I had similar symptoms with my Powermac 2.0 DP. After exhausting all the simpler fixes I was left with power supply, motherboard or CPU. For me, one of the CPUs was bad. I found this out my flipping the CPUs. I took both out, and then put CPU 2 in CPU 1 slot and CPU 1 in CPU 2 slot. The machine then booted showing only one of the CPUs as functional. The computer worked fine in this setup, though I didn't do any prolonged testing. I purchased and installed used CPUs from ebay.
The hardest part of working with the CPUs was taking the cover off. Once the cover is removed, the cooling fins are sharp and you need a long handled driver to remove the CPU screws To get an idea of what is involved, here is a breakdown with pictures that I used: http://g5.bhmm.net/. You would also need to obtain a copy of the Apple service disk to calibrate the fans. -- You received this message because you are a member of G-Group, a group for those using G3, G4, and G5 desktop Macs - with a particular focus on Power Macs. The list FAQ is at http://lowendmac.com/lists/g-list.shtml and our netiquette guide is at http://www.lowendmac.com/lists/netiquette.shtml To post to this group, send email to [email protected] For more options, visit this group at http://groups.google.com/group/g3-5-list
