The drive is just an IBM-PC type drive. The brand is Panasonic.
Either you should make sure you are tricking it into thinking the disks are double density, or you should align the heads, or you should buy a new one, and throw it in there.
FDD's are cheap these days, so that's the option I would take.
(I have tried -with success - realigning the heads, however it's much easier to buy a new drive!)
