SMPS problem with a SUN Ultra 2 machine

An ultra 2 machine had a failed SMPS. So a new one was
procured. The new one has come ( Zytec EP071235-E 350 W )
and we fitted it. The machine booted up on turning ON the power.
after running it for 5 minutes and making changes in dfstab
and auto_home files ( the machines configuration need to
be changed ), the machine was powered OFF using the poweroff
command.
The trouble started here..
the machine could not be powered ON..
the familar power ON beep never comes now..

i wonder what must be wrong ?
how do i go about solving the problem..
one broot force method is the process of
elimination ..
to unpopulate all the cards, and memories
and try booting..
if power ON is possible continue till
it doesnt ?

However i would like to seek expert's view before that

the cards, memories and try booting