No boot, No display, no signal and white power light flashes once

Could be loose, missing, wrong RAM. So if you changed the RAM put back the original. If you haven't changed the RAM inspect it for damage and check that it is "clicked" in.

The # and position of the RED LED is important to diagnosing what it means.

LED 1—CPU A:

LED 2—Overtemp:

LED 3—Power On: red—the main power is on

LED 4—Trickle: yellow—Power Mac G5 is plugged into the wall correctly

LED 5—Open Firmware good: green—no problem

LED 6—CPU B:

LED 7—Checkstop:

IF the Red LED you see is not #3 then you have CPU/Logic Board problems and as a DIY solution replacement is the preferred method of choice (Adding/removing/repairing Logic Board components are not really DIY projects-they require special tools, materials and experience).

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