I've not built one of these myself, but I'll help where I can:
Those small ICs are optocouplers. They close the feedback loop from the primary switching side to the secondary regulation side. They are needed. The second small transformer may be one of two things, either a small transformer for the 5v standby (the most likely explanation), or another part of the feedback loop. You may need to rework the 5v standby section accordingly.Originally Posted by Zznakie
The PWM circuit will provide the regulation. It hooks up to the optoisolators on the AC side. Did you forget this circuit?Originally Posted by Zznakie
This is not a trivial mod, you really do need to know what you are doing, most power supplies are slightly different.