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22288Re: [midatlanticretro] How can I tell if my SMD disk head is crashing?

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  • c f
    Aug 12, 2011
      Darn, I was hoping the heads might just make some kind of whistling noise when loaded or something.


      I didn't notice any kind of oxide flakes/chunks/powder inside the dust cavity when I removed the pack (although I have not tried wiping the inside with a clean white cloth to check for really fine particles yet). I will look for a way to remove the dust cover - I haven't been able to figure out how to get around the interlock thing yet (although I haven't tried much).

      If you lift up the drive's main shell, there is a little window that lets you look into the drive cavity and see both the disk platters and the head assembly if you shine a light into it, although it was impossible to determine if a head was making contact or floating just by looking.

      I do actually have a 2nd drive (in pretty bad condition) that happens to have a full set of heads, as well as 1 spare head still in a box. I'm not sure if the 'servo' head is identical to all of the others, but I believe it is. I also have a tester with head alignment card, as well as the little head adjustment tool thing, and a CE pack for calibrating things. Unfortunately I'm also pretty pressed for time.

      One final comment - I reconnected the voice coil and attempted to let it go through its automatic startup process. The drive powers up, gets up to speed, and then attempts to do a 'load seek' operation, where the coil drives the head assembly forward about 2 inches or so, and then retracts quickly and triggers the 'fault' light. No whining noise or anything, though. I think this means that the servo head is failing to detect the dibit pattern on the out



      -Chris

      On Fri, Aug 12, 2011 at 7:31 AM, Mr Ian Primus <ian_primus@...> wrote:
       


      --- On Thu, 8/11/11, c f <christopher.h.fenton@...> wrote:

      > 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.

      Eek. That sure does sound like a head crash...


      > 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).

      You can remove the dust cover to get a better look. I'm not sure about the smaller packs, but on the 300mb disks, look inside the center spindle - there will be a round hole in the center. By inserting something into that hole (like a pen), you can disengage the ball bearing catches that hold the top cover on, and lift off the dust cover. From there, use a flashlight to check for scratches on the disk surface.


      > I then retried the same procedure, and the high pitched whining noise
      > started again right away when I loaded the heads.

      That sure seems to point to a head crash, since it only whines when the heads are loaded. You should also be able to inspect the heads themselves. Look for any oxide scrapings or buildup. Did you clean the heads before you tried loading them?

      It's possible you're hearing something else... but a head crash should sound like metal on metal. A real terrible head crash would result in lots of brown oxide dust. Examine the pack for any trauma.

      Even if it did crash, all is not lost - heads do turn up. I know a guy that might have some. I've never done a head replacement though - but it is documented in the manual (and it's a lot of work...).

      -Ian


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