
Open the side access panel and observe all diagnostic LEDs.Power-on LED illuminates, fans spin up, no boot tone, and the system shuts down within a few minutes Power-on LED does not illuminate when power button is pressed, but fans spin, boot tone chimes, and there is video Reset PRAM (restart computer while holding down Command-Option-P-R keys until second boot tone chimes).Check video card connector and display cable for any bent pins.Verify display is properly connected and powered on.Power-on LED illuminates when power button is pressed, fans spin, and boot tone chimes, but there is no video If the Error LED follows the processor to the other processor location, replace that processor. If only one of the CPU Error LEDs (LED 3 or 4) comes on, try swapping the processors.

#APPLE MAC PRO POWER SUPPLY VERIFICATION#
If verification fails, replace power supply. Refer to "Power Supply Verification" in this chapter. Check diagnostic LED 2 for trickle voltage from the power supply.Power-on LED illuminates when pressed in, but goes out when button is released, there is no boot tone or video, but you can hear a small click Remove the installed front panel board and test with a known-good front panel board. Test whether the front panel board or power button is at fault.Verify that processors' mounting clamps are properly tightened.Verify that processors are properly seated.Verify power supply cables are fully connected.Check that diagnostic LED 2 is on when the power cord is connected.Power-on LED does not illuminate when power button is pressed, fans do not spin, and there is no boot tone or video

Important: For troubleshooting purposes, Mac Pro (Early 2008) computers may be started up and diagnosed with a single processor installed in either the upper (CPU A) or lower ( CPU B) position.
#APPLE MAC PRO POWER SUPPLY HOW TO#
For information on how to correctly install DIMMs, see the " Memory (DIMMs)" topic in the Take Apart chapter.

Incorrect installation of DIMMs or incompatible memory will not allow the system to start up correctly. Note: Be sure to check the "Memory" and "Power-On Self Test" topics in the General Information section of this chapter. When testing a computer for the following symptoms, remove the side access panel so you can better observe or listen for fan movement.
