As both trag and Charlieman have written, reset the MLB. Not a desultory random poke at the CUDA. The CUDA is the last thing to touch before putting the metal cover back on, with good battery (3.3V or more in circuit rather than in the hand). Its job is to provide a clean-slate inventory of the hardware to the system. Pulling the Mac completely apart will have gone most of the way towards reseting the MLB, but there is more to attend than that, in that your daughter card must be properly bottomed (which may take considerable force beyond the first stage) in its slot, as must a video card in its PCI slot. Every breakable/makeable connection along the top of the MLB must be attended carefully. SCSI power, data connection and termination must be scrupulously ensured. Your original RAM was almost certainly FPM if it worked, even if unpaired, and you must take care not to use EDO alone or mix EDO into an FPM installation, despite that EDO is FPM with pretensions (such as pipelining).

Then, having cleaned, polished, blown out, plugged, installed and rechecked everything in sight, and avoided snapping off as many of the snapdoodles as is humanly possible, install the PRAM battery. Wait 10-20sec, and then hold down the CUDA switch for 40-60sec. as your last act before recladding the box, plugging in externals and reconnecting to the mains. Use the soft-power switch on your Apple Design or whatever keyboard for startup. Note down the sequence of events (or non-events): chime, raster, Happy Mac, pointer, splash screen, march of the extensions, desktop. Record your success or the poop-out point so you can post whichever. Rots o' ruck.

de