[ttk]

I have searched for this answer and have not found the same symptoms listed.
G5 dual Model A1047 Sn XB34705VQES (early 2004 I think/ 8 memory slots)

This was powered down and the surge suppresor power switch was turned off when I left for 1 month bit was still plugged in not sure what happened with power while I was gone.

Now when I hit the powwer button, it turns on, the red LED flashes once and the fans react with a slight movement and then nothing.
If I hold the power switch the light stays but no bootup or discs spinning

I have removed all the RAM,disks and interface cards. Replaced the battery and reseated cables.

[seanc]

Check this out. Apple - Support - Power Mac G5 Repair Extension Program for Power Supply Issues

Apparently your serial number is not covered but I checked it on Apples site and you have 100 days more of Apple Care.