Repair DOS-floppy with USB-Drive??

[derverstand]

Hi,

Recently I found an old floppy with fat16 on it and it has errors. What I want to do to fix it is: Create an image with dd and then try to do a MSDOS chkdsk -f . My only floppy drive is USB and the problem is, that it doesn't create a device node with the buggy disk in it. If I put a working floppy in the drive, there is a /dev/sdX, but the floppy with failure doesn't create a node. And without node no dd :<
What can I do?

Best regards!