Apple power mac g5 late 2005 User Manual

Power Mac G5 (Late 2005) Troubleshooting — General Information 141
Power Supply Verification
To power on, the computer’s logic board requires “trickle” power. If the system fails to power on, 
first reset the SMU (remove power cord for approximately two minutes). If the unit still doesn’t 
power on, follow the procedure outlined below to determine whether the issue is related to the 
power supply. 
Verify trickle power
Diagnostic LED 4 indicates the presence of trickle power required by the logic board...

Power Mac G5 (Late 2005) Troubleshooting — General Information 142
Location of Bus Bar Tabs and Terminals
Note: This is a top view of the main logic board with the processor module removed. You must 
test the voltages with the processor module installed. 
MLB Power Bus Bar
VoltagePositive LeadGround Lead
3.3 VTab 1Tab 4
5.1 VTab 2Tab 4
0 VTab 3Tab 4
0 VTab 4Tab 5
0 VTab 5Tab 4
0 VTab 6Tab 4
0 VTab 7Tab 4
12 VDCTab 8Tab 4
12 VDCTab 9Tab 4
NominalMinMax 
+3.3 VDC3.14 VDC3.48 VDC 
+5.1 VDC4.85 VDC5.35 VDC...

Power Mac G5 (Late 2005) Troubleshooting — General Information 143
CPU Terminals CPU A
VoltagePositive LeadGround Lead
12 VTerminal 1Terminal 2 
0 VTerminal 2Tab 4
NominalMinMax 
+12 VDC10.8 VDC13.2 VDC
 
CPU Terminals CPU B
VoltagePositive LeadGround Lead
12 VTerminal 1Terminal 2 
0 VTerminal 2Tab 4
NominalMinMax 
+12 VDC10.8 VDC13.2 VDC  

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 144
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...

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 145
Verify that processors’ mounting screws are properly tightened.
Reseat front panel board.
Test whether the front panel board or power button is at fault. Remove the installed front 
panel board and swap it for a known-good front panel board.
Replace front panel board.
Replace power button.
Replace power supply.
Replace logic board.
Power-on LED illuminates when pressed in, but goes out when button is released, 
there is no boot tone or video,...

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 14
Power-on LED illuminates when power button is pressed and fans spin 
continuously but 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.) For video cards that require power cables, check that they 
are connected.
Verify speaker cable is fully seated.
Reset logic board. Refer to “Resetting the Logic Board” in this chapter.
Check...

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 14
Power-on LED illuminates, fans and processor pump run harder, there is no boot 
and the system shuts down within a few minutes
Remove the processor and look for loss of fluid on the absorbent liner on top of the power 
supply. If you see drops of fluid, replace the processor, otherwise go on to the next step.
Reseat the processor. 
Replace the processor
Replace the logic board
Replace the power supply
Fluid leak is suspected and the...

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 14
Fans  
Individual fan failure
Replace fan 
Exception: The media blower located between the optical and hard drives cannot be 
replaced. You must replace the enclosure for this part.
Replace logic board
All fans run at high speed
Check for proper ventilation around the exterior of the computer.
Check that the clear plastic air deflector is in place.
Run Apple Service Diagnostic (refer to “Thermal Calibration” earlier in this chapter)....

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 14
Other Failures
Air deflector sensor 
Reseat air deflector sensor board cable
Replace air deflector sensor board
Replace logic board
Optical drive 
Replace optical drive cable
Replace optical drive
Replace logic board
FireWire port (front panel A) 
Reseat front panel board
Replace front panel board
Replace logic board
Firewire port (rear AB) 
Replace logic board
Firewire port (rear BB) 
Replace logic board
Internal speaker 
Check speaker...

Power Mac G5 (Late 2005) Troubleshooting — Symptom Charts 150
Combo Card 
Reseat antenna cables connected to Combo card
Replace Combo card
Replace antenna card
Replace logic board
Audio IO (front headphones)
Reseat front panel board
Replace front panel board
Replace logic board
Audio IO (rear audio line in; rear audio line out) 
Check Sound settings in System Preferences
Replace logic board
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