ATX power supply mod 12v to max V

[JohnnyO]

I need some help with a WT7517 chip used as control in an ATX power supply ( Dell model H305p - 00. I can't find the circuit diagram ? )
I have the data sheet for the WT7517. I want to change the 12v power supply output to its max value by removing control of this output from the control chip. Can you suggest the best method ? I realise that the output capacitors will require change to higher voltages.

www.techpowerup.com/articles/160/images/WT7517.pdf

 

[JohnnyO]

It would help if you could direct me to an ATX pwr supply schematic that uses a WT7517 control chip.
I have checked many ATX power supplies but I have found none that use this particular chip .

 

[dave9]

Trying to completely reverse engineer a particular PSU and re-engineer it to do what you want (which is what exactly? Trying to make the 12V rail a HIGHER voltage than 12.0V and operate without load on the other rails?) is beyond the scope of a forum topic.

I wonder why you feel the need to do this. A used PSU like that, rated at only ~305W among all rails, is not particularly valuable and in mATX size, used no less, not particularly robust. I could see repairing it if in a Dell system and a replacement was hard and/or expensive to come by, but this particularly PSU would be straining to provide 20A @ 12V and you want to push it higher than that?

You won't need to change the output capacitors unless aiming for lower ripple. They're bound to be rated for at least 16V, and you won't get over 16V out of the 12V rail.

You're better off just buying a 20A switching PSU with an adjustable output at least up to your target voltage. Which control chip it uses, is sort of the least of the issues though seeing its pinout, will help you trace the PCB tracks to find the resistive divider in the feedback loop.

 

[JohnnyO]

Thanks Dave for the good advice. It's more a project than a need, and yes if I needed a PS I could buy one. I felt sure that I could at least get 20v dc by removing the regulation and could if necessary further modify the secondary side (removing the centre tap earth etc.) to get up to 30v dc. The idea was to have an adjustable output 0 to 20v and up to 5amps using a DP30v5a for the final stage. I have all the "bits" for this, the only thing missing to get me started is the schematic. The control chip is on a 17 pin (soldered) motherboard and I feel that this could offer possibilities if I view the schematic.