Jaz wrote:
A have a Maxtor 20GB 2B020H1 which is doing the spin-up then spin-down
thing. The controller says ATHENA ATA2-PLUS, FBII 301430100.

I found this site http://www.hddtech.co.uk/MaxtorFailureSymptoms.htm
and my symptoms match precisely. So I bought a working 2B020H1 used.

I swapped the contoller but the drive isn't recognized at POST. I
swapped the controller back to the spare-parts drive and that one
works fine. Worth noting is that with the spare controller, the
original drive no longer spins down after spin up.

Then I noticed that the spare controller part number is slightly
different. The new one reads "ATHEN II/POKER". What's interesting is
why this controller would not be detected by the BIOS when attached to
the old platter assembly. I verified that the geometry and the Maxtor
part numbers are both the same.

Anyway, aside from trying to find another spare controller that
matches exactly, and before I resort to an $800+ professional
recovery, is there anything else I should try?

You might try a local small computer shop that can give you a realistic
price. It's called competition. I have dealt with some that allow you to
wait and watch if you tell them you have someone else that is willing to do
the same. Works for me.