Apple iMac 233 266 333MHz Service Manual

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Service Source

iMac

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Service Source

Hot Issues

iMac

Hot Issues Introduction - 1

Introduction

This chapter is designed to highlight unique or high­priority product issues that you should be aware of before
servicing the iMac computer.

This chapter alerts you to important issues and provides
pointers to other areas in the manual where more complete
information can be found. This chapter is not intended to
replace other parts of this manual; it merely provides a
pointer to pertinent information in those chapters.

To familiarize yourself with a new product family, always
read the Basics chapter in its entirety. You should also refer
to the Troubleshooting chapter for basic theory of operations
information.

Hot Issues Mixed Memory Types - 2

Mixed Memory Types

The iMac computer uses SDRAM SO-DIMMs only; EDO
memory will not work in the iMac computer. System
problems will result if EDO memory is installed. (See
“SDRAM DIMMs” in the Basics chapter and refer to the iMac
section of the Memory Guide.)

Customers are allowed to upgrade the memory in

Note:

iMac computers and may inadvertently mix EDO and SDRAM
memory. If incompatible memory types are installed, you
will hear two beeps upon startup. (See “Power-On Self
Test” in Troubleshooting for more information.)

Hot Issues Mixed Memory Types - 3

SGRAM Video Memory

The iMac computers use SGRAM video memory. Use only
SGRAM SO-DIMMs in these machines. Never install the
256K or 512K video memory DIMMs used in older
Macintosh computers. (See “SGRAM Video Memory” in the
Basics chapter.)

Error Beeps

If problems are detected upon startup, the iMac system will
sound one or more error beeps. (See “Error Beeps” in the
Troubleshooting chapter.)

Hot Issues HFS Plus Formatted Drives - 4

HFS Plus Formatted Drives

The iMac hard drive is formatted from the factory with Mac
OS Extended format, also referred to as HFS Plus. Norton
Utilities version 3.5 is not compatible with HFS Plus and
version 3.5.1 and earlier can result in hard drive
corruption and loss of all data on the hard drive. (See “HFS
Plus Formatted Drives” in the Troubleshooting chapter.)

Hot Issues Forcing a Restart - 5

Forcing a Restart

If holding down the Command, Control, and Power keys fails
to restart the iMac computer after a system hang, you can
force a restart in one of two ways:

First, try inserting a straightened paper clip in the reset
button hole. (Open the I/O door on the side of the iMac. The
reset button hole is the top hole located between the Ethernet
and modem ports and marked with a triangle symbol.)

If the reset button method doesn’t work, try the following:

1. Unplug the power cord.

2. Wait at least 30 seconds and then reconnect the power
cord.

3. Restart the iMac by pressing the power button on either
the keyboard or the front of the computer.

Hot Issues External Displays Not Supported - 6

External Displays Not Supported

Connecting an external display to the iMac is not supported by
Apple. The db-15 port on the iMac was not designed to support
an external monitor. Apple designed iMac with a very sharp,
15-inch internal display and no video-out port to connect a
second display.

Refer to Tech Info Library (TIL) article #43016, “iMac: Can I
Attach an External Display?” for more information.

Hot Issues iMac Updates - 7

iMac Updates

Apple has released a number of updates for the iMac. Refer to
TIL article #58174, iMac: When to Install Available
Updaters. This TIL article will clarify when to use the
available updates depending upon which version of iMac you
have.

Additional iMac Update articles:

• TIL article # 26115, CD Firmware Update 1.0

The CD Firmware Update reduces the amount of vibration
caused by certain CDs in the internal CD-ROM drive.

• TIL article #44005, iMac Update 1.0 Software

Apple made improvements to its Universal Serial Bus
(USB) software.

• TIL article # 58178, About iMac Update 1.1

Apple made additional improvements to its USB software.
The iMac Update 1.1 includes these new improvements

Hot Issues iMac Updates - 8

and those previously released in iMac Update 1.0. This
update improves the ability of iMac to identify USB
devices when starting up, improves the startup time
when many USB devices are connected, and enables new
USB solutions. You do not have to install iMac Update 1.0
before you install iMac Update 1.1.

• TIL article # 58370, iMac: How to Ensure Firmware

Update is Successful
If you performed the iMac firmware update and it was not
successful, this article provides some additional
assistance ensuring the update is successful.

Hot Issues CD-ROM Door Not Latching Closed - 9

CD-ROM Door Not Latching Closed

After manually ejecting CDs from the iMac CD-ROM tray (of
both /A and /B models), the eject mechanism sometimes
does not reset into a position that allows the tray door to
close properly.

Instead of replacing the CD-ROM assembly, the eject
mechanism can be manually reset with a paperclip to
correct the problem. Refer to “Resetting CD-ROM Eject
Mechanism” in Additional Procedures.

Hot Issues Revision vs. Version Part Numbers - 10

Revision vs. Version Part Numbers

Moving forward, the Service Parts database will identify
service parts (upgrades, changes, or variations) with the
word Rev. (Revision) or Ver. (Version) appended to the part
name.

For example:
661-2193 Card, Processor, 333 MHz, Rev. 3
661-2113 Board, Logic, iMac, Ver. 2

• Revision (Rev.)= A change or upgrade to the part. The

new Rev. is backward compatible and will eventually
replace the earlier part number.

• Version (Ver.)= A different variation of a similarly

functional part. The versions are not interchangeable.

Hot Issues Version 2 Service Parts - 11

Version 2 Service Parts

Listed below are the Ver. 2 iMac service parts. Exchange or
replace the Ver. 2 parts like-for-like, they are not
backward compatible. Identify the part correctly before
replacing a module or replacement part. Refer to the Service
Parts database for additional information.

• 661-2166 Analog/Video Board, Ver. 2

• 661-2167 Power Supply Board, Ver. 2

• 922-3835 Grounding Wire, CRT, Ver. 2

• 922-3836 Audio Cable, Ver. 2

• 922-3842 Video Cable, RGB, Ver. 2

• 922-3837 CRT Bottom Frame, Ver. 2

• 922-3838 CRT, Northern Hemisphere, Ver. 2

• 922-3839 CRT, Southern Hemisphere, Ver. 2

• 922-3840 CRT, Equatorial, Ver. 2

• 922-3841 Fan, 92mm, Ver. 2

Hot Issues New CD-ROM Drive Released (7/99) - 12

New CD-ROM Drive Released (7/99)

Apple recently released a new 24x CD-ROM drive service
part for five-color iMacs with 266MHz processors or
faster only. Please note that this new 24x CD-ROM, called
the Version 2, is not compatible with the 24x CD-ROM drive
in the 233MHz Bondi Blue iMacs.

Although the two iMac CD-ROM drives are identical in fit
and performance, the drives are not interchangeable. The
24X CD-ROM, Version 2, may cause data loss if used in the
233MHz Bondi Blue iMac. To ensure proper compatibility,
please order the correct CD-ROM drive when servicing an
iMac.

Hot Issues New CD-ROM Drive Released (7/99) - 13

Ordering Parts

• If you are replacing a 24x CD-ROM drive in a Bondi Blue

iMac (233MHz), order the 661-2076 CD-ROM drive.

• If you are replacing a 24x CD-ROM drive in a five-color

iMac (266MHz or greater), order 661-2207, CD-ROM
drive, 24X, Ver. 2.

Refer to the Service Parts database for additional
information.

K

Service Source

Basics

iMac

Basics - 1

Overview

Basics Product Description - 2

Product Description

The iMac is an all-in-one
product with a unique
industrial design that is
targeted specifically for the
consumer and education
market.

To view a QuickTime movie
of the iMac click here.

Basics Standard Configurations - 3

Standard Configurations

• PowerPC G3 microprocessor running at 233, 266 or

333 MHz

• System bus speed at 66 MHz

• Backside cache of 512K

• 32 MB SDRAM SO-DIMM standard, expandable to 256

MB total using 144-pin, 100 MHz or faster SO-DIMM
modules

• 6 MB SGRAM standard

• Built-in 15” CRT (13.8” viewable area)

• 4 GB (on 233 MHz) or 6 GB hard drive (on the 266 MHz

and 333 MHz)

• 24x-speed ATAPI CD-ROM drive

• 56K hardware modem

• Two Universal Serial Bus (USB) Type A ports supporting

USB devices

• One RJ-11 modem port

Basics Standard Configurations - 4

• One 10/100 BaseT Ethernet RJ-45 connector for

connection to 10 mb/s or 100 mb/s networks

• Two internal ATA connectors: one supports the hard disk

drive and one supports the CD-ROM drive

• Two 3.5 millimeter (mm) headphone jacks

• One 3.5 mm sound output port for stereo sound output

• One 3.5 mm sound input port for stereo sound input. The

sound input port supports the Apple PlainTalk
Microphone that comes with some Macintosh computers.
The sound input port also supports a standard stereo
(miniplug-to-RCA) cable adapter for connecting stereo
equipment to your computer.

• Clock/Calendar featuring CMOS custom circuitry with

long-life battery

• Fan speed thermally controlled

• Energy Saver control panel

• Built-in 2D and 3D hardware graphics acceleration via

ATI Rage IIc graphics controller ASIC

Basics Model Comparison - 5

Model Comparison

233 MHz and 266 MHz iMac Models

The following information describes the main features of the
233 MHz and 266 MHz iMac models. Note: Apple regularly
makes modest design improvements to products during their
life cycles. These changes may include minor changes to the
logic board or additions in the bundled software.

Bondi Blue (w/IrDA) M6709LL/A

• OS Software: Mac OS 8.1

• ProcessorSpeed: 233 MHz

• Reset Procedure: Reset Button on Side

• Standard SGRAM: 2 MB SGRAM Built-in

• Hard Drive: 4 GB

• Graphic Chip: ATI Rage IIc

Basics Model Comparison - 6

Bondi Blue (no IrDA) M6709LL/B

• OS Software: Mac OS 8.5

• ProcessorSpeed: 233 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 4 GB

• Graphic Chip: ATI Rage Pro

Blueberry, (no IrDA) M7345LL/A

• OS Software: Mac OS 8.5.1

• ProcessorSpeed: 266 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 6 GB

• Graphic Chip: ATI Rage Pro Turbo

Basics Model Comparison - 7

Strawberry, (no IrDA) M7389LL/A

• OS Software: Mac OS 8.5.1

• ProcessorSpeed: 266 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 6 GB

• Graphic Chip: ATI Rage Pro Turbo

Grape, (no IrDA) M7390LL/A

• OS Software: Mac OS 8.5.1

• ProcessorSpeed: 266 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 6 GB

• Graphic Chip: ATI Rage Pro Turbo

Basics Model Comparison - 8

Tangerine, (no IrDA) M7391LL/A

• OS Software: Mac OS 8.5.1

• ProcessorSpeed: 266 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 6 GB

• Graphic Chip: ATI Rage Pro Turbo

Lime, (no IrDA) M7392LL/A

• OS Software: Mac OS 8.5.1

• ProcessorSpeed: 266 MHz

• Reset Procedure: Front Power Button

• Standard SGRAM: 2 MB SGRAM Built-in + 4 MB SGRAM

DIMM

• Hard Drive: 6 GB

• Graphic Chip: ATI Rage Pro Turbo

Basics Model Comparison - 9

333 MHz iMac Models

On April 14, 1999 Apple announced the 333 MHz iMac.
There were no other configuration changes to these
computers other than the processor speed.

• Blueberry, M7440LL/A

• Strawberry, M7441LL/A

• Grape, M7442LL/A

• Tangerine, M7443LL/A

• Lime, M7444LL/A

Basics New Technologies - 1 0

New Technologies

Infrared Communication

The iMac (models M6709LL/A and M6709LL/B) come with
built-in 1-megabit infrared technology for easy, wireless
LAN access and file sharing with similarly equipped
systems. The iMac logic board has one IrDA (Infrared Data
Association) compliant connector that offers a maximum
transfer speed of 4 MB/sec (AppleTalk and TCP/IP).

The iMac also allows users to switch to the IRTalk protocol
by using the Infrared Control Panel. The iMac can therefore
communicate with other IRTalk-capable devices (such as
Macintosh PowerBooks) using the IRTalk protocol at a speed
of 230 kB/second (AppleTalk Only).

For information about whether or not iMac computers can
communicate with HP printers, contact Hewlett Packard.

Basics New Technologies - 1 1

For information about whether iMac computers can
communicate with other third-party IrDA compliant
devices, contact the manufacturer of the third-party device.

The iMac supports the following Apple devices on the IrDA
channel:

• PowerBook 2400 and 3400

• Macintosh Powerbook G3

IrDA vs. IRTalk

There are two main differences between IRTalk and IrDA:

1. IrDA is an industry standard, while IRTalk is an Apple­only technology.

2. IrDA supports TCP/IP and AppleTalk, whereas IRTalk
only supports AppleTalk.

The Infrared Control Panel gives information about any

Basics New Technologies - 1 2

Infrared connections that are established as well as what
type of infrared the iMac is currently set to use.

For infrared options to work there are three drivers that
must be in the Control Panels or Extensions folder. They are:

• Infrared Control Panel

• IrDALib Extension

• IrLanScannerPPC Extension

If these icons are not present or disabled, you will not be
able to make infrared connections from the iMac.

If you have used infrared communications with other Apple
products, you will notice a difference with iMac. The lens in
the rear of the iMac has been updated to support IrDA. The
new lens has about a 30 degree viewing angle. There is also a
minimum 3-foot distance for recognizing other Infrared
devices.

Basics New Technologies - 1 3

USB Support

Universal Serial Bus (USB) is a new device communication
standard developed by the computer and telecommunication
industries. USB provides a powerful, hot-swappable, “true
plug-and-play” interface between a host computer and add­on peripheral devices. (
you can plug in, use, and unplug devices without having to
shut down the host computer.)

USB devices can include keyboards, mice, joysticks,
telephones, scanners, printers, security dongles,
microphones, speakers, floppy drives, cameras, modems,
CD-ROM drives, etc. USB technology can provide support for
anticipated future devices as well, such as digital subscriber
line (DSL) modems, cable modems, and MPEG video devices.

USB was designed to overcome limitations of earlier
peripheral connection technologies. USB allows end users to

: “Hot-swappable” means that

Note

Basics New Technologies - 1 4

connect peripheral devices to a host computer on the fly,
without having to hassle with

• Shutting down/restarting the computer

• Opening the computer case

• Installing a card

• ID conflicts

• Termination issues

• Loading device drivers (although some devices may

require a one-time driver installation).

In addition, USB provides the user with

• A “tiered star hub” network topology (see diagram later

in this section) allowing for the connection of up to 127
devices per host computer

• Two simple, standardized plugs for the broad range of

devices

• Power for some devices directly through the USB cable

• Two data speeds for devices: 1.5 and 12 megabits per

Basics New Technologies - 1 5

second (Mbps)

• Automatic adjustment of bandwidth allocation among

devices.

Basics New Technologies - 1 6

USB devices use two types of plugs, Type A and Type B:

Figure 1: USB Plug Types

Basics New Technologies - 1 7

The Type A plug (pictured on the left) connects to the host
computer or an upstream hub. The Type B plug (pictured on
the right) connects downstream to the USB device. Some
devices, such as mouse devices, have a Type B plug built into
the device.

“Upstream” means moving up the device chain, in

Note:

the direction of the host computer. “Downstream” means
moving down the device chain, away from the host computer.
Figure 2 on the next page illustrates this concept.

High speed connections (12 Mbps) use shielded cabling to
reduce interference at higher connection rates, while low
speed (1.5 Mbps) may not. Each connector has four pins,
two for power and two for data.

Basics New Technologies - 1 8

Figure 2: Defining Upstream/Downstream Terms

Basics New Technologies - 1 9

Benefits of USB Technology

The advantages of USB technology include hot-swapping
capability, auto-configuring, and ease of use. For example,
with just one available USB socket, a customer could:

• plug in a scanner, scan a photo, unplug the scanner

• then plug in a printer, print that photo, unplug the

printer

• then plug in a modem, e-mail the photo to a friend,

unplug the modem

• then plug in a storage drive, backup the photo file,

unplug the drive

all without having to restart the host computer, or even go
into sleep mode.

USB also provides a faster connection and a larger number of
ports than ADB or serial options.

Basics New Technologies - 2 0

How a USB Device is Installed and Used

A USB network is made up of the following components:

• An operating system that supports USB. (Both iMac and

Windows 98 support USB.)

• A host, typically a controller chip set residing in the

personal computer, controls the USB system and allocates
bandwidth per device. There is only one host per USB
network, and as such USB is designed for connecting
peripherals to the computer, not computers (or hosts) to
each other. This explains why USB will not replace local
area networking (for example, 10BaseT Ethernet),
though their data transfer speeds can be comparable.

The USB host typically provides two or three Type A ports
via an internal hub (inside the computer case) for devices
and hubs to connect to.

Basics New Technologies - 2 1

Type A Ports

FIgure 3: USB Ports

Basics New Technologies - 2 2

Note:

Type A ports (as shown in the previous illustration)
are only available from hubs. If a device (like a keyboard or
display) has Type A ports for additional devices to connect
to, it must have an internal hub. This information is good to
know when you need to identify, map out, and troubleshoot
hub and device connectivity.

USB ports, cables, and plugs are often labeled with the

Note:

standard USB symbol shown in the following illustration.

Figure 4: Standard USB Symbol

Basics New Technologies - 2 3

• Hubs, which serve as connection points for devices. Hubs

also provide device detection, speed matching, and power
control. Hubs connect to the host using the 12 Mbps
connection speed. Hubs may be “bus-powered” by the
USB, or be “self-powered” by an external power source
(like an AC adapter). Only hubs can connect to the host.
Hubs can also connect to other hubs, providing expansion
to the 127 device limit (see the example tree diagram
below). Hubs can be freestanding, or embedded in other
items (displays, keyboards, etc.). Most freestanding
external hubs provide 4 Type A ports, but this is not a
always the case.

When troubleshooting power errors that bus-

Note:

powered hubs can't be connected to bus-powered hubs,
since not enough power is provided to power the device
ports. Instead, to extend the USB properly, users should
alternate self-powered and bus-powered hubs.

Basics New Technologies - 2 4

• Devices, which connect to hubs and provide expanded

functionality to the computer. Devices connect to the host
using either the 1.5 or the 12 Mbps connection speed.
Like hubs, devices may be “bus-powered” by the USB
network, or be “self-powered” by an external power
source. Devices can only connect to hubs. Devices cannot
connect directly to devices, but looks can be deceiving,
since some devices are combined with hubs in the same
physical case.

Basics New Technologies - 2 5

The following tree diagram shows an example of a USB
network:

Basics New Technologies - 2 6

Root Tier

Host

Can both Reside
inside CPU Case

Hub

Tier One

Device

Device

Device

Device

Hub

Tier Tw o

Hub

Hub

Tier Three

Device

Tier Four

Figure 5: USB Network Tiers

Device

Device

Basics New Technologies - 2 7

USB Connectivity Rules

Following are the rules for USB connectivity:

• The maximum number of devices that can be connected to

a single USB hub is 127 devices. (Note: A keyboard with a
built-in trackball counts as two devices.)

• The maximum number of tiers allowed is six. This can be

tricky to track sometimes, since hubs can be hidden in
CPU cases, displays, keyboards, etc.

• Bus-powered hubs can't be connected to bus-powered

hubs due to power limitations. A keyboard with an
internal hub is a good example of a bus-powered hub.

• The maximum cable length allowed for 12 Mbps devices

is 5m, and the cable must be shielded. The maximum
cable length allowed for 1.5 Mbps devices is 3m, and the
cable is typically unshielded.

Basics New Technologies - 2 8

Installing and Using a USB Device on a USB-Capable Mac OS
Computer

Carry out the following steps to install and use a USB device
on a USB-capable MacOS computer:

1. Make sure your device is Mac-OS approved. Although

USB devices should all conform to the USB specification,
some developers' devices do not follow spec. As a result,
they need specially written drivers. Also, the current
version of Mac OS support for USB does not yet support
USB devices like microphones and speakers. In any case,
customers should purchase only USB devices that have
the Mac-OS seal of approval:

2. If necessary, run the installer for the device driver.

Check the instructions that came with the device for
details.

3. Provide external power if needed for the device. Check

Basics New Technologies - 2 9

the instructions that came with the device for details.

4. Plug the device in to an available hub port. The device

should be sensed automatically, the driver should
automatically load, and the device should then be ready
for use. When you are finished using the device, you can
leave it plugged in, or unplug it to free up the port.

Basics New Technologies - 3 0

Features

Basics Modem - 3 1

Modem

The iMac computer features a built-in 56K hardware
modem. This internal modem supports both K56-Flex and
V.90 communications protocols.

Modem Performance Issues

To be able to accomplish 56K connections, your Internet
Service Provider or service you are connecting to must have
digital connections to the Telephone Company, and then
install special 56K digital modems which can use these
connections. By using a digital connection, a digital-to­analog-to-digital conversion can be eliminated at their end,
which allows support of a higher speed transmit protocol
from their site. This means that users will not get 56K
connections if one user calls another user directly. Because
they lack the digital connections, they will connect at around

33.6 connections consistently.

Basics Modem - 3 2

If you have a modem that supports this higher speed
protocol, you can theoretically download data at up to
56,000 bps. With these 56K protocols, however, your
upload speed is still going to occur at V.34 speeds (up to

33.6) because the digital equipment is only on your ISP's
end.

While the technology theoretically can achieve download
speeds up to 56 kbps, current FCC rules limit the power
output of modems such that you probably will not achieve
that maximum speed. The maximum speed possible under
this regulation is 53 Kbps.

Users who have unstable phone lines are finding they still
can't get speeds above what they were getting with their
V.34 28.8/33.6 modem. Remember that your phone line
quality is the most important factor here, and many people
who have poor quality telephone line conditions will almost

Basics Modem - 3 3

always connect at 33.6 speeds or less.
Also, line noise will be a major factor on how fast your 56K

modem connects. For 33.6 Kbps or slower modems, line
noise is still a factor, but it is much less of an issue for
achieving good connections.

Basics CD-ROM Drive - 3 4

CD-ROM Drive

The CD-ROM drive is located beneath the screen on the front
of the iMac. To open the tray, press the button in the middle
and carefully pull open the tray until it lightly clicks. To
close the drive, push the tray until it is completely closed
and locked into place.

CD Adapter Board

The CD adapter board screws onto the back of the CD-ROM
drive. A ribbon cable attaches to the CD-ROM adapter board
and plugs into connector J14 on the logic board.

The CD adapter board is part of the CD-ROM module and
should not be removed or replaced.

Basics Power Filter Board - 35

Power Filter Board

The power filter board is an EMC filtering board, which is
mounted on the logic board/mass storage chassis. It controls
the DC power supply connection from the enclosure and sits
between the power supply board and the logic board.

It is highly unlikely that the power filter board will ever
fail, but information about this board is included in the “No
Power” section of the Troubleshooting chapter.

Basics Audio/Video Interconnect Board - 36

Audio/Video Interconnect Board

The audio/video interconnect board provides a bridge
between the logic board and the audio on/off, video, and IrDA
boards. The audio/video interconnect board sits between the
logic board and the logic board/mass storage chassis.

For example, one cable runs from the IrDA board to the
audio/video interconnect board; then a separate cable runs
from the opposite side of the audio/video interconnect board
to the IrDA connector on the logic board. The same is true for
connections between the logic board and the video and audio
on/off boards.

Note: Apple does not support connecting an external monitor
on the iMac. Connecting an external monitor will void the
warranty. Refer to TIL article #43016.

Basics Power Supply Board Fuse - 37

Power Supply Board Fuse

There is a fuse on the AC line on the iMac power supply
board. The fuse is located at F901 (near the bottom right
corner of the installed power supply board as you face the
back side of the board). Instructions for how to test the fuse
are included in the “Testing for Power” section of the
Troubleshooting chapter.

Basics Graphics Controller - 3 8

Graphics Controller

The graphics subsystem on the iMac logic board is designed
with the ATI Rage IIc graphics controller ASIC. The RAGE IIc
ASI contains 2D and 3D acceleration engines, a bidirectional
digital video port, a front-end scaler, a back-end scaler,
CRT controller, and PCI bus master capability.

The graphics subsystem features an industry standard
SGRAM SO-DIMM connector in addition to 2 MB of SGRAM
soldered to the logic board. The SGRAM SO-DIMM can
accommodate SO-DIMM sizes of 2 MB and 4 MB, for a total
SGRAM capacity of 6 MB.

Basics Sound - 39

Sound

The 16-bit stereo audio circuitry provides high-quality
sound input and output through the built-in microphone and
speakers. The user can also connect external input and
output devices by way of the sound input and output jacks.

The sound system supports sample sizes up to 16 bits at a
sample rate of 44.1 kHz.

Basics Sound Input - 4 0

Sound Input

The sound system accepts inputs from three possible
sources:

• Built-in microphone

• External stereo sound input jack

• Sound from internal CD player

Basics Sound Output - 4 1

Sound Output

The sound system sends computer-generated sounds to the
built-in speakers, the sound output jack, and the headphone
jacks. The sound system provides user-selectable SRS 3D
stereo enhancement.

Basics Video Display - 4 2

Video Display

The built-in video display uses a 15-inch CRT and supports
three resolutions. The table below lists the resolutions and
pixel depths supported with the standard 2 MB of SGRAM and
with expanded SGRAM.

Resolution: 640 x 480

• Vertical rate: 117.233 Hz

• Pixel depth (2 MB SGRAM): 32 bits

• Pixel depth (4 or 6 MB SGRAM): 32 bits
Resolution: 800 x 600

• Vertical rate: 94.97 Hz

• Pixel depth (2 MB SGRAM): 32 bits

• Pixel depth (4 or 6 MB SGRAM): 32 bits

Basics Video Display - 4 3

Resolution: 1024 x 768

• Vertical rate: 75.03 Hz

• Pixel depth (2 MB SGRAM): 16 bits

• Pixel depth (4 or 6 MB SGRAM): 32 bits

Basics Backside Cache - 4 4

Backside Cache

Backside cache is a significant architectural design change
from earlier PowerPC processors. The main advantage of the
backside cache architecture is the speed of the dedicated
CPU-to-L2 cache interface. Using the dedicated bus allows
the CPU to access the fast L2 cache storage through a high­speed bus without addressing the slower system bus or
competing with other devices attached to the system bus. In
comparison, a “far-side” cache running on the system bus
would limit that SRAM interface to 50MHz.

The PowerPC G3 microprocessor interfaces with SRAM
storage via a dedicated bus running at various multiples of
the core PLL CPU speed. With high speed L2 SRAM and a
dedicated L2 bus, the CPU can access stored information up
to the speed of the processor clock. L2 access is determined
by the clock ratio setting. For example, with a 250 MHz

Basics Backside Cache - 4 5

PowerPC G3, and a 2.5 L2 bus ratio, the backside cache bus
speed will be 100MHz, twice the speed of the system bus.

Basics Memory - 46

Memory

SDRAM DIMMs

The iMac computer uses SDRAM in a SO-DIMM slot that is
smaller than the RAM slots for previous desktop Power
Macintosh computers. There are two SDRAM SO-DIMM slots.
The bottom slot contains the pre-installed 32 MB SO-DIMM.
The top slot is user installable.

If a customer orders extra RAM via the build-to-order
(BTO) program, that RAM will be installed in the upper
slot. This means that a customer may get their iMac with
both RAM slots populated. In addition, end users are
permitted to install/upgrade their own RAM on the iMac
computer. Therefore, you should not assume there is a free
RAM slot in the customer’s computer.

Basics Memory - 47

Maximum SDRAM supported

• 233 MHz/A iMac: Maximum size supported is 64 MB per

slot, totaling 128 MB. This can be achieved by installing
a 64 MB module in the upper slot and a 64 MB module in
the lower slot.

• 233 MHz/B iMac:

per slot, totaling 256 MB. This can be achieved by
installing a 128 MB module in the upper slot and a 128
MB module in the lower slot.

• 266 MHz iMac:

slot, totaling 256 MB. This can be achieved by installing
a 128 MB module in the upper slot and a 128 MB module
in the lower slot.

• 333 MHz iMac: Maximum size supported is128 MB per

slot, totaling 256 MB. This can be achieved by installing
a 128 MB module in the upper slot and a 128 MB module
in the lower slot.

Maximum size supported is128 MB

Maximum size supported is128 MB per

Basics Memory - 48

The lower RAM expansion slot will only accommodate SO­DIMMs that are 1.0 inch to 1.5 inches in height. A 2.0-inch
DIMM will not physically fit into the slot and cannot be used.
If a 128 MB DIMM existed that was smaller than 1.5 inches,
it would work in the lower expansion slot.

EDO SO-DIMM RAM modules are not compatible with the
iMac computers. If a customer uses an EDO SO-DIMM, the
unit will boot fine but will not show any RAM increase in the
“About this Computer” window.

If EDO memory is mixed with SDRAM memory, the

Note:

computer will sound two beeps at startup. (See “Power-On
Self Test” in Troubleshooting for more information.)

SGRAM Video Memory

The iMac logic board comes with 2 MB of Synchronous
Graphic RAM (SGRAM) video memory soldered on. The logic

Basics Memory - 49

board also contains a video memory expansion slot that
accepts a Small Outline DIMM (SO-DIMM) to increase video
memory up to a maximum of 6 MB. Apple supports a 4 MB
SGRAM SO-DIMM that is 32-bit wide, 144-pin, fast­paged, 83 MHz/12 ns cycle time or faster.

Important:

Use only SGRAM SO-DIMMs. Never use the 256K
or 512K video memory DIMMs used in older Macintosh
computers.

Basics Memory - 50

Views

Basics Front View - 5 1

Front View

Basics Rear View - 5 2

Rear View

Basics Left Side View - 53

Left Side View

Basics Right Side View - 54

Right Side View

Basics Internal Locator - 5 5

Internal Locator

Basics iMac Logic Board - 56

)

iMac Logic Board

Processor Card

J18

J16 

Video 

J1

Hard Drive

Connector



J19

J20



J17



*Modem

Connector

*Power Filter

Connector

SGRAM

Slot

Graphics

Chip

Product

ID Label

J15
HD Power
Connector

*(Connector on underside of Logic Board

Connector

J13
CD-ROM
Connector

CUDA 
Reset Button

Modem

Ethernet

USB
Speakers

Microphone

J6 IrDA
Connector

Battery

J14 

Audio

Connector

Basics I/O Panel - 5 7

Type A Ports

(USB)




Sound In

Sound Out

Ethernet

Reset

Interrupt

Modem

I/O Panel

Basics I/O Panel - 5 8

Repair Strategy/Warranty

Basics Strategy and Ordering - 59

Strategy and Ordering

The iMac computer is to be serviced through module
exchange and parts replacement. Apple Computer offers
standard carry-in service only on the iMac computers (with
the exception of US customers who purchase the AppleCare
Service Plan, covered later in this section).

Apple Service Providers planning to support the computer
systems covered in this manual may purchase Service
modules and parts to develop servicing capability. To order
parts, use the AppleOrder (US only) or ARIS (Canada only)
systems and refer to the iMac “Service Price Pages.”

Basics Strategy and Ordering - 60

Large businesses, universities, and K-12 accounts must
provide a purchase order on all transactions, including
orders placed through the AppleOrder (US only) or ARIS
(Canada only) systems.

USA Ordering

US Service providers not enrolled in AppleOrder may fax
their orders to Service Provider Support (512-908-

8125) or mail them to

Apple Computer, Inc.
Service Provider Support
MS 212-SPS
2323 Ridgepoint Drive
Austin, TX 78754

Basics Strategy and Ordering - 61

For US inquiries, please call Service Provider Support at
800-919-2775 and select option #1.

Canadian Ordering

Canadian Service providers not enrolled in ARIS may fax
their orders to Service Provider Support in Canada (1­800-903-5284). For Canadian inquiries, please call
Service Provider Support (800-217-9517).

Basics Warranty - 62

Warranty

Following are the details of the warranty/AppleCare
program for the US and Canada.

US Only

The iMac computers are covered under the Apple One-Year
Limited Warranty. The AppleCare Protection Plan is also
available for these products. Service Providers are
reimbursed for warranty and AppleCare Protection Plan
repairs. For pricing information, refer to Service Price
Pages.

Basics Warranty - 63

Canada Only

The iMac computers are covered under the Apple One-Year
Limited Warranty. The AppleCare Protection Plan is also
available for these products. Service Providers are
reimbursed for warranty and AppleCare Protection Plan
repairs. For pricing information, refer to Service Price
Pages.

K

Service Source

Specifications

iMac

Specifications Introduction - 1

Introduction

Specifications information for this product can be found in the Spec Database, which you can
access at Service Source Online (http://service.info.apple.com) or on Service Source CD.

Spec Database at Service Source Online

From the Service Source Online home page, click Troubleshoot and Repair to access the main
repair procedures page. Then click either Apple Spec in the navigation table in the upper
right corner of the page, or click Apple Spec Database from the list of reference tools below.

Spec Database on Service Source CD

Open the CD and double-click the Apple Spec Database alias located at the top level of the CD.

K

Service Source

Troubleshooting

iMac

Troubleshooting General - 1

General

Troubleshooting General/ Block Diagram - 2

Block Diagram

The following illustration provides an overview of the iMac
internal components and shows how they are connected.

RGB Cable

Fan

R

P508
P514

P1

Power /Headphone

P2

Audio Cable
(5 connectors)

L

P701

Board

CRT Power Cable

P702

Analog

Board

Power

Filter

Board

Internal

Mic

P502

P506

P505

J18

HD

Power

J6

P301

Power Cable

Processor Board

Logic Board

J15

J16

J17

Video

J2

A/V Interconnect

Board

J5

Video Board

P302 P303P306P304 P305

CRT

J13

J14

Audio

J1

Modem
Ethernet

USB

IrDA Ribbon Cable

J3

J4

AC

P908

P913

Keyboard

Power
Supply

Board

On/Off

CD/HD Data Cable
with Ferrite Bead

IrDA Bd

CD-ROM Interconnect Board

CD-ROM Drive

Hard Drive

Troubleshooting General/ Power Flow - 3

Power Flow

Power is controlled in the iMac system by the power supply
board. Once the unit is plugged in, power flows from the AC outlet
at the wall to the AC inlet on the power supply board. From there,
the power flows through the power filter board and on to the
analog/video board, the logic board, and all its attached
components.

Click here
iMac.

to view an animation of how power flows through the

Power Supply Board Fuse

There is a fuse on the AC line on the power supply board (at
F901) that can be replaced if the computer has no power. (Refer
to the “No Power” symptom for a full troubleshooting scenario.)

Before replacing the fuse, you should do a continuity test with an
ohm meter. If the ohm meter registers “0”, the fuse is good. If
the meter registers “infinite,” the fuse should be replaced.

Refer to “Testing for Power” later in this chapter for
instructions on how to check the power supply board fuse. Refer to
“Logic Board” in the Take Apart chapter to locate the fuse on the
power supply board.

Troubleshooting General/ Testing for Power - 4

Testing for Power

The iMac requires trickle voltage (+5 TRKL) in order to power­on. If you are experiencing power problems in the iMac unit, you
will want to test for trickle power at various points in the system
to pinpoint the location of the problem and to determine whether
or not the power supply is functioning normally. If you have
trickle power in the system, the odds are your power supply is
OK.

In general, you should test for power at the AC outlet first. Next,
it is best to start at the end (in this case, the logic board) and
trace power backwards through the system. In this way, you will
be able to immediately pinpoint which component is failing.

It is highly unlikely that the power filter board will fail;

Note:

therefore, you need not test for power at this component.
Following is the order in which you should test for power in the

system: At the 1) AC outlet, 2) logic board, 3) power filter
cable, 4) power supply board, and 5) power supply fuse.

Testing for power requires that you remove certain parts from
the computer. Refer to the Take-Apart chapter for instructions on
removing parts.

At the AC Outlet

First, unplug the keyboard from the computer. Then, using a
known-good power cord, power-on the system using the power
button on the front of the computer. If the system powers on, you
can assume the AC outlet is good and the problem is with the
keyboard. If the system still won’t power on, try connecting to a
different AC outlet. If the unit powers on this time, you most
likely have a problem with the AC outlet. If you still have no
power, you will need to test for power at internal points inside the
iMac.

At the Logic Board

With the iMac placed with the CRT face down on a soft surface,
remove the bottom access cover and then remove the logic board/
mass storage chassis to access the logic board.

: You will need a volt meter to test for power on the logic

Note

board. Refer to the picture on the next page to locate the necessary
test point referenced in the following procedure.

Troubleshooting General/ Testing for Power - 5

Plug in the computer, but leave the iMac powered OFF. Ground the
black probe on the volt meter (by inserting it into the metal
chassis). With one hand behind your back, touch the red probe on
the volt meter to the positive lead of capacitor C28 on the logic
board (see the photograph on the next page) to see if you have +5V
on the logic board. A +5V reading on the logic board means the
power supply is providing the necessary trickle voltage to logic
board.

Testing for Power at the Logic Board

Troubleshooting General/ Testing for Power - 6

At the Power Supply to Power Filter Cable

First remove the bottom access cover to reach the cables feeding
into the logic board/mass storage chassis.

: You will need a volt meter to test for power at the power

Note

supply to power filter cable. Refer to the picture below to locate
the necessary test point referenced in the following procedure.

Unplug the power supply to power filter cable from the back side
of the logic board/mass storage chassis. Plug in the iMac, but
leave it powered OFF.

: You may need to unplug the RGB video cable to access the

Note

power cable.

Testing for Power at the Power Supply to Power Filter Cable

Ground the black probe on the volt meter to the computer’s metal
chassis. Carefully touch the red probe to the first pin on the top
right end of the power cable (the top being the side with the
connector key on it). If you get a +5V reading, you know you have
power from the power supply and that the power cable is likely
OK. There still could be a problem with other pins on the cable,
however.

Troubleshooting General/ Testing for Power - 7

At the Power Supply Board

The procedure below tests for +5 V on the original iMac

Note:

power supply board, 661-2081. Refer to the procedure on the
next page to test for +5 V on the Version 2 (661-2167) power
supply board.

First remove the top access cover and then remove the CRT EMI
shield to reach the power supply board.

±

Warning:

exposed and the unit plugged in. Use extreme caution and avoid
touching the exposed power supply to avoid any shock hazard when
working on an open unit.

You will need a volt meter to test for power on the power supply
board. Refer to the picture below to locate the necessary test
points on the power supply.

Ground the black probe of a volt meter to the computer chassis.
Plug in the iMac, but leave it powered OFF. Then, being careful not
to short together any pins, touch the red probe on the volt meter to
pin 24 on the power supply board and test for +5V.

In this next procedure, the power supply will be

Testing for Power at the Power Supply Board

Troubleshooting General/ Testing for Power - 8

The procedure below tests for +5 V on the Version 2 (661-

Note:

2167) power supply board.
First remove the top access cover and then remove the CRT EMI

shield to reach the power supply board.

±

Warning:

exposed and the unit plugged in. Use extreme caution and avoid
touching the exposed power supply to avoid any shock hazard when
working on an open unit.

You will need a volt meter to test for power on the power supply
board. Refer to the picture below to locate the necessary test
points on the power supply board.

Ground the black probe of a volt meter to the computer chassis.
Plug in the iMac, but leave it powered OFF. Then, being careful not
to short together any pins, touch the red probe on the volt meter to
pin 3 on the power supply board and test for +5V.

In this next procedure, the power supply will be

Testing for Power on the Version 2 Power Supply Board

Troubleshooting General/ Testing for Power - 9

At the Power Supply Board Fuse

First remove the top access cover and then remove the CRT EMI
shield to access the power supply board.

±

Warning:

at the power supply board fuse.

You will need an ohm meter do a continuity test on the power

Note:

supply board fuse. Refer to the picture on the next page to locate
the necessary test point referenced in the following procedure.

Unplug the computer to take this reading. Using an ohm meter,
touch the red and black probes to the two metal points at location
F901 and check for continuity (reading of “0”). Any other
reading than “0” indicates a bad fuse, which should be replaced.
The figure on the following page shows how to take the reading.

You must unplug the iMac to test do a continuity test

Testing the Power Supply Board Fuse

Troubleshooting General/ The Cuda Chip - 10

The Cuda Chip

The Cuda is a microcontroller chip. Its function is to:

• Turn system power on and off.

• Manage system resets from various commands.

• Maintain parameter RAM (PRAM).

• Manage the real-time clock.
Many system problems can be resolved by resetting the Cuda chip

(see the Symptom/Cure tables for examples). Press the Cuda
reset button on the logic board to reset the Cuda chip. (The Cuda
reset button is located on the back edge of the logic board between
the modem port and the processor module. Refer to the Logic Board
Diagram in the Basics chapter for location information.) If you
continue to experience system problems, refer to “Resetting the
Logic Board” later in this chapter.

Troubleshooting General/ Resetting the Logic Board - 11

Resetting the Logic Board

Resetting the logic board can resolve many system problems (see
the Symptom/Cure tables for examples). Whenever you have a
unit that fails to power up, you should follow this procedure
before replacing any modules.

1. Unplug the computer.

2. Disconnect the cable that runs from the power supply to the
power filter board on the bottom side of the logic board/mass
storage chassis.

3. Press the Power On button on the front of the unit.

4. Remove the logic board/mass storage chassis from the unit.

5. Remove the battery from the logic board.

6. Wait at least 10 minutes before replacing the battery.

7. Make sure the battery is installed in the correct +/-
direction.

8. Reassemble the computer and test the unit.

This procedure resets the computer’s PRAM. Be sure to

Note:

check the computer’s time/date and other system parameter
settings afterwards.

Troubleshooting General/ Power-On Self Test - 1 2

Power-On Self Test

There is a power-on self test that resides in the ROM of the iMac.
This test automatically runs whenever the iMac is powered on
after being fully shut down (the power-on self test does not run if
the machine is only restarted).

If a problem is detected during the test, you will not hear a
normal startup chime. Instead, the system will beep as explained
below. Refer to “Error Beeps” later in this chapter for
instructions on how to troubleshoot and repair an iMac that sounds
error beeps at startup time.

Following is a definition of what the error beeps at startup time
signify.

•

1 Beep:

•

2 Beeps:

SDRAM SO-DIMMs and does not accept EDO memory).

•

3 Beeps:

•

4 or 5 Beeps:

ROM. The ROM (which is located on the processor module)
is bad.

No RAM is installed or detected.

EDO memory is installed. (The iMac ships with

No RAM banks passed memory testing.

Bad checksum for the remainder of the boot

Troubleshooting General/ Video Flow - 1 3

Video Flow

Video signals begin on the logic board at connector J16 and travel
to connector J2 on the A/V interconnect board. The video signals
then travel out from connector J5 (on the opposite side of the A/V
interconnect board) and continue on via the internal RGB cable to
P301 on the analog/video board. From there, the signals are
transmitted to the CRT where they are displayed on the screen.

Click here
through the iMac.

to see an animation of how the video signal travels

Sound In Flow

Sound coming into the iMac system originates at the internal
microphone located in the top front area of the system, or through
an external microphone connected to the logic board.

If the sound signals originate at the internal microphone, they
travel along the long internal audio cable to connector J6 on the

A/V interconnect board. The signal is then transmitted to
connector J1 on the back side of the A/V interconnect board,
travels via the short internal audio cable, and finally arrives at
connector J14 on the logic board.

If the sound signals originate at an external microphone, they
travel directly from the external microphone to the microphone
(sound in) connector on the logic board.

Click here to see an animation of how the sound in signals travel
through the iMac.

Troubleshooting General/ Sound Out Flow - 14

Sound Out Flow

The iMac has three sound out paths: to the built-in speakers, to
the sound output jack, and to the headphone jacks.

To transmit sound out the internal speakers, the sound signals
must travel (via the short internal audio cable) from the J14
audio connector on the logic board to the J1 connector on the A/V
interconnect board. From there, the signals are transmitted to the
J6 connector on the other side of the A/V interconnect board. And
then the sound out signals travel via the long internal audio cable
to the internal speakers.

Sound that is transmitted to the external speakers travels directly
from the sound out connector on the logic board to the external
speakers via their external cable hookup.

Click here
through the iMac.

to see an animation of how the sound-out signals travel

Processor Module

The iMac logic board comes with a removable processor module,
which can be replaced. The processor should rarely fail and should
be replaced only as a last resort. Processor modules can be
ordered from Service.

Logic Board Battery

The battery on the logic board controls the stored system settings,
such as date and time. It is important to note that the battery does
not affect power at startup.

The battery should be replaced if the system loses date and time
settings.

The iMac uses a lithium battery that must be disposed of in

Note:

accordance with hazardous waste regulations.

Troubleshooting General/ HFS Plus Formatted Drives - 15

HFS Plus Formatted Drives

The hard drive in the iMac is formatted with HFS Plus (also
referred to as Mac OS Extended format). It is important to note
that Norton Utilities version 3.5 is not compatible with HFS Plus
(or Mac OS Extended format), and in fact, can destroy data on the
hard drive.

Norton Utilities version 3.5.3 or 3.5.2 will not attempt to repair
a drive formatted with Mac OS Extended format and versions 3.5.1
and earlier cannot recognize that a hard drive is in Mac OS
Extended format and can result in hard drive corruption and loss
of all data on the drive.

When diagnosing hard drive problems, it is important to

Note:

verify whether or not the customer may have used the wrong disk
repair software for their drive before assuming that the problem
is hardware related.

If you experience problems with a hard drive that has been
formatted with HFS+, Apple Computer recommends using Disk
First Aid 8.2 (which is included on the system software CD that
ships with the iMac). Disk First Aid 8.2 can be used to recover
data that may have been deleted by Norton Utilities. (See the
Symantec Web site at http://www.symantec.com/nu/num­hfs.html for more information on Norton Utilities and Mac OS
Extended format.)

Some other disk utility and disk locking programs are
incompatible with Mac OS Extended format. Before you attempt to
use a disk utility or disk locking program, make sure the version
you have is compatible with Mac OS Extended format. Check the
documentation that came with the program or contact the
manufacturer or the vendor that supplied the program.

Use the Get Info command in System 8.1 to determine how a hard
drive has been formatted. Drives formatted with HFS will appear
as “Mac OS Standard”, while drives formatted with HFS+ will
appear as “Mac OS Extended.”

For more information on HFS Plus formatting of hard drives,
refer to the Technical Info Library, article # 30344.

Troubleshooting General/ Testing the Modem - 16

Testing the Modem

The iMac ships with ClarisWorks (a.k.a. AppleWorks) software,
which can be used to test the iMac modem connection. You should
run this test if the modem is not able to dial out. To perform this
test:

1. Locate and launch ClarisWorks. (Version 5.0 ships with the
iMac computer.)

2. From the ClarisWorks New Document window, select
Communications and click OK. You will be presented with an
untitled communications document.

3. Click on the settings menu item and select Connection from the
menu, which will bring up a new window. This window allows
you to select the communications toolbox device to access the
modem.

4. Click and hold the menu next to Method and select the Serial
Toolfrom the options presented.

5. Click on the Internal Modem setting under the Current
Portsetting. After selecting the port, click the OK button. (You
can ignore the rest of the settings.)

6. Open the serial port by selecting Open Connection from the
Session menu.

7. Type “AT” into the Communications document. The
modemshould respond with an OK message.

This procedure verifies that the program is connecting with the
modem and that the modem is responding.

A good test to see if the phone line is working is to type “ATDT”,
which will open the phone line. If the modem reports NO
DIALTONE, there isn't a valid analog line connected. If the phone
line works, you will hear a dial tone until you press the Return
key, at which time the modem will report NO CARRIER. A No
Carrier message means the phone line was successfully opened.

Other things that can be done here are:

• Call another modem to verify connections.

• Call a working phone number to see if you can successful

connect to an outside line.

• Use the ATI1-17 commands to check firmware versions and

modem features.

• Use ATZ to reset the modem back to its original configuration.

Troubleshooting Symptom Charts/ How to Use the Symptom Charts - 17

Symptom Charts

How to Use the Symptom Charts

The Symptom Charts included in this chapter will help you
diagnose specific symptoms related to the Power Macintosh G3/
Macintosh Server G3 (Blue and White) product. Because cures are
listed on the charts in the order of most likely solution, try the
cures in the order presented. Verify whether or not the product
continues to exhibit the symptom. If the symptom persists, try
the next cure.
original module before you proceed to the next cure.

For additional assistance, contact Apple Technical Support.

No Power

If you have replaced a module, reinstall the

Note:

No power. System is
completely dead. No
LED, no fan, no hard
drive power, and the
screen is completely
black.

1 Refer to “Testing for Power” mentioned earlier in this

chapter.

2 Verify the power outlet is good. Try a known-good power cord

to determine if the existing power cord could be the problem.

3 Possible bad USB keyboard. Verify the keyboard cable is

connected properly to the computer.Disconnect the keyboard
and power on the system via the button on the front of the
computer. Do you have power to the system now?

Yes

: The keyboard is bad. Replace the keyboard.

No

: Go to next step.

4 Reset the CUDA chip and try again. If the problem persists,

reset the logic board. (See “The CUDA Chip” and “Restarting
the Logic Board” earlier in this chapter for instructions.) Do
you have power to the system now?

Yes

: Run diagnostics.

No

: Go to next step.

5 Possible bad logic board or power/headphone board. Check for

trickle power on the logic board. Is there +5V power?

Yes

: Replace the logic board. If problem persists, replace the

power/headphone board.

No

: Check for trickle power at the power supply to power filter

cable. Is there +5V power?

-

: Replace the logic board. If problem persists,

Yes

replace the power filter board.

-

: Go to next step.

No

6 Possible bad power supply to power filter board cable. Check

for trickle power at the power supply board. Is there +5V
power?

Troubleshooting Symptom Charts/ Video Problems - 1 8

Yes

: Replace the power supply to power filter cable.

No

: Go to next step.

7 Possible bad power supply board. Replace the power supply

board.

Video Problems

No video, the screen is
either completely
black, or you will see
horizontal rolling
lines. There will be
power to the system,
however, which is
evidenced by an
illuminated amber
LED, and a running
fan.

1. Reset parameter RAM. Hold down <Command> <Option> <P> <R>
during startup but before “Welcome to Macintosh” appears.

2 Reset the CUDA chip and try again. If the problem persists,

reset the logic board. (See “The CUDA Chip” and “Resetting
the Logic Board” earlier in this chapter for instructions.)

3 Do you hear a normal boot chime at startup?

Yes: Go to next step.
No: Follow these steps to resolve the problem:

1. Reseat the SDRAM.

2. Reseat the processor module.

3. Replace the processor module.

4. Replace the logic board.

4 Verify that the following cables are attached securely:

• Internal RGB cable that attaches to the A/V interconnect
board at J5.

• Internal video cable that attaches to the logic board at J16
and the A/V interconnect board at J2.

• Internal RGB cable that attaches to the video portion of the
analog/video board at board at P301.

5 Replace the analog/video board. Exchange like-for-like,

there are two versions of the board.

6 Replace the internal video cable that attaches to the logic

board at J16 and the A/V interconnect board at J2.
7 Replace the A/V interconnect board.
8 Replace the logic board.
9 Replace the internal RGB cable that connects at the A/V

interconnect board at J5 and the analog/video board at P301.
10 Replace the CRT.