Apple power mac g5 User Manual

Power Mac G5 Troubleshooting 177

Power-On Self Test: RAM and Processor Verification
A power-on self test in the computer’s ROM automatically runs whenever the computer is started 
up after being fully shut down (the test does not run if the computer is only restarted). If the test 
detects a problem, the status LED located above the power button on the front of the computer 
will flash in the following ways*:
1 Flash: No RAM is installed or detected.
2 Flashes: Incompatible RAM types are installed.
3...

178 Power Mac G5 Troubleshooting

Shut down the computer.
Disconnect the installed front panel board cable from the logic board.
Connect the front panel board cable from the troubleshooting tool to the logic board.
Try to start up the computer by pressing the power button on the troubleshooting tool.
Then proceed with the front panel board troubleshooting steps as described in the “Symptom 
Charts” in this chapter.
Power Supply Verification
To power on, the computer’s logic board requires a “trickle”...

Power Mac G5 Troubleshooting 179

Plug a known good power cord into the computer. Do not turn on the computer.
On the power supply cable connector: connect the black lead of the volt meter to pin 23 and 
connect the red lead of the volt meter to pin 1.
Note: This is a bottom view of the connector when it is unplugged and facing up.
The volt meter should measure approximately +5V. If you do not get a reading of +5V, recheck 
the volt meter connections and measure the voltage again. If the voltage is...

180 Power Mac G5 Troubleshooting

Power Supply P2 Connector
Pin#SignalColorPin#SignalColor
1+3.3VOrange9+5VRed
2+3.3VOrange10+5VRed
3+3.3VOrange11+5VRed
4+3.3VOrange12+12V3Yellow
5Reserve13+12V3Yellow
6+12VfanYellow14+12V1Yellow
7+12Vfan(12V2)Yellow15+12V1Yellow
8+25VWhite16RTNfan(GND)Black
Power Supply P3 Connector
Pin#SignalColorPin#SignalColor
1+5VRed5+5VRed
2GNDBlack6GNDBlack
3GNDBlack7GNDBlack
412V2Yellow8+12V2Yellow
Front Inlet Fan Connector
Pin#Signal
1FAN CPU Cpu AF MOTOR
2FAN CPU AF TACH
3FAN...

Power Mac G5 Troubleshooting 181

Front Panel Board Connector
Pin#SignalType
125V 
2V-GND 
3FW TPATwisted Pair Shield 110 
Ohm
4FW TPA +Twisted Pair Shield 110 
Ohm
5CHASSIS GND FW
6CHASSIS GND USB 
7FW TPBTwisted Pair Shield 
100 Ohm
8FW TPB+Twisted Pair Shield 
100 Ohm
9USB PWR 
10USB GND 
11USB Twisted Pair Shield 60 
Ohm
12USB+Twisted Pair Shield 60 
Ohm
13LED 
14PWR BTN 
15AUDIO SENSE 
16AUDIO COMTwisted TRI
17AUDIO RIGHTTwisted TRI
18AUDIO LEFTTwisted TRI 

182 Power Mac G5 Troubleshooting
Optical and Serial ATA Hard Drive Cable Connectors 
PowerOpticalSP1 
(HD1)
SP2 
(HD2)
Pin#ColorPin#ColorPin#ColorPin#Color
1BLK4BLK
2BLK3BLK
3BLK1BLK
4BLK2BLK2BLK
5BLK3BLK3BLK
6BLK1BLK1BLK
7BLK4BLK4BLK
Media Bay Temperature Sensor Cable
7 Pin ConnectorSignal 5 Pin Connector4 Pin Connector
13.3V11
2[ ]G B CLK2
3] [G B DAT2
4GND42
5OVER TEMP5
6DOOR AJAR 13
73.3V SLEEP4 

Power Mac G5 Troubleshooting  183

Symptom Charts
How to Use the Symptom Charts
The Symptom Charts included in this chapter will help you diagnose specific symptoms related 
to the product. Because cures are listed on the charts in the order of most likely solution, 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, reinstall the original module before...

184  Power Mac G5 Troubleshooting

Note: The following symptoms and cures apply to Power Mac G5 computers in this manual 
except the Power Mac G5 (June 2004 Dual 2.5 GHz/Early 2005 2.7 GHz) computers. For startup 
failures for these models, see “Startup Failures for Power Mac G5 (Dual 2.5 GHz/Early 2005 2.7 
GHz)” later in this section.
Power-on LED does not illuminate when power button is pressed, fans do not 
spin, and there is no boot tone or video
Verify power outlet is good.
Replace power cord....

Power Mac G5 Troubleshooting  185

Power Mac G5 (June 2004): Power-on LED illuminates when pressed in, but goes 
out when button is released, fans spin, and there is no boot tone or vid\
eo
Verify that the processors are properly seated.
Verify that the processors’ mounting screws are properly tightened. 
Remove the processors and check for damage to the logic board under the processors. If you 
see damage (see example below), replace the logic board. 
 
Note: For the Power Mac G5 (June 2004 Dual 2.0...

186  Power Mac G5 Troubleshooting

Power-on LED illuminates when power button is pressed but fans do not spin (\
or 
spin only momentarily) and there is no boot tone or video
Reseat video card. (Make sure video card is fully inserted in connector and end of card is 
secured by the connector latch.)
Reset logic board. Refer to “Resetting the PMU on the Logic Board” in this chapter.
Verify power supply cables are fully connected. 
Note: For the Power Mac G5 (June 2004 Dual 2.0 GHz) and Power Mac G5 (Early...