Hi and congratulations for your haul!
The dual 2.7 should be an early 2005. You should have a look at this: http://www.cwu.edu/~pruittj/powermac_g5.pdf
There are also pdf manuals for the other G5 generations on the net. I've not looked yet, maybe this model has diagnostic LEDs on the motherboard which could help with finding the solution.
Also found this, maybe helpful: https://discussions.apple.com/thread/2620983?tstart=0
About the third unit, this is most likely a dual 2.5 or another dual 2.7, thus watercooled and prone to leaking. I have myself a dual 2.5 which has some white stuff under the logic board. The first step is disassembly and inspection of the damage. Some are still working with this symptom, bit I won't take the risk. Here is a pinned post about overhauling a G5 LCS. In your case the damage is unfortunaly quite advanced I'd say, as your PSU already fried/died. I don't know how the other components react to a sudden PSU death, but it could be worth checking how it looks underneath the cooling system. If not saveable, you have an unit for parts.
Cheers,
Nicolas
The dual 2.7 should be an early 2005. You should have a look at this: http://www.cwu.edu/~pruittj/powermac_g5.pdf
There are also pdf manuals for the other G5 generations on the net. I've not looked yet, maybe this model has diagnostic LEDs on the motherboard which could help with finding the solution.
Also found this, maybe helpful: https://discussions.apple.com/thread/2620983?tstart=0
About the third unit, this is most likely a dual 2.5 or another dual 2.7, thus watercooled and prone to leaking. I have myself a dual 2.5 which has some white stuff under the logic board. The first step is disassembly and inspection of the damage. Some are still working with this symptom, bit I won't take the risk. Here is a pinned post about overhauling a G5 LCS. In your case the damage is unfortunaly quite advanced I'd say, as your PSU already fried/died. I don't know how the other components react to a sudden PSU death, but it could be worth checking how it looks underneath the cooling system. If not saveable, you have an unit for parts.
Cheers,
Nicolas