[amagab]

I just replaced the logic board and ram on my Powermac G5 1.6ghz. I still can't get it to work.

How do I find out if the CPU is bad?

Thanks!

[Lateralus]

...what's wrong with it?

[Waragainstsleep]

The only ways to confirm a bad CPU are to have the CPU fail hardware test, swap it out for a known good one, or swap the rest of the machines essential parts with known good ones.

If the unit is completely dead, its either the power button board, CPU, Logic or PSU with PSU most likely. If it powers up at all, its more likely the CPU or Logic. If you have swapped the logic board for a known good one and the symptoms persist, its probably CPU.
Reseating RAM, CPU and video card can cure a lack of video output.