ATnoX

Introduction

The ATnoX was born out of the necessity for me to have a small adapter adapter I could use to fit AT/XT motherboards into modern cases, powering them with ATX power supplies and turning them on with a momentary switch (the standard power on button present in computer cases built in the last 20+ years).

The ATX2AT is a wonderful device (I own several of them), but I prefer to use it to test my boards and then fall back onto a cheaper alternative I can close inside a case without it feeling like a waste.

In fact, the output connector uses the same pinout as the ATX2AT, but as I still had a free pin available, I decided to include a TICK generator: a 50/60hz square wave signal required by some big-box Amigas to turn on.

Pinout

14 pin connector, front view.

                ____
.----.----.----|----|----.----.----.
| 14 | 13 | 12 | 11 | 10 |  9 |  8 |
|----+----+----+----+----+----+----|
|  7 |  6 |  5 |  4 |  3 |  2 |  1 |
'----'----'----'----'----'----'----'

1. +12V
2. +5V
3. +5V
4. GND
5. GND
6. TICK (50/60Hz depending on X1)
7. -5V
8. +12V
9. +5V
10. +5V
11. GND
12. GND
13. Power OK signal
14. -12V

Component list

TODO

Features

• -5v onboard generation via a 7905 regulator
• Momentary button power-on support
• Header for power led in case the motherboard lacks it
• Power on button included on board for bench testing
• Optional amiga Tick generator
• 4 Layer board (middle layers are +5v and GND)

Credits

• logic-4000 libraries taken from alexisvl/kicad-schlib
• ATX power-on circuit taken from skiselev/isa8_backplane
• Amiga Tick generator taken from Aminet
• Thanks to @A-Small-Mice for the printable case