Shelving the 2003 based pc power supply I routed through my scrap box and found an antique 230w c power supply, pre P4 connector.
It has a Tl494 (making mods so much easier) and a weird device marked LS 168A that I cant find any data sheets for, I think its a psu supervisor, it has tracks to the 3.3, 5 and 12v outputs, and tracks to the Tl494, I tried breaking the track that goes from this to the '494 to see if I could turn the handy trim pot on the board so the o/p would go past 12v, didnt work.
So fix it or break it I just unsoldered the LS168, and tried again, the supply powers up without the green power up wire grounded as hoped, and I can wind the o/p up to 15v where the tranny goes nuts and the supply outputs 30v, probably because the '494's feedback pin is grounded by the pot, the manufacturers probably thought it'd never get to ground before the supervisor shuts it down.
So this idea looks as though it might work, but if the overcurrent protection is also done by the '168 then it isnt exactly going to be reliable, also this psu doesnt give more than 8 amps on 12v, I really need 15.
Still searching for data on the 2003 ic in my other psu, or even the 1001 in a nicely made dell psu I just found.