Symptom Charts

The symptom charts included in this lesson will help you diagnose specific symptoms by following the guidelines set forth in the Apple General Trouble shooting Flowchart. 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.

No Power

The iMac G5 will not turn on. The display has no picture or color and no sounds can be heard coming from the fan or hard drive.

1.	Verify that the power outlet is good. Plug a different device into the socket to ensure there is power, or plug the iMac G5 into another outlet.
2.	Try a known-good power cord.
3.	Check the connection of the power cord on both ends. Verify that the plug is securely plugged into both the AC outlet and back of the computer.
4.	Remove the keyboard, mouse, and other peripherals such as speakers.
5.	Remove the back cover to access the diagnostic LEDs on the main logic board. Refer to “Diagnostic LEDs,” earlier in this lesson, for complete instructions on this procedure.
6.	Locate LEDs 1 through 4 above the large white arrow on the main logic board.
7.	Plug the power cord into the iMac G5 and into the AC outlet. Is LED 1 on or off? On: This indicates that the power supply is getting good power from the AC outlet. Go to step 8. Off: This indicates that your power supply should be replaced. Order and install the power supply for your computer.
8.	Turn on the computer by using the internal power button. With your finger, or with the nylon probe tool, press the small, metal button. Does the computer start up normally after pressing the internal power button? Yes: Press and hold the power button until the computer powers off. Unplug the power cord from the iMac and reinstall the back cover. Return the computer to the upright position. Plug the computer back in and press the power button to turn on the computer. Make sure the computer is starting up properly. If the computer will start up from only the internal power but will not power on from the power button on the back cover, the power button on the back cover may be faulty. Go to step 12. No: Press the SMU reset button, located below the internal power button.
9.	After pressing the SMU button, press the internal power button again. Does the computer start up normally now? Yes: Press and hold the power button until the machine powers off. Unplug the power cord from the iMac and replace the back cover. Return the computer to the upright position. Plug in the computer and press the power button to turn on the computer. Make sure the computer is starting up properly. If the computer will start up from only the internal power but will not power on from the power button on the back cover, this may indicate that the power button on the back cover is faulty. Go to step 12. No: Go to the next step.
10.	Unplug the power from the iMac G5, and remove the internal hard drive and set it aside. Plug in the iMac G5, and using the internal power button as before, power on the iMac G5. Does the iMac G5 start up now? Yes: The hard drive needs to be replaced. No: Go to the next step.
11.	When pressing the internal power button to power on the computer, does LED 2 come on momentarily, or not at all? Momentarily: The main logic board has detected 12 V, but the power supply cannot maintain it. Your power supply needs to be replaced. Not at all: Your main logic board needs to be replaced.
12.	If the computer will start up from only the internal power but will not power on from the power button on the back cover, the back cover may need to be replaced. Unplug the computer and remove the back cover. With the back cover removed, plug the power cord back in. Touch and hold an insulated screwdriver to the two contact points shown in the following figure. Does your computer start up when holding your screwdriver to these two contact points? Yes: This shows that the power button switch is working correctly. The back cover should be replaced. No: This indicates that the power button switch is not working correctly. The main logic board should be replaced.

Video

No Video

The computer will turn on, but the display has no picture or color. The boot chime can be heard, and the fan and/or hard drive activity can be heard.

1.	Check if the computer is in sleep mode. Press the spacebar to wake the computer. Did the computer wake from sleep mode? Yes: Choose Sleep from the Apple menu and wake the computer again to test the settings. Check Energy Saver settings to see when the computer is supposed to enter sleep mode. No: Continue to the next step.
2.	Reset parameter random-access memory (PRAM). Hold down Command-Option-P-R during startup until you hear the startup sound twice. Do you see video on the computer's display? Yes: Problem resolved. Choose Restart from the Apple menu and make sure the computer operates normally. No: Continue to the next step.
3.	Remove the back cover of the computer (as explained in Lesson 18, “Upgrading an iMac G5”) to access the diagnostic LEDs on the main logic board.
4.	Locate the diagnostic LEDs 1 through 4 above the large white arrow on the main logic board.
5.	Plug the power cord into the iMac G5 and into a known-good AC outlet. LED 1 should light if the computer starts up properly. Does LED 2 light? Yes: Continue to the next step. No: Follow the “No Power” troubleshooting instructions, earlier in this chapter.
6.	Press the internal power button (the top button to the left of the diagnostic LEDs) to turn on the computer. When the computer starts up, LED 2 should light after you hear the startup chime, indicating the midplane is processing power correctly. Does LED 2 light? Yes: Continue to the next step. No: Press the SMU reset button to reset system and power management. If LED 2 remains off after resetting the SMU, replace the midplane and verify the repair.
7.	LED 3 should light last, indicating that the midplane and LCD assembly have communicated and the LCD is ready to receive video. Does LED 3 light? Yes: This indicates that the main logic board is working correctly to produce video. Continue to step 9. No: Continue to the next step.
8.	Press the SMU reset button. Does the LED 3 light? Yes: Press and hold the internal power button until the computer powers off. Start the computer again and confirm that LED 3 is lighting reliably. Continue to step 9. No: The midplane is faulty. Replace the midplane and verify the repair.
9.	Press the internal power button again until the computer powers off. Unplug the computer and reinstall the back cover. Return the computer to the upright position. Plug in the computer and start up the computer. Does the unit have video now? Yes: Restart the computer and make sure that it is operating normally. No: Continue to the next step.
10.	Determine if the symptom is a backlight issue or a signal issue. Turn the display at an angle and look at it closely. Is the display completely black or dim with the desktop and icons visible? Completely black: The LCD backlighting has failed, most likely because of a faulty inverter board. Replace the inverter board and verify the repair. Dim with desktop: If you can make out the desktop and icons but only dimly, the backlights are not being driven properly. Replace the inverter board and verify the repair. Dim without icons: If you can see that the screen lights are on but you cannot see a desktop or icons, or any other signal, the LCD is faulty. Replace the LCD and verify the repair.

Display Is Tinted Another Color

1.	Reset PRAM. Hold down Command-Option-P-R during startup until you hear the startup sound twice. Does the computer display video after successfully resetting the computer's PRAM? Yes: Problem resolved. Restart the computer from the Apple menu and make sure the computer is starting up properly. No: Continue to the next step.
2.	Check for external video. Connect an external monitor to the mini-VGA port. Do you have external video now? Yes: Replace the display/panel and go to step 3. No: Replace the main logic board.
3.	After replacing the display/bezel? Do you have video now? Yes: Problem solved. No: Replace the main logic board.

Hard Drive

In a hard drive failure, the computer fails to start up to the desktop and may display a fiashing question mark on top of a folder.

1.	Start up from the Apple Hardware Test (AHT) disc that came with the computer. Run the Quick/Extended test. Does the computer pass the AHT? Yes: Start up from the Install CD that came with the computer. Choose Open Disk Utility from the Installer menu. Select the hard drive, then click Repair Disk in the First Aid pane. Restart the computer. No: Replace the component that AHT indicates, then continue to the next step.
2.	Does the computer start up properly now? Yes: Problem resolved. No: Reinstall system software. Continue to the next step.
3.	Does the computer start up properly now? Yes: Problem resolved. No: Replace the hard drive.
4.	Does the computer work now? Yes: Problem resolved. No: Replace the main logic board.

System Hangs During Normal Startup Process

1.	Start up from the system CD that came with the computer and see if the hard drive mounts on the desktop.
2.	Using Disk Utility, erase the hard drive.
3.	Check all cable connections to and from the hard drive.
4.	Replace the hard drive.
5.	Replace the main logic board.

Optical Drive

CDs or DVDs Do Not Show Up on the Desktop

1.	Verify that Finder preferences are set correctly. Choose Preferences from the Finder menu, click General, then select the checkbox to show CDs, DVDs, and iPods on the desktop.
2.	Insert the Mac OS X Install Disc 1 that came with the computer. Does the install disc appear on the desktop? Yes: If some discs show up on the desktop, the drive is okay; the problem is the individual discs that don't appear. Try cleaning these discs, and make sure they are in a format that the computer can read. No: Continue to the next step.
3.	Leave the Mac OS X Install disc in the drive and choose Shut Down from the Apple menu.
4.	Once the computer has shut down, hold down Option and press the power button to access the Startup Manager. You will see a blue background, a circular arrow, and a right arrow; between them is a button with the name of your hard drive.
5.	Click the circular arrow to rescan the hardware, then wait about 30 seconds to see if another button comes up with the name “Mac OS X Install Disc 1.”
6.	Select the button with your hard drive's name, then click the right arrow to start up normally from that drive.
7.	Did a button for the Mac OS X Install Disc 1 ever appear in step 5? Yes: Create a new user. Log in using the new user account. If the disc appears on the desktop while logged in as the new user, there is a problem with the original user account. Move critical data to the new account and verify the repair. If the disc still does not appear on the desktop while logged in as the new user, there is a problem with the system software. Back up the information on the startup disk to a network or external device and reinstall the operating system. Verify the repair. No: Continue to the next step.
8.	Choose About This Mac from the Apple menu, then click More Info to launch System Profiler.
9.	Select ATA (listed under Hardware) in the Contents column on the left. The device tree on the right should show two items: the hard drive and the optical drive. Do you see two items on the device tree? Yes: Continue to the next step. No: Physically reseat the optical drive and check System Profiler again. If the optical drive appears, the problem has been resolved. If not, continue to the next step.
10.	Replace the optical drive.
11.	Replace the main logic board.

Computer Will Not Burn Discs

1.	Check whether the drive can read discs normally. Insert the Mac OS X Install disc that came with the computer. Does it appear on the desktop? Yes: Continue to the next step. No: Follow the instructions for “CDs or DVDs Do Not Show Up on the Desktop.”
2.	Which of these error messages do you see when you try to burn discs? Unknown Error -2147352480: Refer to Knowledge Base documents 25480, “Mac OS X: 'Unknown Error -2147352480' when burning CD-R, CD-RW, or DVD-R media,” and 25750, “You see a 'buffer underrun' error when burning a disc in Finder or iTunes.” Buffer underrun error: Refer to Knowledge Base documents 25480 and 25750. Unknown Error: Refer to Knowledge Base document 152224, “I got an 'unknown error' message while burning a CD or DVD disc.” None of these alert messages: Is the problematic disc drive inside the iMac, or is it an external device attached by a USB or FireWire cable? If internal, continue to step 3. If external, contact the manufacturer of the external drive.
3.	The iMac can mount discs, it just can't burn them. Try purchasing a different brand of discs and test whether these discs will burn. Sometimes certain discs won't burn, either because of poor quality or because they are damaged or old. Do the new discs burn correctly? Yes: Problem resolved. Use the new discs from now on. No: Continue to the next step.
4.	In the Finder, choose your startup disk and press Command-I to open the Info window. Does the drive have at least one gigabyte (1 GB) available? Yes: Continue to the next step. No: The computer needs a considerable amount of available disk space to prepare a disc for burning. Free up at least 1 gigabyte on the computer by deleting unneeded items and emptying the Trash. Try burning a disc again. Does it burn correctly now? If yes, problem resolved. If no, when you try to burn a disc, are you burning a disc from the Finder, from iTunes, or from a different application? Refer to Knowledge Base documents 151904, 150293, 151701, and 153426 for disc burning issues. Does it burn a disc now? If yes, problem resolved. If no, continue to next step.
5.	Reinstall the system software following the instructions in Knowledge Base document 151641, “Reinstalling Mac OS X.” Try burning a disc again. Did the disc burn correctly? Yes: Problem resolved. No: Replace the optical drive. Does it burn correctly now? If yes, problem resolved. If no, replace the main logic board.

Inserting Discs Issue

1.	Is there a disc already in the drive? Refer to Knowledge Base document 106752, “Macintosh: How to Eject a Disc When Other Options Do Not Work.”
2.	Choose About This Mac from the Apple menu, then click More Info to launch System Profiler.
3.	Select ATA (listed under Hardware) in the Contents column on the left. The device tree on the right should show two items: the hard drive and the optical drive. Do you see two items here? Yes: Continue to the next step. No: Physically reseat the optical drive and check System Profiler again. If the optical drive appears, the problem has been resolved. If not, continue to the next step.
4.	Replace the optical drive.
5.	Replace the main logic board.

Optical Disc Constantly Ejects

1.	Disconnect all peripheral devices, especially the mouse in cases where the disc is constantly ejecting.
2.	Try cleaning the disc. If it is dirty or scratched, it may not mount.
3.	Try a different disc.
4.	Boot from AHT (hold down the C key at startup) or boot from the system install disc (to use Startup Manager, hold down the Option key at startup).
5.	Perform a clean install of Mac OS X with the disc that came with the computer.
6.	Reseat the optical drive.
7.	Replace the optical drive.
8.	Replace the main logic board.

Fans

Loud Fan Noise

The grill on the bottom of the iMac G5 lets a trio of fans draw cool air into the system. Advanced thermal software spins the fans fast or slow as needed, passing the heated air through a slit on the back cover. As the system usage increases, the fans will adjust their speed to meet the cooling needs of the system.

Under normal conditions, rotating fans will make a slight hum that varies in relationship with their rotational speed and the amount of air that they are moving. In addition, the normal functioning of the hard drive and optical drive will generate additional whirring and scratching sounds that may be audible. All of these sounds are normal and do not indicate a failure with the computer.

To begin troubleshooting a possible fan issue, we need to qualify the sound that you're experiencing.

1.	Does the sound occur only under specific light/heavy usage conditions? Yes: CPU-intensive applications such as iTunes, Garage Band, DVD Player, etc., or two or more applications open at once will cause the fans to run at an increased rate, making them more noticeable. If the sound occurs only when one or more of these applications is running, this is normal. No: If the sound isn't affected by CPU-intensive applications, it may be due to other factors. Go on to the next step.
2.	Is the sound always present, or does the sound vary? Always present: The normal functioning of the hard drive and optical drive will generate additional whirring and scratching noises that may be audible. Let's see if this sound is related to one of the components. Go to step 4. Varies: Under normal conditions, rotating blowers will make a slight hum that varies in relationship with their rotational speed and the amount of air that they are moving. Let's see if this is indeed the case. Go to the next step.
3.	Are the fans making a normal humming sound that increases/decreases in relation to processor usage? As the fans increase their speed to cool the system, the sound level will increase. Launch Activity Monitor (/Applications/Utilities) to determine whether the noise corresponds with heavy usage of the CPU. Does fan activity vary with the CPU Usage graph in Activity Monitor? Yes: This is normal operation and none of your fans requires replacement. As the system CPU usage increases, the fans will adjust their speed using advanced thermal software to meet the cooling needs of the system. As the fans increase their speed to cool the system, the sound level will increase. No: If the fan activity does not coincide with CPU usage, the sound you're hearing may not be fan activity. Go to the next step.
4.	The normal functioning of the hard drive and optical drive will generate additional whirring and scratching noises that may be audible. We can isolate these noises by booting the computer with the iMac G5 Install Mac OS X Install Disc 1. Place the disc in the drive, and restart your computer, holding down the C key as the computer starts up. Once at the Installer window, choose Open Disk Utility from the Installer menu. Once Disk Utility is open, select your Macintosh HD, then click Unmount on the toolbar. Note: If you have multiple partitions, you should unmount each of these partitions. This will spin down the hard drive. The optical drive will also be busy at this time; wait a moment for the optical drive to spin down also and then listen to the machine. Is the sound that you've been experiencing still present? Yes: With the hard drive and optical drive inactive, all you should be hearing are the fans in the machine. While booted using the CD, these fans should be running at a lower level since the CPU is under very little task with both drives inactive. Fan sound that includes objectionable ticking, whistling, or squealing may require further investigation and/or replacement of the particular fan. Go on to the next step. No: The normal functioning of the hard drive and optical drive will generate additional whirring and scratching sounds that may be audible. All of these sounds are normal and do not indicate a failure with the machine. If you want to check the health of the hard drive, refer to Knowledge Base document 152349, “Replacing a disk before it fails.”
5.	Power off the computer, remove the power cord and any other cables that are connected to the computer and remove the back cover. Plug in the computer and start it up by pressing the internal power button. As the computer starts up, listen carefully to each of the fans, and see if you can locate one of the three fans which the objectionable ticking, whistling, or squealing sound is coming. Can you pinpoint the fan making the sound? Yes: If the sound is coming from one of the fans near the hard drive, you can order and install the Upper Fan kit for the computer. If the sound is coming from the fan near the power supply, order the Lower Fan kit. No: If you can hear an objectionable ticking, whistling, or squealing sound, but you cannot identify the source of the sound, contact Apple Technical Support.

Fans Run at a Constant High Speed

If the fans on the system are running at a constant high speed, or ramp very quickly to high speed and do not vary this speed once reached, the fans are most likely receiving incorrect thermal input. In these cases, follow these steps:

1.	Press the SMU reset button to reset system and power management, then test to see if the fans still exhibit the issue.
2.	Boot from the iMac G5 Install DVD or another iMac G5 of the same type in FireWire Target Disk Mode and see if the issue persists. If the fans run normally here, reinstall the system software. Be sure to give the system enough time to re-create the issue when booted to these other volumes.
3.	Verify that the hard drive sensor cable is plugged in correctly. If necessary, replace the hard drive sensor cable.
4.	Replace the hard drive (the hard drive includes the sensor on the hard drive carrier).
5.	Replace the main logic board.

AirPort

Computer Cannot Connect Wirelessly With AirPort

1.	Choose About This Mac from the Apple menu.
2.	Click More Info to launch System Profiler.
3.	In System Profiler, select AirPort Card under the Hardware heading.
4.	Does the section to the right say “No Information Found”? Yes: It looks like the computer doesn't realize it has an AirPort Extreme Card installed. Go to the next step. No: It looks like your iMac recognizes that it has an AirPort Extreme Card installed. Go to step 6.
5.	Remove the back cover and reseat the AirPort Extreme Card. Does System Profiler recognize the card? Yes: Problem resolved. No: Replace the AirPort Extreme Card.
6.	Remove the back cover. Reconnect the antenna cable to the AirPort Extreme Card. Press the antenna connector firmly, to make sure it's fully connected to the iMac. Replace the back cover and reconnect the power cord. Can you connect wirelessly? Yes: Problem solved. No: Refer to Knowledge Base document 106858, “AirPort troubleshooting guide.”
7.	Replace the AirPort Extreme Card.
8.	Replace the main logic board.

AirPort Signal Seems to Be Very Weak

If the AirPort antenna is not plugged in all the way, you may have very short AirPort range.

1.	Remove the back cover. Reconnect the antenna cable to the AirPort Extreme Card. Press the antenna connector firmly, to make sure it's fully connected to the iMac. Replace the back cover and reconnect the power cord. Did the reception improve? Yes: Problem solved. No: Refer to Knowledge Base document 106858, “AirPort troubleshooting guide.”
2.	Replace the AirPort Extreme Card.
3.	Replace the main logic board.

Speakers

Sound Does Not Come From the Speakers

1.	Press the volume up button on the keyboard (it has a speaker icon on it). Alternatively, follow the directions in Knowledge Base document 151838, “Adjusting your computer's sound volume.” Do you hear sound now? Yes: Problem resolved. The volume was muted. When this happens again, just press the volume up and down keys to regulate the volume. No: Are there any external microphones, speakers, or headphones plugged into the iMac? If yes, continue to step 2. If no, continue to step 3.
2.	Disconnect the external microphones, speakers, or headphones. Do you hear sound now? Yes: It looks like the built-in speakers are working properly. Now try plugging in a different set of speakers or headphones. Continue to step 4. No: Continue to step 3.
3.	Unplug any USB devices plugged into the computer, other than the Apple mouse and Apple keyboard. Do you hear sound now? Yes: You may have a USB audio device, such as a USB microphone adapter or USB speakers, plugged into the iMac. Contact the device's manufacturer to troubleshoot this issue. No: Reset PRAM, which stores settings for sound, and continue to step 5.
4.	With new speakers or headphones plugged in, do you have audio? Yes: The issue may be with the external microphone, speakers, or headphones that were plugged into the iMac originally. Work with the manufacturer to troubleshoot the speakers or headphones. No: There may be something wrong with the audio output port on the iMac. Replace the main logic board.
5.	After resetting the PRAM, do you hear sound now? Yes: Test the audio again. Make sure Sound preferences are set correctly. Problem resolved. No: Replace the main logic board.

Sound Comes Out of Only One Speaker

1.	Are there any external microphones, speakers, or headphones plugged into the iMac? Yes: Disconnect any external microphones, speakers, or headphones. Do you hear audio from both of the built-in speakers on the iMac? If no, continue to the next step. If yes, the built-in speakers are working properly. Thus there may be an issue with the microphone, speakers, or headphones that were plugged into the iMac. Contact the device's manufacturer to troubleshoot this issue. No: Continue to the next step.
2.	Choose System Preferences from the Apple menu.
3.	Open Sound preferences, then click Output.
4.	Check the speaker balance. If the balance setting is set to the left or right speaker, sound would come out of only one speaker. Make sure the balance setting is in the middle. After adjusting the audio balance, do you have audio from both speakers now? Yes: The balance was not set properly. Problem resolved. No: Replace the main logic board.

Mouse

Mouse Does Not Work at All

1.	Try using the mouse on another surface. Nonrefiective, opaque surfaces without repetitive patterns work best. The surface should be clean, but not shiny.
2.	Unplug any USB devices plugged into the computer, other than the Apple mouse and Apple keyboard.
3.	Try another known-good USB mouse.
4.	Replace the mouse.
5.	Replace the main logic board.

Mouse Works Intermittently (Cursor Freezes Randomly)

1.	Unplug any USB devices plugged into the computer, other than the Apple mouse and Apple keyboard.
2.	Reconnect the USB devices one by one, and test the mouse after each to determine which device is causing the issue. Once you have isolated the “problem child” that isn't playing well with others, contact the manufacturer of that device for suggestions or assistance.
3.	Try a known-good USB mouse.
4.	Replace the mouse.
5.	Replace the main logic board.

Mouse Is Slow to Respond

1.	Try using the mouse on another surface. Nonrefiective, opaque surfaces without repetitive patterns work best. The surface should be clean, but not shiny.
2.	Choose System Preferences from the Apple menu.
3.	Open Keyboard & Mouse preferences, then click Mouse.
4.	Drag the Tracking Speed slider to set how fast the pointer moves. Drag the Double-Click Speed slider to set how fast you have to double-click.
5.	If the mouse still doesn't work, insert the Mac OS X Install disc that came with the computer. Restart the computer, holding down the C key to start from the disc instead of the hard drive. Does the mouse work when the computer is started up from this disc?
6.	Try a known-good USB mouse.
7.	Replace the mouse.
8.	Replace the main logic board.

Keyboard

None of the Keys on the Keyboard Works

1.	Unplug all devices from the computer, including the mouse, keyboard, printer, scanner, external hard drives, and hubs. NOTE Warning: Some devices may require you to perform steps before it is safe to unplug them (for example, you must unmount external storage devices).
2.	Plug the keyboard firmly and securely into the back of the computer. Plug the mouse firmly and securely into the back of the computer. Take special care to make sure the connector is completely in the socket. Does the keyboard work now? Yes: Problem resolved. No: Unplug the keyboard and plug it into another USB slot on the back of the iMac. Continue to the next step.
3.	Does the keyboard work now? Yes: Replace the main logic board. No: Unplug the keyboard and plug the mouse into the port the keyboard just occupied. Continue to the next step.
4.	Does the mouse work now? Yes: Replace the keyboard. No: Replace the main logic board.

Certain Keys Do Not Work

1.	Unplug all devices from the computer, including the mouse, keyboard, printer, scanner, external hard drives, and hubs. NOTE Warning: Some devices may require you to perform steps before it is safe to unplug them (for example, you must unmount external storage devices).
2.	Plug the keyboard firmly and securely into the back of the computer. Plug the mouse firmly and securely into the back of the computer. Does the keyboard work now? Yes: Problem resolved. No: Unplug the keyboard and plug it into another USB slot on the back of the iMac. Continue to the next step.
3.	Does the keyboard work now? Yes: Replace the main logic board. No: Unplug the keyboard and plug the mouse into the port the keyboard just occupied. Continue to the next step.
4.	Does the mouse work now? Yes: Replace the keyboard. No: Replace the main logic board.

Keys Are Sticky or Slow to Respond

1.	Try a known-good keyboard.
2.	Choose System Preferences from the Apple menu.
3.	Open Keyboard & Mouse preferences.
4.	Adjust the “Key Repeat Speed” and “Delay Until Repeat” settings.
5.	Replace the keyboard.

When Using the Keyboard, Strange Characters Appear on the Screen

Depending on the iMac computer's settings, a simple keystroke can change the keyboard from English to Japanese. This can result in some bizarre characters showing up when you type. To switch to the U.S. keyboard:

1.	Choose System Preferences from the Apple menu.
2.	Open International preferences, then click Input Menu.
3.	Scroll down the list and uncheck any non-U.S. keyboard layouts.
4.	Close System Preferences. Try typing a few characters. Do the correct, English characters appear? Yes: Problem solved. No: Replace the keyboard.

USB Port on Keyboard Does Not Work

1.	Unplug all devices from the keyboard.
2.	Plug the Apple mouse into the left USB port on the keyboard. Does the mouse work when it's plugged into this port? Yes: Plug the mouse into the right port. Does it work? If yes, try a known-good keyboard. If no, try a known-good mouse to rule out the mouse. Continue to the next step. No: Try a different mouse or keyboard.
3.	Unplug the keyboard from the USB port on the back of the iMac, and plug the mouse into the port the keyboard just occupied. Does the mouse work now? Yes: Replace the keyboard. No: It appears that the USB port isn't functioning properly. Replace the main logic board.

Error Beeps

Computer Beeps at Startup

1.	Check that the memory modules are iMac G5–compliant. iMac G5 computers work with memory modules (DIMMs) that meet all of these criteria: PC3200, +2.5 V, unbuffered, 8-byte, nonparity, 184-pin, and 400 MHz DDR SDRAM. DIMMs with any of the following features are not supported in the iMac G5 computer: registers or buffers, PLLs, ECC, parity, or EDO RAM.
2.	Reseat the memory into the slot.
3.	Replace the memory.
4.	Replace the main logic board.

USB

A USB Device Does Not Work

1.

Unplug all of the USB devices from the iMac except the Apple keyboard and Apple mouse.

2.

Plug the malfunctioning USB device directly into the back of the iMac. Does it work as expected now? Yes: The device works when plugged directly into the computer. This indicates a conflict with one of the other USB devices. You can test by reconnecting the devices one by one and seeing where the issue occurs, then contacting the device's manufacturer for assistance. No: Unplug the device from the iMac and plug the keyboard into the port the device just occupied. Is the keyboard still working? If no, replace the main logic board. If yes, the Apple keyboard works when plugged into the USB port the device was plugged into. This points to an issue with the device. Review the documentation that came with the device. Install any necessary drivers and contact the device's manufacturer for assistance.

Dialog Says “Not Enough Power to Function”

Plug this device into the computer's USB port, rather than the keyboard USB port. Any USB device connected to the keyboard needs to be either a self-powered device (with its own AC power supply) or a low-power device (does not need a large amount of voltage to operate). The device may draw more power than the keyboard can provide.