I'm chiming in a bit late here, and while I'm not recommending this as some sort of tested setup, my knowledge of DC power driving digital circuitry tells me that (barring any really weird stuff going on) the PC PSU's 3.3V output will drive the 2.75V circuit just fine, and the 12V output will similarly drive the 10V circuit just fine.
I would add a hole and a fan as others have said- generally the only consequence of overdriving the voltage a little like that is increased heat.
-SS
NUNQUAM NON PARATUS
--- In xl7@yahoogroups.com, "lz303" wrote:
>
> ...but as i said before i am not an electrician i need detailed instructions...
>
> I checked Powdec but no similar power supply there...
>
> So there is not one similar power supply on the market right now? Hmmm...
>
> If there is no similar one available i would go for the PC PSU just to try if the XL7 works again .
>
> 5V 12V -12V and 3.3V are no prob but what about the 2.75V or the 10V?