[cctalk] Re: Drum memory on pdp11's? Wikipedia thinks so....

RS04 is a fixed head disk, similar properties as a drum but shape-wise it's a flat platter with heads on one side. The "lubricant" bit reminds me of our college RF11 swap disk (for RSTS/E). When we got the RP04 it was no longer so interesting so it was not configured in, but it was still powered up. One day I noticed that the "timing track error" light was lit, and since the system was under contract we called DEC field service to repair it. The local tech checked things out and realized the drive was not spinning even though it had spindle power. Oops. He took the drive apart and discovered that the heads had landed, and melted so they were essentially hot-melt-glued to the platter. Those drives use rather low powered motors, intentionally, so with the heads stuck it would not spin up. He ended up replacing all the heads and the platter, not sure about the motor. Got an alignment disk and timing track writer from Maynard, and had to figure out how to use these -- the documentation was sparse, to put it politely. In the end, everything worked. Oh by the way, I don't think that field repair of a drive like that was a standard procedure, but for Jim Newport this wasn't a big deal. paul