[SOLVED] power up the MB by external 12v PSU?


Oct 20, 2015
title and bold.

I want to build a custom case for my PC, as minimal as possible
I run mATX motherboard with 57mm cpu cooler height (no GPU).
My setup is fairly small, and according to my measurements I consume on idle 30-35W with peak at 75W

I thought about getting flexATX PSU which will probably fit my needs but these things barely exists in my country, and shipping it internationally will cost a lot.

A better thought occured to my thoughts, about running it via external PSU.
I've got lots of laptop chargers and power supplyers that can support 12V at high currents reaching 100W or even 150W.

I'm okay with electrical wiring and modifying stuffs so I'm ready for a challenging project here
(anyway I'm gonna create the case from wood and lots of carpentary work so..)

so here's my question:

Can I power up the MB using external 12v power source? also, what would I need for that?

As I understand by now, the MB receives around 20-30 wires from the PSU which mainly includes:
  • 12v wires
  • 5v wires
  • 3.3v wires
  • others?
so firstly, how many 5v and 3.3v wires are there, and is there simple way to create them without really using DC-DC converters or gross stuffs like that?
also, about the "others" stuffs (like the one that sends back the PSU signal that the MB went off so it can go idle to save power), what exactly are those cables?
I couldn't find any specsheet that declare specifically what each cable is for

So basically, what wiring job should I expect here?
Also, is there some more things I should be concerned here or did I covered it all?

Much appreciate any help here.