exxos's Atari, Amiga & retro forum

I've been looking into alternatives to the 520ST external power supply and as I've been looking into them I see the following pinout showing +5V, +12V and -12V inputs.

From what I've read with the STF and newer, the +5V is the primary input for running most of the board, the +12V is for the floppy drive and video circuitry (please correct me if I'm wrong).

Given that the original 520 doesn't have a floppy drive to power, why would it need the -12V input?

-12V is for RS232 stuff on the ST. STF had a built on negative voltage regulator, which the ST does not have.

Ah, makes sense! Thank you.

You can quite easily use a Pico PSU for a short-st, see my blog:

https://www.exxosforum.co.uk/forum/viewt ... f=9&t=4617

This is what I built: https://www.exxosforum.co.uk/forum/viewt ... &hilit=PSU