I have a computer PSU that accepts 120/240 and auto detects and is capable of 1200 watts (next model up is 2000 watts) and I can not see a transformer in this thing! I have not come across a psu that doesn't have a transformer of some sort (sometimes multiples). I want to take it apart but it is pretty small and I fear reassembly correctly. For any that question, this is a server PSU by one of the top server manufacturers so it isn't some cheap chinese knockoff.

How is this possible or am I missing something!?

 

There's a transformer in there: it will be running at a much higher-than-line-input frequency, though.
As a result it will be of much lighter construction than a 50/60 Hz unit.
Here are some pictures