Ok its been years since Ive put my ATX power supply in my Amiga 4000 but if I remember correctly doesn't the ATX power supply need a jumper between two of the pins on the ATX connector in order to turn it on? I built my own adapter for it and my 4000 has been running fine on it for years.
Also are you sure that all the pins are actually connecting in the Amiga 6pin connector? I bought one way back on ebay and it never worked either untill I found out that one of the pins wasnt even connecting to the other inside the connector.
