Washing machine drives

One of my first jobs was as a weekend operator for Tektronix' CDC Cyber 73 computer. The machine was powered off at night. At around 9PM each night, the entire system was powered down. Weekend operations started up a 8AM on Saturday until 6PM, then Sunday from 9AM until 6PM. When I'd come in, the machine was turned off, and I had to go through the long rows of CDC "washing machine" type disk drives and power them up one at a time. Couldn't power up more than one at a time, as the surge load would cause breakers to pop, and that was definitely not a good thing as a drive is spinning up. I'd have to hit the power on the drive, and wait about 45 seconds for the drive to spin up enough that the main surge was over with before I could hit the power switch for the next drive. It was New Year's Day (don't remember the exact year..probably late '70's...maybe 1978). It was a Saturday or Sunday, can't remember for sure. Anyway, I came in and started the power up routine. I had powered up four or five of the drives when suddenly, the first drive that I'd powered up started making a very strange shrieking noise, followed very quickly by a very loud BANG!, then what sounded like the aftermath of an auto accident. I looked back at the drive (I was perhaps 6 feet from it when this happened), and it was engulfed in a cloud of smoke. Immediately thereafter, the klaxon went off indicating that a Halon dump was imminent. I didn't know if the smoke was from something on fire in the drive, or just from the headcrash, so I bolted out of the room as fast as I could and let the Halon dump. I didn't want to take the chance that there was a fire, and have it spread. When the Halon dumped, the fire system automatically contacted the fire station that was next door to the Tektronix campus. I waited outside the room until the firemen showed up, less than 2 minutes from when the Halon dumped. They went in with respirators and checked to make sure that there was no fire. Everything was OK, although the area around the disk drive had small shards of a metallic substance on the floor. They set up fans and aired out the room. I was then able to go back in. My Lord, what a mess. It appeared that the disk pack suffered a catastrophic failure. Don't know if it was because of a head crash, bearing failure, or simply a pack failure. Whatever it was, it completely destroyed the drive. The CDC drive (can't remember the model number, unfortunately) was very well-built. The enclosure for the pack was a huge metal casting with very thick walls, acting as a scattershield for the pack. The shards of metal around the drive were not from the pack, but apparently from the motor, which stopped very violently and broke its mounts. The pack was reduced to bits, which were all contained within the drive enclosure. The smoked Plexiglas window in the lid of the drive that allowed a view of the pack looked like it had been shot with a shotgun, but didn't break. It was very thick Plexiglas. I called our CDC rep -- we had two onsite engineers that were devoted to the support of our system. Come to think of it, it was a Sunday (so it had to be 1978), because one of them was at church and couldn't be reached, though he was paged. I also called my boss, who had partied the night before as a result of the New Year's holiday. He said to hold off trying to do anything until he got there. After about an hour, one of the CDC guys showed up, followed shortly thereafter by my boss, who looked a little worse for the wear :-). The CDC tech. removed the drive were OK. The drive that failed had the boot pack on it, so we had to change the switch-based boot program (an array of toggle switches that contained the PPU code to coldstart the machine from tape, which then read in a disk book loader to boot from disk), and mount a backup boot pack on one of the other drives. We were able to bring up the system just fine, and do normal operations for the day. Later in the day, a replacement disk drive was received, the system downed, the new drive put in place, and we resumed normal operation. According to the CDC rep., the failed drive was a total loss. Thank God that the drives were so well-built. I can't imagine what would have happened to me if pieces flew out of containment. I always had a lot more respect for these drives after that event. Rick Bensene