Apple eMac User Manual

© 2002 Apple Computer, Inc. All rights reserved.
 Service Source
Troubleshooting
eMac 

eMac  Troubleshooting - 1
 General Information
General Information
What’s New
1.Important:  The display/analog assembly contains a non-switching power supply preset at a 220V 
configuration. If you are replacing the display/analog assembly (service module), the voltage selection 
needs to be manually set (on the module) by way of a voltage jumper. This means if you are operating 
the computer in a 110V environment, you will have to install the voltage jumper. Refer to “Display/Analog 
Voltage Setting and...

2 - eMac  Troubleshooting
 General Information 8. The computer has a Power PC G4 microprocessor, running at a clock speed of 700 MHz.
9. The computer comes with 128 MB of SDRAM installed. Two DIMM slots support up to 1 GB using 128 
MB, 256 MB, or 512 MB DIMMs. The SDRAM modules are PC-100, 168-pin DIMMs.
10. The computer comes with either tray-loading CD-ROM or DVD-ROM/CD-RW (combo drive).
11. The 56K fax modem is only available on the DVD-ROM/CD-RW (combo drive) model. 
12. The eMac uses a different...

eMac  Troubleshooting - 3
 General Information
Logic Board, Top
PMU Reset Button Battery Hard Drive ConnectorSDRAM
Slots
VGA Output Port
Ethernet Port
Internal Modem Port
(Not Shown)
FireWire Ports
USB Ports
Sound Input
Port
Sound Output
Port 

4 - eMac  Troubleshooting
 General Information
Logic Board, Bottom
G4 Microprocessor
Video Processor
Blind Mate Connector Blind Mate Connector
AirPort Slot 

eMac  Troubleshooting - 5
 General Information
I/O Ports 

6 - eMac  Troubleshooting
 General Information
The PMU Chip
The PMU (Power Management Unit) is a micro controller chip that controls all power functions 
for the computer. The PMU is a computer within a computer. It has memory, software, 
firmware, I/O, two crystals, and a CPU. Its function is to: 
•Tell the computer to turn on, turn off, sleep, wake, idle, etc.
•Manage system resets from various commands.
•Maintain parameter RAM (PRAM).
•Manage the real-time clock.
Important: The PMU is very sensitive...

eMac  Troubleshooting - 7
 General Information
Resetting the PMU on the Logic Board
Resetting the PMU (Power Management Unit) on the logic board can resolve many system 
problems. Whenever you have a unit that fails to power up, you should follow this procedure 
before replacing any modules. 
1. Save open documents and quit all open applications. 
2. Turn the computer off by choosing Shut Down from the Special menu (if using Mac OS 9), or choose 
Shut Down from the Apple menu if using OS X.
3. Remove the...

8 - eMac  Troubleshooting
 General Information
4Unplug all cables, except the power cord, from the computer.
5Touch a metal surface inside the computer. Then unplug the power cord.This helps protect the 
computer from damage caused by electrostatic discharge. Important:
 To avoid electrostatic 
discharge, always ground yourself by touching metal before you touch any parts or install components 
inside the computer. To avoid generating static electricity, do not walk around the room until you have...

eMac  Troubleshooting - 9
 General Information
6 Press the PMU reset button (shown below) once and then proceed to step 7. Do NOT press the 
PMU reset button a second time because it could crash the PMU chip.
7 WAIT ten seconds before connecting the power cord and powering the computer on. If the 
computer powers on, go to the next step. If the computer does not power on, there is something 
else wrong with the computer, refer to the symptom/cure, “No Power” in this chapter.
8 Run MacTest Pro (for Mac OS...