RD53s and RD54s

Hi, I've decided after many years of accumulating PDP-11s that the time has come to restore a few of them to operational condition. I've decided to start with some QBUS machines as they give me the best chance of a warm fuzzy feeling of success. The first thing I've decided to do was to retrieve all of my RD series harddisks and establish which ones are still operational. I've initially started with 4 RD53s and 4 RD54s which I've connected upto an 11/73 and used XXDP to format. All RD54s have formatted perfectly, confirming their reputation for reliability. However none of the RD53s would format, which I guess also backs up their reputation. I had hoped at least a few of the RD53s would have still been usable (I have about 6 more I've not tested yet). Does anyone have a RD53 still in working condition? Is there any point in keeping the duff drives or should I consign them to the skip? Toby -- This message has been scanned for viruses and dangerous content by MailScanner, and is believed to be clean.