you could open it and pull two boards fully out.
test one board
if it works one of the other two boards may be shorted.
if it does not work you may be testing the shorted board.
so pull that one board and test one of the other two 2️⃣
you end up testing all three boards one at a time.
if it never works it is likely the psu is dead. ☠️
quote this post to see how to code a log