Hey Robo,
This is the diagnostic from the service manual:
"Computer begins to
power up, the fan and
hard drive are
spinning, the power
LED is lit, but there
is no startup chime or
video
1 Reset the logic board.
• Power Mac G4 (AGP Graphics): Refer to “Resetting the
PMU on the Logic Board” in this chapter.
• Power Macintosh G4 (PCI Graphics): Refer to “Resetting
the PCI Logic Board” in this chapter.
2 Power Macintosh G4 (PCI Graphics): Check the jumper block
at J25. Make sure the jumper is the correct color for the
processor type, includes all required inner metal clips, and
is installed in the correct direction. See “Processor Module”
in Take Apart for more information.
3 Reseat the processor module.
4 Verify all PCI and AGP cards are seated properly.
5 Replace the processor module.
6 Replace the logic board."
and resetting CUDA and Logic Board:
"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 “Resetting the PCI Logic Board” in this
chapter."
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.
Troubleshooting General/ Logic Board Troubleshooting - 17
Note:
This procedure resets the computer’s PRAM. Be sure to
check the computer’s 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).
Troubleshooting General/ Logic Board Troubleshooting - 18
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
Troubleshooting General/ Logic Board Troubleshooting - 19
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."
Wow never knew about the diagnostic LEDs on the PCI! I've got some here I have to take a look.
Richard
Message was edited by: spudnuty
