Apple power mac g4 digital audio User Manual

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 3 
Note: 
 This entire procedure resets the computerÕs PRAM. Be sure 
to reset the computerÕs time, date, and other system parameter 
settings before returning the computer to the customer. 
Logic Board LEDs: Power Mac G4 (all models except PCI 
Graphics) 
There is one red LED on the Power Mac G4 (AGP Graphics/Gigabit 
Ethernet/Digital Audio/QuickSilver/QuickSilver 2002) logic 
boards. It indicates that there is power to the board and does not 
imply a fault condition. Hardware such as DIMMs and PCI cards 
should not be installed or removed when the LED is on. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 4 
Power Macintosh G4 (PCI Graphics) 
Processor Module 
The logic board comes with a removable processor module. The 
processor should rarely fail and should be replaced only as a last 
resort. Processor modules can be ordered from Service.
Note that when you replace the logic board on a Power Macintosh 
G4 (PCI Graphics), you must also change the processor jumper 
block and warranty sticker to be compatible with the processor 
module. Failure to install the jumper block properly will result 
in a unit that does not boot up. No jumper block is required for 
Power Mac G4 (AGP Graphics/Gigabit Ethernet/Digital Audio) 
processors.
Refer to ÒProcessor ModuleÓ in the Take Apart chapter for more 
information. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 5 
Resetting the Cuda Chip: Power Macintosh G4 (PCI 
Graphics) 
The Cuda is a microcontroller chip on the Power Macintosh G4 
(PCI Graphics) logic board. Its function is to 
¥ Turn system power on and off.
¥ Manage system resets from various commands.
¥ Maintain parameter RAM (PRAM).
¥ Manage the real-time clock.
Many system problems can be resolved by resetting the Cuda chip 
(see the Symptom Charts for examples). Press the Cuda reset 
button on the logic board to reset the Cuda chip. The Cuda reset 
button is located on the logic board to the right of the battery. 
Refer to the Logic Board Diagram earlier in this chapter for 
location information. If you continue to experience system 
problems, refer to ÒResetting the PCI Logic BoardÓ in this 
chapter. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 6 
Resetting the PCI Logic Board 
Resetting the logic board can resolve many system problems (see 
the Symptom/Cure tables for examples). Whenever you have a 
Power Macintosh G4 (PCI Graphics) computer that fails to power 
up, you should follow this procedure before replacing any 
modules. 
1. Unplug the computer.
2. Press the Power On button on the front of the unit.
3 . Open the side access panel.
4. Remove the battery from the logic board.
5. Wait at least 10 minutes before replacing the battery. 
6. Make sure the battery is installed in the correct +/- 
direction.
7 . Reassemble the computer and test the unit. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 7 
Note: 
 This procedure resets the computerÕs PRAM. Be sure to 
check the computerÕs time/date and other system parameter 
settings afterwards. 
Logic Board LEDs: Power Macintosh G4 (PCI Graphics) 
There are seven diagnostic LEDs on the Power Mac G4 (PCI 
Graphics) logic board. A graphic follows showing their location.  
DS1 = ATA drive activity 
If a CD and/or Zip are attached to the ATA bus, this LED will 
illuminate at power/on restart time for a few seconds. After that, 
it is unlikely it will illuminate again in a trouble-free system. If 
this light stays on for a prolonged period, this is a sign of trouble 
on the ATA bus. If devices are connected to the ATA bus and this LED 
is dark at boot time, that is also likely a sign of trouble. If a hard 
disk drive is attached to this bus, the LED flickers regularly 
indicating drive activity (reads/writes).  
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 8 
DS4 and DS5 = USB power for downstream devices 
DS5 = USB port 1- lower
DS4 = USB port 2- upper
(There is no DS2 or DS3 on the board.)
When illuminated, these LEDs indicate that the computer is 
providing power (+5 V) to downstream USB ports. USB devices do 
not need to be connected in order for these LEDs to illuminate. 
However, if one or both of the LEDs is not illuminated and a USB 
device is/was attached (and the system has completed its boot 
process), then the logic board has removed downstream power 
because of a trouble condition.
Since the downstream power is controlled individually for each 
port, it is possible to have these LEDs in a different state: one off 
and one on. This way if one port has troubled USB devices, the  
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   1 9 
other port can still be functional. These LEDs are not immediately 
illuminated at the beginning of a restart or cold power-on. During 
a successful/normal boot, the sequence will look like:
1. Unit is powered on and other LEDs will illuminate while DS4 
and DS5 are off.
2 . Then DS4 and DS5 on for a second or two
3. Then off very briefly (1 second)
4. Then back on (confirms secondary PCI bus is initialized and 
power now available)
These two LEDs are often useful when troubleshooting an 
unpredictable system. If they stay on (step 4) then the secondary 
PCI bus has been initialized which happens relatively late in the 
boot/hardware initializing process. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   2 0 
DS6 = Ultra ATA bus activity 
DS6 indicates Ultra ATA bus activity. 
DS7 & DS8 = Power Indication 
In a working unit, these LEDs should be in sync with each other: 
both on or both off. If one LED is on and the other is off, there is a 
problem.  
DS9 = CPU Bus Request 
When illuminated, this LED indicates that the CPU is requesting 
the bus. This LED will rarely glow as brightly as the others (like 
the Ultra ATA LED) given that the CPU is not always requesting the 
bus, and when it does, the period of time is short. As a result, you 
may need to watch this LED much more carefully than the others to 
tell if there is activity. If this LED is ever on continuously and 
bright, then the system is troubled and likely hung. 
						

							 
 TroubleshootingGeneral/Logic Board Troubleshooting  -   2 1 
Power Macintosh G4 (PCI Graphics) LEDs Locator
DS5
DS9
DS8
DS7
DS6
DS1DS4 
						

							 
 TroubleshootingGeneral/Power Supply Verification  -   2 2 
Power Supply VeriÞcation 
To start up, the Power Mac G4 logic board requires a ÒtrickleÓ 
power of +5V for AGP and PCI models, +28V for Gigabit Ethernet/
Digital Audio models, or +25V for QuickSilver models. If the 
system fails to start up, follow the procedure outlined below to 
determine whether the problem is related to the power supply. 
Note: 
 To verify the power supply, you need a volt meter. 
VeriÞcation Procedure 
Follow the procedures in the Take Apart chapter to access the 
power supply. 
Important: 
  For this verification procedure when connecting the 
volt meter leads to specific pins, ensure the power supply cable 
remains securely plugged into the power supply connector on the 
logic board.