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 LHR Module Instructions” included with the replacement display/analog assembly 
(service module) and also discussed later in this chapter.
 Note:  The LHR coil (line conditioning module) is used in some international countries. Refer to the Take 
Apart chapter, LHR topic, for take-apart information.
2.Important: If you are returning a defective display/analog assembly, it is imperative that proper 
packaging guidelines be followed. The packing procedure is included with the replacement assembly. 
Incorrect packaging can result in damaged eMac displays. Please read and follow the directions 
enclosed in the shipping box of the new display prior to packaging the defective module.Failure to 
package the defective module according to the instructions may result in liability for the cost of the 
damaged display. 
3.Important: Do NOT lift, handle, bump, or manipulate the CRT neck/neck board on the Display/Analog 
assembly. Modules damaged by mishandling are NOT covered by Apple Warranty. Apple Authorized 
Service Providers can be liable for broken CRT necks due to improper handling. Refer to “CRT Neck/
Display/Analog Assembly Handling Information” topic in this chapter for more information.
4. The eMac display/analog assembly requires no voltage calibration or geometry adjustment. Should the 
display appear to require adjustment (focus, color, or brightness) use the “Displays” pane under System 
Preferences if using Mac OS X. If using Mac OS 9, use the Monitor Control Panel. If you can not make 
satisfactory corrections with these tools, replace the display/analog assembly.
5.Important: The microprocessor uses a heatsink/thermal pipe to transfer heat away. Whenever the 
heatsink is removed, the bottom side of the heatsink and the top of the microprocessor must be cleaned 
and thermal paste must be applied to the microprocessor. If the mating surfaces are not cleaned and 
thermal paste is not applied, the CPU may overheat and become damaged. Refer to “Thermal Paste 
Application” in this chapter.
6. The hard drive may have up to three thermal pads; two on the top and one along the side of the drive. 
The two pads on top may be discarded if you are replacing the drive; however, if the pad along the side 
of the drive appears damaged, replace it.
7. The eMac has an optional stand. Refer to the Upgrades chapter or the CIP procedures for instructions 
on how to install the stand.  
						

							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 A/C power cord; power cords from older iMac models may not fit into the A/
C socket. 
						

							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 and touching the circuitry on the logic board can cause the 
PMU to crash. If the PMU crashes, the battery life goes from about five years to about two days if 
the PMU is not reset. Refer to the next topic, “Resetting the PMU on the Logic Board” for the 
procedure. 
Many system problems can be resolved by resetting the PMU chip. The PMU reset button is 
located behind the user access door, refer to the graphic below. 
                                                 Location of the PMU Reset Button  
						

							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 user access door. 
						

							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 
finished the procedure and closed the computer.  
						

							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 9 booting systems) or Apple Service Diagnostics (for Mac OS X 
booting systems) and return the computer to the customer.
Note: This entire procedure resets the computer’s PRAM. Be sure to reset the computer’s time, 
date and other system parameter settings before returning the computer to the customer.