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22286RE: [midatlanticretro] How can I tell if my SMD disk head is crashing?

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  • Dave
    Aug 11, 2011
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      When these disks were in common use I seem to remember that the Customer Engineer had a way to remove the dust cover and had some kind of arrangement with mirrors to check the pack. However its been a long time since I worked with these.
      However I do seem to think a high pitched squeal meant head contact.
      It was far to easy to wipe out several drivers with a bad pack......
      ... or by sitting a drive next to a closed off chimney so it sucked all the soot from the chimney in. 
      -----Original Message-----
      From: midatlanticretro@yahoogroups.com [mailto:midatlanticretro@yahoogroups.com] On Behalf Of c f
      Sent: 12 August 2011 04:36
      To: midatlanticretro@yahoogroups.com
      Subject: [midatlanticretro] How can I tell if my SMD disk head is crashing?

      I've been working for a while on reviving/rehabilitating an old CDC 9762 disk drive (each disk is a stack of 5 14" platters, with the middle 3 having 5 data surfaces and 1 servo surfaces - the drive has 6 read heads). I finally got to the point where the drive was cleaned up, so I spun up a disk pack and manually loaded the heads by just disconnecting the servo coil and moving it with my hand (the manual says this is okay for testing).

      When I loaded it, everything was fine for a minute or so, but then I began to notice a high-pitched whining noise coming out of the drive. I retracted the head assembly, stopped the disk, and attempted to inspect it and the head assembly. Everything looked fine as far as I can tell (the disk is a bit difficult to examine, as you need to look at it through the tinted plastic of its cover). I then retried the same procedure, and the high pitched whining noise started again right away when I loaded the heads.

      Does anyone know if that noise means one or more of the read heads is contacting the disk? Or could it just be a whistling noise produced by the head being close to the surface? The disk cabinet had been lined with a thick layer of noise-deadening foam that I had to remove, and I've never really worked with one of these before, so I'm not sure what it's supposed to sound like. Any advice would be appreciated.

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