No signs of life from the PSU but there normally
isn't until powerup and the
LED lights up.
Usually the vent fan will start spinning right away. If the fan doesn't
even jerk, then the PS may not be doing anything. I've used that to track
problems in some macs before (Mac PSs tend to be "short resistant", at
least that is what I've found. If there is a short somewhere, the PS will
power itself back off rather than fry itself... in those cases, the fan
usually jerks as the PS comes on and cycles right back off)
It is starting to sound like the PS is dead.
There are no additional troubleshooting steps listed in the Apple tech
manual for the IIfx (actually, there are no troubleshooting steps at ALL
in that manual).