Symptom Charts
The symptom charts included in this lesson will help you diagnose specific symptoms related to the product. Because cures are listed on the charts in the order of most likely solution to least likely, 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.
NOTE
If a cure instructs you to replace a module and the symptom persists with the new module, reinstall the original module before you proceed to the next cure.
Apple Hardware Test
Apple Hardware Test (AHT) is a diagnostic tool for detecting issues with Apple internal hardware components such as the logic board, memory, modem, video RAM, and AirPort Card. The software does not check externally connected hardware components such as USB or FireWire devices, nor does it check non-Apple devices.
You can download the most recent AHT software from the AppleCare Service Source.
NOTE
“Symptom charts” is the term Apple uses to describe the following detailed lists of behaviors and cures. You will also find symptom charts in the service manuals.
Error Codes
If AHT detects an issue with a computer, it displays an error code, which is defined in the product's error code list. Consult the list for appropriate repair procedures associated with the code.
All error code lists are included in Knowledge Base document 112125, “Service Diagnostics Matrix.” You can also access this matrix by clicking the Diagnostic Software link on the Service Source home page.
Resetting the PMU on the Logic Board
Resetting the Power Management Unit (PMU) 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 off the computer by choosing Shut Down from the Special menu (if using Mac OS 9); if using Mac OS X, choose Shut Down from the Apple menu. |
3. | Remove the user access door. |
4. | Unplug all cables, except the power cord, from the computer. |
5. | Touch a metal surface inside the computer, and then unplug the power cord. This helps protect the computer from damage caused by electrostatic discharge (ESD). NOTE To avoid ESD, 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. |
6. | |
7. | Wait 10 seconds before connecting the power cord and powering on the computer. 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 “No Power” section elsewhere in this lesson. |
8. | Run MacTest Pro (Mac OS 9) or Apple Service Diagnostics (Mac OS X) and return the computer to the customer. |
NOTE
Warning: Resetting the power manager will permanently remove a RAM disk, if present, and all of its contents. You will also need to reset the settings in Date & Time preferences.
Power-On Self Test
There is a power-on self test (POST) that resides in the ROM of the eMac. This test runs automatically whenever the eMac is powered on after being fully shut down (not a restart).
If the test detects a problem, you will not hear a normal startup chime. Instead, the system will beep as explained below. Refer to “Error Beeps,” later in this lesson, for instructions on how to troubleshoot and repair an eMac that sounds error beeps at startup time.
Following is a list of what the error beeps at startup time signify:
One beep: No RAM is installed or detected.
Two beeps: Incompatible memory is installed. (The slots accept standard PC100 or PC133, 168-pin dual inline memory modules [DIMMs].)
Three beeps: No RAM banks passed memory testing.
Four or five beeps: Bad checksum for the remainder of the boot ROM. The ROM is bad.