Apple Macintosh 512k Service Manual

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Macintosh

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Basics

Macintosh

Basics Overview - 1

Overview

This manual includes repair
procedures for the earliest
Apple Macintosh
computers—the Macintosh
128K and Macintosh 512K.

Figure: Macintosh 128k/512K

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Specifications

Macintosh

Specifications Processor - 1

Processor

CPU

Motorola 68000 microprocessor

7.83 MHz
32-bit internal data bus

Specifications Memory - 2

Memory

RAM
ROM
PRAM

128K or 512K
64K
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 - 3

Disk Storage

Floppy Drive

Internal, single-sided drive; uses 3.5-in., hard-case, 400K

floppy disks

Specifications I/O Interfaces - 4

I/O Interfaces

Floppy Drive

Mouse

Keyboard

Serial

External drive port; DB-19 connector

Mouse port; DE-9 connector

Synchronous serial keyboard bus; RJ-11 connector

Two RS-232/RS-422 serial ports; DE-9 connectors

Specifications I/O Devices - 5

I/O Devices

Keyboard

Mouse

58 keys; software mapped; 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 - 6

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 x 342 pixel, bit-mapped display

Specifications Electrical - 7

Electrical

Line V oltage

Frequency

Maximum Power

105–125 VAC

50–60 Hz

60 W

Specifications Physical - 8

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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Troubleshooting

Macintosh

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 drive.
4 Replace logic board. Retain customer’s SIMMs.

1 Insert opened 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 write­protect tab on bottom.

2 Replace floppy drive.

Troubleshooting Symptom Charts/Drives

(Continued)

- 4

Drive does not eject
disk

Does not read disks
on internal drive

Drives

Insert opened 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.

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 (refer to Additional

6 Replace logic board. Retain customer’s SIMMs.

(Continued)

Procedures).

Troubleshooting Symptom Charts/Peripherals - 5

Peripherals

Cursor does not move 1 Connect mouse.

2 Replace mouse.
3 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)

- 6

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 version.
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 version.
3 Reset PRAM.

(Continued)

Troubleshooting Symptom Charts/Miscellaneous - 7

Miscellaneous

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

Clicking or chirping
sound

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

replace drive.
3 Replace logic board. Retain customer’s SIMMs.
4

Caution:

new power supply board. Replace power supply board, logic

board, and internal drive, then turn on Macintosh.

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

Replacing only power supply board may damage

Troubleshooting Symptom Charts/Miscellaneous

(Continued)

- 8

Smoke/odor issues
from the Macintosh

No video, no audio
tone, and no drive
operation

Miscellaneous

Caution:

power supply board. Replace power supply board, logic board, and
internal drive, then turn on Macintosh.

1 Connect power cord.
2 Turn on power.
3 Replace power cord.
4 Check fuse.
5

6 Replace logic board. Retain customer’s SIMMs.

Replacing only power supply board may damage new

Caution:

new power supply board. Replace power supply board, logic

board, and internal drive, then turn on Macintosh.

(Continued)

Replacing only power supply board may damage

Troubleshooting Symptom Charts/Miscellaneous

(Continued)

- 9

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

Macintosh 512K
enhanced has two RFI
shields

Miscellaneous

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

Some machines have two RFI shrouds installed. Two RFI shields
can be replaced by one RFI shield, which can be ordered as a
service part.

(Continued)

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T ak e Apart

Macintosh

Take Apart Cover - 1

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
or equipment damage,
review CRT safety and
discharge instructions in
Bulletins/Safety.

This product