compartment cover.

2 Remove the reset/

interrupt switch, if
present.

This product

Take Apart Cover - 2

3 Using a Torx screw-

driver, remove the case
screws, including the
one in the battery
compartment. Using the
pull-apart tool, gently
pry off the cover.

±

Warning:

the metal chassis may
be sharp. When moving
the computer with the
cover off, be sure to
handle the chassis
carefully.

The edges of

Take Apart Power/Sweep Board - 3

Ground Lug

Anode Cap

Discharge
Tool

Power/Sweep Board

Power/Sweep
Board

Before you begin,

• Remove the cover

• Discharge the CRT

• Remove the anode cap

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

±

Warning:

grounding wriststrap until
after discharging the CRT.

This product

Never use a

Take Apart Power/Sweep Board - 4

1 Disconnect the following

Yoke Cable

Logic Board
Cable

Neck Cable

cable connectors from
the power/sweep board:

• Yoke cable

• Logic board cable

• Neck cable

2 Remove the screw and

lockwasher that hold the
ground wire to the
chassis.

Screw &

Lockwasher

Take Apart Power/Sweep Board - 5

3

Note:

You may need to
remove the insulating
paper from the power/
sweep board to access the
mounting screws.

Remove the three
mounting screws and
washers, and lift the
power/sweep board
from the chassis.

Replacement Note:

replacing all parts except
the cover, perform the
voltage and video adjust­ment procedures. See
“Voltage” and “Video” in
Adjustments.

After

Take Apart Power/Sweep Board - 6

Replacement Note:

sending Apple a defective
power/sweep board, be
sure to include the cable that
connects to the logic board.
Make sure the contrast
control knob and battery
have been removed from the
defective board and
reinstalled onto the exchange
board.

When

Take Apart Logic Board - 7

Logic Board

Before you begin,

• Remove the cover

• Discharge the CRT

±

Logic Board

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

±

Warning:

grounding wriststrap until
after discharging the CRT.

This product

Never use a

Take Apart Logic Board - 8

1 Disconnect the following

cable connectors from
the logic board:

• Floppy drive cable

• Logic board cable

Logic Board Cable

Floppy Drive Cable

Take Apart Logic Board - 9

2

Caution:

removing the logic
board, be careful not to
damage the SIMMs —
especially the larger DIP
SIMMs that may be
installed on the board.

Pull back on the top of
the logic board, and
carefully slide out the
logic board.

When

Take Apart Logic Board - 10

3

Note:

If your replace­ment board is Rev. D
(part number 820­XXXX-D) or higher, you
should install a ground
clip. Do not use the
ground clip with any
logic board lower than
Rev. D.

Caution:

between the ground clip
and pins or solder
points on the underside
of the logic board could
cause a short, resulting
in erratic keyboard
behavior. Make sure the

Contact

Take Apart Logic Board - 11

clip does not touch any
solder points.

Install the ground clip
to the inner plastic lip
on the bottom front
bezel.

Replacement Note:

the SIMMs from the
defective logic board and
install them on the
replacement logic board.

Replacement Note:

exchanging the 512K logic
board, you must swap ROMs
to the new logic board.

Remove

When

Take Apart Logic Board - 12

Replacement Note:

replacing all parts except
the cover, perform the
voltage adjustment proced­ures. See “Voltage” in
Adjustments.

After

Take Apart CRT - 13

CRT

CRT

Before you begin,

• Remove the cover

• Discharge the CRT

• Remove the power/sweep
board

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

±

Warning:

grounding wriststrap until
after discharging the CRT.

This product

Never use a

Take Apart CRT - 14

±

Warning:

by its sides only. Do not
grasp the neck on the CRT or
touch the anode.

1 Slide the CRT socket

cable straight off the
neck of the CRT.

2 Remove the four

mounting screws and the
ground wire, and lift the
CRT off the bezel.

±

Warning:

dispose of the CRT, refer to
the CRT disposal instruc­tions in Bulletins/Safety.

Handle the CRT

If you need to

Take Apart CRT - 15

Replacement Note:

replace the CRT, perform
the voltage, video, and yoke
adjustment procedures. See
“Voltage,” “Video,” and
“Yoke” in Adjustments.

If you

Take Apart Floppy Drive - 16

Floppy Drive

Before you begin,

• Remove the cover

• Discharge the CRT

• Remove the logic board

±

Floppy Drive

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

±

Warning:

grounding wriststrap until
after discharging the CRT.

This product

Never use a

Take Apart Floppy Drive - 17

Remove the four mounting
screws, and slide the floppy
drive out of the chassis.

Replacement Note:

you install a replacement
drive, remove the dust
shield, if there is one.

Before

Take Apart Chassis - 18

Chassis

Before you begin,

• Remove the cover

• Discharge the CRT

• Remove the logic board

• Remove the power/sweep
board

• Remove the floppy drive

±

Chassis

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

This product

Take Apart Chassis - 19

±

Warning:

grounding wriststrap until
after discharging the CRT.

Remove the five mounting
screws and lift the chassis
off the bezel.

Never use a

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Service Source

Upgrades

Macintosh Plus

Upgrades Memory Upgrade - 1

Memory Upgrade

Before you begin,

• Remove the cover

• Discharge the CRT

• Remove the logic board

±

Logic Board

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

±

Warning:

grounding wriststrap until
after discharging the CRT.

This product

Never use a

Upgrades Memory Upgrade - 2

Note:

You can configure the

Logic Board

Macintosh Plus with 1 MB,

2.5 MB, or 4 MB of RAM.

The standard 1 MB configu­ration has a SIMMs resistor
installed in R8 and four

R8

256K SIMMs in both banks.
To add memory, you must
install SIMMs and remove
the SIMMs resistor.

Note:

The Macintosh Plus
requires 150-ns or faster
SIMMs. RAM speed is
indicated by the -xx number

Bank A

after the manufacturer’s
part number (-15

Bank B

indicates a 150-ns SIMM).

Upgrades Memory Upgrade - 3

Clip

one end of resistor R8

and

move

the resistor away

from the clipped lead.

R8

Bank A

Bank B

Replacement Note:

retack the resistor later, if
necessary.

You can

2.5 MB RAM Upgrade

Install

Bank A and two 256K SIMMs
in Bank B.

two 1 MB SIMMs in

4 MB RAM Upgrade

Install

Bank A and two 1 MB SIMMs
in Bank B.

two 1 MB SIMMs in

K

Service Source

Adjustments

Macintosh Plus

Adjustments Voltage - 1

Power/Sweep
Board

External Drive
Port

Voltage

You must verify voltages
after you replace the logic
board or the power/sweep
board.

Before you begin, remove
the cover.

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

This product

Adjustments Voltage - 2

±

Warning:

must make voltage
adjustments from the rear
of the compu-ter, use a
mirror to view the
computer screen. Do not
reach around the computer
to adjust the controls.

Because you

Adjustments Voltage - 3

1 Set the voltmeter to 20

volts.

2 Connect the Macintosh

voltage test cable (Apple
part number 077-

0135) to the external
drive port.

3

Caution:

Shorting the
test cable plugs to each
other can damage the
computer. Pull the
hoods over the plugs.

Connect the black

External Drive
Port

voltmeter test lead
between the voltmeter
ground terminal and the
computer chassis.

Adjustments Voltage - 4

4 Connect the orange test

cable lead to the voltage
input terminal on the
voltmeter.

Adjustments Voltage - 5

5 Switch on the computer.

6 Adjust the voltage

regulator on the power/
sweep board to between

11.90 and 12.75 volts.

7 Switch off power.

8 Disconnect the orange

Voltage
Regulator

test lead and pull the
insulated hood over the
plug.

Adjustments Voltage - 6

9 Connect the red test

cable lead to the voltage
input terminal on the
voltmeter.

10 Switch on the computer.

11 Adjust the voltage

regulator on the power/

Voltage
Regulator

sweep board to between

4.85 and 5.15 volts.

Adjustments Voltage - 7

12 Switch off power.

13 Disconnect the red test

lead and pull the
insulated hood over the
plug.

14 Repeat the tests to verify

that both voltages are

Voltage
Regulator

within the specified
tolerances.

Note:

If the power/sweep
board will not adjust so that
both voltages fall within
tolerance, replace the board.

Adjustments Yoke - 8

Yoke

If you replace the CRT, you
may need to adjust the yoke.

Before you begin:

• Remove the cover

Yoke

• Discharge the CRT

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

This product

Adjustments Yoke - 9

±

Warning:

must make yoke adjustments
from the rear of the
computer, use a mirror to
view the computer screen.
Do not reach around the
computer to adjust the
controls.

Because you

Adjustments Yoke - 10

Tilt Adjustment

Note:

If glue holds the yoke
collar in place, use an art
knife to cut through the glue.

1 Loosen the yoke clamp

Yoke Collar

Yoke Collar

screw two or three
turns.

Yoke Clamp

Yoke Clamp
Screw

Screw

2 Switch on the computer.

3 With one hand, grasp

the plastic spokes of the
yoke collar and rotate
the yoke collar until the
top and bottom edges of
the picture are parallel
with the top and bottom
of the bezel.

Adjustments Yoke - 11

4 Switch off and unplug the

computer.

5 Discharge the CRT.

6 Hold the plastic collar

in position and slowly
tighten the yoke clamp

Yoke Collar

screw so that the collar
cannot slip. Do not

Yoke Clamp
Screw

overtighten the screw.

7 Replace the cover and

switch on the computer.
Make sure the top and
bottom edges of the
picture are parallel with
the top and bottom of the
bezel.

Adjustments Yoke - 12

Centering Ring Adjustment

Note:

If glue holds the yoke
collar in place, use an art
knife to cut through the glue.

To center the picture, hold
the front centering ring
steady and move the rear
ring. Then hold the rear
centering ring steady and
move the front ring.

Centering Rings

Adjustments Video - 13

Video

You must perform the video
adjustments whenever the
CRT or the power/sweep

Power/Sweep
Board

board is replaced.

Before you begin, remove
the cover.

±

Warning:

contains high voltage and a
high-vacuum picture tube.
To prevent serious injury,
review CRT Safety in
Bulletins/Safety.

This product

Adjustments Video - 14

±

Warning:

must make video
adjustments from the rear
of the compu-ter, use a
mirror to view the
computer screen. Do not
reach around the computer
to adjust the controls.

Switch on the computer.

Because you

Adjustments Video - 15

Brightness and Contrast

1 Turn the external

contrast control fully
clockwise.

2 Turn the brightness

Brightness
Control

External
Contrast
Control

control fully counter­clockwise so that white
lines are visible. Turn
the brightness control
clockwise until the white
lines just disappear.

3 Turn the external con-

trast control 1/8 of a
turn counterclockwise.

Adjustments Video - 16

Size Adjustment

Using the alignment tool,
adjust the width control
until the raster is 7 inches

Width Control

Height Control

(177.8 mm) wide.

Using the alignment tool,
adjust the height control
until the raster is 4.7
inches (119.4 mm) high.

Adjustments Video - 17

Focus Adjustment

1 Turn the focus control

clockwise to its limit.

2 Turn the focus control

counterclockwise 1/8 of
a turn.

Focus Control

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Service Source

Exploded V ie w

Macintosh Plus

Exploded View 1

Exploded View

Internal Drive
Shield
805-0217 (800K)

800K
Floppy Drive
661-0345

Internal
Drive
Cable
590-0437

Insulator
Shield
725-0011

Front

Bezel
810-0379
810-0385

(Platinum)

CRT and Yoke

Assembly
076-0103

CRT

Socket

Cable

590-0160

Chassis
805-0766

Rear Housing

630-5211

630-5235 (Platinum)

462-3100

Power/
Sweep
Board
661-0462 110V
661-76214 220V

426-1001

Logic Board
661-0525

RFI Shroud
805-5047

426-1007

435-5002