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K Service Source

Power Macintosh G3
K Service Source

Hot Issues
Power Macintosh G3 Desktop
Hot Issues Introduction - 1

This chapter is designed to highlight unique or high-
priority product issues that you should be aware of before
servicing the Power Macintosh G3 Desktop computer.

This chapter alerts you to important issues and provides
links 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.
Hot Issues Shared Logic Board - 2

Shared Logic Board
The Power Macintosh G3 Desktop and Minitower computers
use the same logic board, but there are jumper settings that
differ between them (see "Jumper Location J28" and
"Jumper Location J16" in the Troubleshooting chapter).

Processor Module Vs. Card
Whereas previous Power Macintosh computers featured a
user-installable processor card, this logic board uses a
processor module that must not be removed by the customer
(see "Processor Module" in the Take-Apart chapter).
Hot Issues Power Supply Jumper - 3

Power Supply Jumper
The Power Macintosh G3 Desktop logic board has a power
supply jumper, which is installed at J28. The setting of this
jumper differs between the Power Mac G3 Desktop and
Minitower. Failure to install this jumper in the correct
position may result in a computer that won't boot up. (See
"Jumper Location J28" in the Troubleshooting chapter.)

Processor Module Jumper
The Power Macintosh G3 Desktop logic board has a processor
module jumper, which is installed at J16. The processor
jumper is color coded for the speed of processor module
used. Failure to install the correct jumper may result in a
computer that won't boot up. (See "Jumper Location J16"
in the Troubleshooting chapter.)
Hot Issues Warranty Sticker - 4

Warranty Sticker
There is a warranty sticker that covers the processor
module jumper. The customer's warranty is void if this
sticker is tampered with. Service Providers must replace
this sticker if they have removed it during servicing to
protect the customer's warranty. (See "Processor Module"
in the Take-Apart chapter.)

Power Supply Voltage Setting
There is a switch on the back of the power supply that
controls the voltage setting. The voltage switch must be set
correctly to avoid damaging the computer. (See "Voltage
Switch" in the Basics chapter for more information,
including an international voltage chart.)
Hot Issues Voltage Regulator - 5

Voltage Regulator
There is a removable voltage regulator on the logic board,
which comes with the logic board and can also be ordered as a
separate module. (See "Voltage Regulator" in the
Troubleshooting chapter.)

I/O Card
Some I/O functions on the logic board are handled through a
removable I/O card that must be installed for the computer
to operate properly. (See "I/O Cards" in the
Troubleshooting chapter.)
Hot Issues ROM DIMM - 6

The Power Macintosh G3 Desktop logic board uses a ROM
DIMM as opposed to soldered ROM. You should not remove the
ROM DIMM from the logic board. (See "Logic Board" in the
Take-Apart chapter for instructions on how to prepare the
logic board for return to Apple Computer.)

The Power Macintosh G3 Desktop uses SDRAM DIMMs.
DIMMs from older Macintosh computers, although they will
fit, are not compatible and should never be used in the Power
Macintosh G3 computers. (See "SDRAM DIMMs" in the
Basics chapter and refer to the Power Macintosh G3 Desktop
section of the Memory Guide.)
Hot Issues SGRAM Video Memory - 7

SGRAM Video Memory
Power Macintosh G3 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.)

EIDE Bus Issue
If you have only one device connected to the EIDE bus, the
device must be plugged into the first EIDE connector on the
logic board (the one closer to the rear panel), which is
marked J9. If you plug the device into J10 and leave J9
empty, the device may not boot up. (See "Connecting EIDE
Devices to the Logic Board" in the Basics chapter.)
Hot Issues Master/Slave Support - 8

Master/Slave Support
Some Power Macintosh G3 Desktop computers support
adding two ATA/IDE devices to the same ATA/IDE channel, or
what is commonly known as master and slave. This
configuration provides user with the ability to add additional
hard drives or removal media devices to their system.
Because the cabling is different, you cannot replace ATA
drives with SCSI drives and vice versa. (See "Support for
Master and Slave" in the Basics chapter.)

Ultra Wide SCSI Cable Routing
The Ultra Wide SCSI cable (if present) must be routed
inside the computer's chassis in a very specific manner.
Failure to route the cable correctly could result in
performance problems. (See "Ultra Wide SCSI PCI Card" in
Hot Issues DVD-ROM Disk Damage - 9

the Take-Apart chapter.)

DVD-ROM Disk Damage
The Power Macintosh G3 Desktop offers DVD-ROM drives as
a build-to-order option. It is important to note that DVD
disks are much more prone to damage than CD-ROM disks.
Any type of scratch or other abuse may result in a disk that
is unreadable. (See "DVD-ROM Drive Technology" in the
Basics chapter.)

CD-ROM Ejection Problem
If you have a CD-ROM drive in a Power Mac G3 Desktop that
fails to eject CDs properly, you may need to install poron
bumpers. (See "CD-ROM Drive" in Troubleshooting.)
Hot Issues HFS+ Formatted Drives - 10

HFS+ Formatted Drives
Hard drives that ship with the Version 2 Power Macintosh
G3 logic board (part number 661-2063) use a file format
called Mac OS Extended format, also referred to as HFS+.
Norton Utilities version 3.5 is not compatible with Mac OS
and version 3.5.1 and earlier can result in hard drive
corruption and loss of all data on the hard drive. If you
experience problems with a hard drive in one of these
systems, Apple Computer recommends using the version of
Disk First Aid included on the system software CD that
shipped with the unit. (See "HFS+ Formatted Drives" in the
Troubleshooting chapter.)
Hot Issues Power-On Issue - 11

Power-On Issue
If you experience a power-on issue with the Power
Macintosh G3 Desktop where the power supply fan is
spinning, but there is no boot tone, no hard drive noise, no
power LED, and no video, you may have an improperly
installed or faulty voltage regulator. You should always
reseat and/or replace the voltage regulator before replacing
the logic board. (See "System" symptom/cures in the
Troubleshooting chapter.)
K Service Source

Power Macintosh G3 Desktop
Basics Overview - 1

The Power Macintosh G3
desktop chassis design
allows you to access the logic
board and its components,
including the removable
processor, without having to
remove the power supply or
any drives. This flexible
design makes this computer
easy to service and upgrade.

The Power Macintosh G3
desktop has a unique PERCH
slot that accepts an I/O card
that provides audio
capabilities of the computer.
Basics Overview - 2

Features of the Power Mac G3 Desktop include: