That is indeed an 800K drive.
Some possibilities:
1) You bent a connector pin when reinstalling (or your cable is otherwise defective).
2) Your floppies were written by a functioning, but misaligned, drive. Try reading disks from other sources. Also try formatting a blank disk in the new drive and see if it completes the operation successfully.
3) Your floppies were written correctly, but your new drive needs a head alignment. Again, try formatting a blank disk. If it can do that, your new drive is basically functional. If it's unable to do this, then the drive would seem to be borked.
4) Every floppy you tested is actually bad.
From the fact that it thinks every disk is write protected, it would seem that your new drive has a problem (or the connections to it are messed up). Take a look at the write protect microswitch sensor in the mouth of the drive to make sure that it isn't stuck.
Some possibilities:
1) You bent a connector pin when reinstalling (or your cable is otherwise defective).
2) Your floppies were written by a functioning, but misaligned, drive. Try reading disks from other sources. Also try formatting a blank disk in the new drive and see if it completes the operation successfully.
3) Your floppies were written correctly, but your new drive needs a head alignment. Again, try formatting a blank disk. If it can do that, your new drive is basically functional. If it's unable to do this, then the drive would seem to be borked.
4) Every floppy you tested is actually bad.
From the fact that it thinks every disk is write protected, it would seem that your new drive has a problem (or the connections to it are messed up). Take a look at the write protect microswitch sensor in the mouth of the drive to make sure that it isn't stuck.