Thanks to the people on this list and one other (thanks Matt!) I have got my RD53 working reliably now. I currently have it installed in a MicroVAX 2000 with 6MB of memory running MicroVMS 4.6 and DECnet. I had to remove the old bumper which had become sticky. But to make the disk work I had to replace the bumper, so I used some folded over post-it notes taped to the top of the head assembly. This seems to work for now, but I fear a better solution is needed.

I also get a grinding noise which becomes apparent after the disk has warmed up. I think this comes from the graphite pad underneath. I plan to loosen the mounting bolts a little more to see if that gets rid of the noise, but I am wondering if there is any other way to get rid of it. Why is the graphite pad needed? What would happen if I removed it?