i've been through about 5 DDS drives. same symptoms. i can't say i'm surprised, we're working with dinosaur hardware here, yknow?
let me clarify: i've been through about 5 DDS drives *that i successfully flashed with the audio firmware and were able to mount and read audio tapes*. for every drive i was able to flash successfully, i'd buy three that wouldn't even flash.
this is all with a known-working model, too. i didn't much mind because even after failing to flash it with the audio firmware, i could still resell them as working backup drives on ebay. in most cases, putting the right keywords in the auction headline would actually fetch me a slightly higher price than i'd paid for it a couple of weeks before!