So I bought a second Seagate ST-225 "winchester" disk off ebay. I got it for the starting bid, nobody else made a bid! Result. I have connected it to my PDP-11 and used my "XXDP booting from ODT" trick to format it. Here are the results:
This is good news, the drive seems to be in good shape. Since then I have copied some RT-11 files to it and made it bootable. So I have a spare.
A colleague at work gave me a Seagate ST-225 "winchester" MFM hard disk. This disk is the same as the RD31 used in PDP-11's (a 20meg drive). It has been sitting inside my PDP for a while, but I could not format it. I tried to make an XXDP boot disk, which has the formatting program, but it halted the machine when I tried to use it. RT-11 cannot format fixed disks. However, I managed to find other means to get XXDP onto my machine. Here is the disk format program in action:
Nice! What I did was boot XXDP in the SIMH emulator, start the ZRQCH0 formatting program and then dump the first 56k of memory to disk. I then used a little C# utility I wrote to turn this dump into machine instrictions that could be entered into memory via ODT. It took about 2 hours to send the data over a 9,600 baud serial line. Still, it worked a treat! I have a formatted hard disk in my machine! I haven't managed to make it bootable yet, but I have copied some files to the new disk. I need to upload some photos...