Well you're not going to believe this, but it seems to have come back to life again. I just sat down with it and tried various arrangements of CPU, motherboard and RAM. Eventually I got to a stage where the machine could boot into either OS 8.6 or 10.1 successfully. After that I tried adding the 4MB SGRAM stick. Then an extra RAM stick. Then the hard drive, then the CD-ROM drive. Now its sitting on my desk all closed up, all in one piece, and it seems to be working fine now. I guess the question is though, how long for?
As you said, AF, I'm certain that it could be the PSU at fault. After I got it booting off the HD, the first thing I did was boot into OS 9 and run TTP, and loop the diagnostics tests 100 times. It passed with flying colours. That puts my mind at relative ease in regards to the RAM. Either way, if it dies again, I'm going to seriously entertain the idea of doing the ATX hack. I know something in there is definitely dying - I've got it running on the internal display, and although this is quite rare, sometimes the display will flicker, and it will make a click sound, the sort of sound that comes from a relay. This only happens for a second, and it doesn't happen very often, but it does happen. Also, on some mornings when I go to boot it up, it will take a while for the display to fully warm up. Often by the time that you can see an image, the machine is fully booted and ready to go.
So yeah, thats where I'm at now. I'm actually typing this on the iMac itself right now, connected to the internet via the P3 (which died this morning, though was easily fixed, graphics card needed reseating), while listening to AC/DC - Heatseeker. Life is good
As you said, AF, I'm certain that it could be the PSU at fault. After I got it booting off the HD, the first thing I did was boot into OS 9 and run TTP, and loop the diagnostics tests 100 times. It passed with flying colours. That puts my mind at relative ease in regards to the RAM. Either way, if it dies again, I'm going to seriously entertain the idea of doing the ATX hack. I know something in there is definitely dying - I've got it running on the internal display, and although this is quite rare, sometimes the display will flicker, and it will make a click sound, the sort of sound that comes from a relay. This only happens for a second, and it doesn't happen very often, but it does happen. Also, on some mornings when I go to boot it up, it will take a while for the display to fully warm up. Often by the time that you can see an image, the machine is fully booted and ready to go.
So yeah, thats where I'm at now. I'm actually typing this on the iMac itself right now, connected to the internet via the P3 (which died this morning, though was easily fixed, graphics card needed reseating), while listening to AC/DC - Heatseeker. Life is good