This let's you replace the Atari ST power supply with a board that let's you use Pico PSU as power supply. You will get the mod board & 8 heat shrinks. You will need a rudimentary soldering skill and know how to use heat shrinks for this mod. There are tutorials on YouTube. To install this mod, you need to take out the original power supply board but keep the metal chasis on the motherboard. Then you will need to cut the 6 pin plug to the motherboard at appropriate length and solder matching colors to the mod board. Red wires to red wires. Black wires to black ones. The only exception is the blue wire on the plug which is soldered to yellow wires on the mod board. And use heat shrink after each soldering to insulate the wires. Then solder the indicated wires to the power switch and again use heat shrink. Then screw the mod board onto the metal chasis and that's it(ideally, you should also make a bracket for the Pico PSU plug on the back of the computer). Now you can use any Pico PSU on your Atari ST though I would recommend at least 150W PSU especially if you are still using an original floppy drive which draws higher amps on the 12v rail. Also, I would recommend using a better known brand such as Minibox or RGeek just to be safe. I've found Pico PSU's to be very reliable even for powering Mega ST's with 68030 and if it ever dies, just unplug and plug in a new one.

If you prefer, I can do the soldering for you if you send me the plug. Let me know.