are you using an intel atom board by any chance?
I had this happen when I used that, it wasn't due to the power supply. it was actually due to the board.
I have been using a M2-ATX for several months, inside a pcVoom box.
The way it worked was, when accessory power was applied, the pc lay domant for about 45secs before completely powering up.
I say completely, because I would see a number "45" appear in the top left corner of the screen after about 10secs of accessory power, and about 45secs later, the cpu fan would startup and windows would begin to load
When accessory power was removed, the pc would shutdown after about 5 secs.
Now, all of a sudden, the pc is firing up within a few secs of applying accessory power, and not waiting for the former 45secs. The closedown timing is unaltered. i.e. after about 5sec of lost power.
The only change made was to replace a faulty dvd player.
The J6 pin is, and was, set to P1. So no change there.
Which is normal startup timeframe. 5 or 45 secs start delay?
The reason I liked the former startup delay is that I was sure I was not going to get any cranking spikes from the starter motor. Am I being paranoid?
Yes.an Atom board.
So, what you are suggesting is that the PSU is now functioning as normal, the the 45 sec delay previously was due to the mother board having some issue?
your "faulty dvd player" caused postcode 45 = post device initialization
Thank you. I will now go back to sleep