a kinf relative bought me a PICO PSU for christmas (it was on my amazon list

Links that helped me:
Troeds Page: http://blog.troed.se/projects/atari-st- ... placement/
and
Thgills thread: http://www.atari-forum.com/viewtopic.php?f=15&t=23488
Basically, all I needed to do was dismantle the old PSU, and solder the appropriate wires to the PICO, using an old motherboard adapter cable I had in my spares box. Luckilly for me, my cable -did- use the right ATX colours for the wires, so that made things easier.
Pics:
Here is the old supply, it's broken, so I'm using it for parts:

De-soldering the switch and power connector:

De-soldering the switch itself:

Separating out the wires I'll need - 1x 12v, 2x 5v 3x GND and the 'PSU on' with another GND. I've heatshrinked the other wires for tidiness.

Switch soldered up:

Trial layout:

Baseplate cleaned, and a bit of paint added, because, why not


Fitted up, using the original platic insert to prevent the PICO touching the metal base plate:

Ready to roll in my ST:

To Do: I need to make a small back plate for the power connector, but it's cold in my garage, so it can wait

Also, the spare red wire with heatshrink on it is just one that wouldn't fir in with the others, slightly annoying, but there you go. I need a better selection of shrink tubing

All the ST 'end' cables were checked with my meter and are outputting stable voltages, and it seems happy powering an STe I have here.
I'm using a 12v 5A 'power brick' to power the PICO, which I had from a previous project.