Powersupplye

The specs seem to be very similar to the OEM adaptor, but why are you using a Plextor adaptor with a Seagate unit?

Did the external drive work with the original power supply?

Thanks for reply, but do you now for sure if i can use this power supply

Presuming the polarity is the same, the specs are similar (12V at 2.0A). Most replacement Personel Storage 3100 OEM PSU replacement are 3.0A, but a few sites also sell a 2.0A unit; therefore I'll presume that 2.0A is enough.

Did it work fine with the original PSU?

The polarity is indeed the same (centre pin positive):

http://s3.amazonaws.com/kpsurplus_images/1aa78002f8a8e3...

Identifying Maxtor External Storage Power Supplies:
http://knowledge.seagate.com/articles/en_US/FAQ/186849e...

As you can see, the Plextor PSU meets the requirements. Did that external drive work before or is it a unit that you got for free and hope to get working?