One other thing. When the unit is powered on, the light above the power button is on for a brief fraction of a second, then it turns off again and the fans power start to spin.
I'm not sure if this unit has ever worked since the customer received it. Unfortunately I normally don't see the customers that drop off the computers so I can't ask.

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Well, when I went with my father to the Apple Store to have his Power Mac G5 1.6 checked out, they assessed that it was the CPU. I had come to the conclusion myself that it was either the CPU, the lobo, or both way before our visit to the Apple Store. Of course, they would choose the most expensive part to replace. My father just gave up on it for a while until he could spring for a dual 867 PMG4 MDD which he is quite happy with now.