This problem developed while I was working on a "no HD Audio" problem. Previously the system booted fine. All systems go except audio.
Power off while inspection audio cable connections. When I turned system on, fans come on, I think I hear the hard drive, reset light is on hard and a green light on a CD is on. Screen is dark.
I have repeated this with all IO except keyboard and mouse disconnected. No change.
I have measured the power supply outputs at unused connectors. All measure good except 3.3v which I cannot locate on a connector other than the one to the motherboard. Did not want to probe in the connector housing. Assume it is good also.
Is the 3.3 volts by any chance the power Good indicator.
I have received the replacement MOBO but have not yet installed it. I find that there are too many things that I know nothing about and have been reluctant to do so until I do more research.
I must relocate the processor and the fan assembly. I just learned that I need to use a thermal paste. Never done that before. The processor seems to be an easy task but expensive if I screw up.
The big road block - BIOS. The chip looks different (numbers) so I am not certain I have a Bios on board at all. May need to remove the chip and get it flashed somewhere. I know nothing about the original content.