This Iomega DA-30C03 power adapters. It has two different version. One require 12V 5V 5 pins power supply, and another need 12V 5V 4pins connectors. Under same model number, but, different version. you can find those two version adapter as below link: http://www.powerpayless.com/iomega-da-30c03-ac-dc-power-adapter-din-4pin-equiv.html
http://www.powerpayless.com/iomega-da-30c03-30941702-ac-dc-power-adapter-with-5pin-equiv.html

I have the same probleme . I have a Iomega 250GBExternal hard drive. The pins that connect to the hard drive via the adapter pack have broken. The serial number is 579233448 the model no is DA-30C03 and the p/N is 31426900. I wanted to know which is the correct product to buy please

You can find a compatible power adapter for DA-30C03 / 31426900 here:
http://www.ep-mediastore-ab.de/netzteil-5v12v-kompiomega-31426900-p-80445.html


hope it helps someone