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Finding suitable replacement stepper motors

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    Finding suitable replacement stepper motors

    I have at least a couple hard drives that would be functional if the stepper motors would work. I have learned essentially how stepper motors work, but I have no idea how to spec one so I can find a suitable replacement. The two I want to focus on are both from WD93044-A hard drives, 43 MB., 1990. The stepper motors are identical sizes but different brands/models. The one motor that does have a label says:

    0829
    59-004020-000
    MSJC400A71
    Sankyo Japan
    I appreciate any advice on specking stepper motors and sites to order them from.
    Sattinger's Law: “It works better if you plug it in.” Corollary: “It works even better if you plug it in correctly.”
    "The simplest solution is the most likely solution." --My paraphrase of Occam's Razor
    "You can get [a computer] like yours at a garage sale for, like, fifteen dollars," --Strong Sad, sbemail #33

    #2
    It's been awhile, but as I recall, the relevant parameters are, of course, voltage and current ratings, step angle (degrees per step), maximum step rate, number of wires (3 (rare), 4 or 6) and, of course, physical configuration. That's off the top of my head and I'm sure that I've forgotten something.

    A word of warning--some of the hard disk drives use a "ballistic seek" to cover longer distance seeks, taking into account the mass of the head+motor assembly. The characteristics are usually programmed into the MCU running the drive mechanicals. It's possible that substituting a stepper with different mass might run afoul of that.
    Reach me: vcfblackhole _at_ protonmail dot com.

    Comment


      #3
      Are the stepper motors you have dead or burned out? Or are they just stuck? Applying a couple of drops of light machine oil to the bearings and working them back and forth gently can often bring them back to working order.

      Comment


        #4
        If the motors are actually dead (rare, more like stuck) then these HD's are cheap on ebay so maybe look for one as a 'for parts'.

        The next issue is removing and refitting without damaging the platter. I don't know how they drive through the casing, so you might have to go internal and removing the head drive from a multi-platter drive might be, err, challenging ?
        Current fleet
        TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225 Apricot PC - Apple Performa 6200 - Apple Mac IIcx - Osborne 1 - ACT Sirius 1

        Comment


          #5
          I already bought the second drive as "for parts" to try to salvage the stepper motor from it. I couldn't get the stepper motors to move in the installed-in-the-computer condition. I used 3-in-1 bearing oil on them, a drop or two a day for days, but no change. This is a small project I started months ago and am trying to finish to not only give closure and make at least one of the drives usable, but also learn something (stepper motors and their specking) to hopefully make myself self-sustaining in that matter.

          It sounds like the industry standard size of stepper motors either don't exist (each application is a custom motor design) or there are so many standard sizes that it's like an ocean of them. Can the numbers on the label that I gave above help?

          I've already removed one of the motors (yes, had to open the platter chamber to undo the nuts on that side--ugh). That same motor is currently disassembled. I couldn't find anything mechanically wrong with either of them, including sticktion.

          Is there a failure mode for the stepper motors that is electrical that I'm not aware of?


          Sattinger's Law: “It works better if you plug it in.” Corollary: “It works even better if you plug it in correctly.”
          "The simplest solution is the most likely solution." --My paraphrase of Occam's Razor
          "You can get [a computer] like yours at a garage sale for, like, fifteen dollars," --Strong Sad, sbemail #33

          Comment


            #6
            It's been a long while since I worked on disk drives....
            As I recall the motor driver failure was common. Usually one phase shorts and always powers one winding on.
            If you can move the rotor with power off but the motor doesn't move with power on it may be the driver.

            Failure of the stepper motor was rare and mostly dry bearings or an open winding.

            joe

            Comment


              #7
              Remember the platters are very very sensitive to anything. Just touching them is enough to cause a head crash when spinning.

              If you have in anyway got dust on them, then the only thing you can do is set them spinning without the head driving in. You might be lucky and fling any contamination off.

              I must admit, unless there is something essential on these drives, evenI would give up on them.
              Current fleet
              TRS80 Model 4 - BBC B - Tatung Einstein - PCW9512 - PET 3032 - C64 - ZX81 - Spectrum 48K - Amiga A500 - Apple II europlus - Apple iMAC G3. Sharp MZ-80K. - IBM 5160 XT - Multibus 286/10 - Micro PDP 11/73 - Rainbow PC100A - MicroVax II - MicroVAX 3100, 3300, VAX 4000 VLC & 4000 Model 96 - AlphaStation 225 Apricot PC - Apple Performa 6200 - Apple Mac IIcx - Osborne 1 - ACT Sirius 1

              Comment


                #8
                Okay, I guess I myself will put them up for sale as for-parts-only. Darn. At least they are a matched set, so whoever gets them will have parts from both to work with.
                Sattinger's Law: “It works better if you plug it in.” Corollary: “It works even better if you plug it in correctly.”
                "The simplest solution is the most likely solution." --My paraphrase of Occam's Razor
                "You can get [a computer] like yours at a garage sale for, like, fifteen dollars," --Strong Sad, sbemail #33

                Comment


                  #9
                  Hello
                  The stepper motors you are looking for are "12volt 1.0amp 1.32ohm 400 step/rev"
                  I have removed a number of them from old drives and given them to the school for the science class.

                  As mentioned above, it is extremely difficult to replace these without crashing the heads...

                  CM
                  --------------------------------------------------------------------------------------------------------------------------------------
                  There are only 10 types of people in the world – those who understand binary, and those who don’t.
                  WEEKS of Programming can save HOURS of planning !!!
                  There is nothing like the Smell of Molten Projects in the Morning !!!

                  Comment


                    #10
                    Originally posted by CMAC View Post
                    The stepper motors you are looking for are "12volt 1.0amp 1.32ohm 400 step/rev"
                    Thank you! Is there a model number or site that I can go to order more if I need?

                    Other thoughts: Is there a good YouTube video or website article that tells how to diagnose and repair a stepper motor driver? Since this topic came up, I suppose I'd like to learn that if I can. No sense worrying about ruining the hard drive contents now, I guess, if I mess up.
                    Sattinger's Law: “It works better if you plug it in.” Corollary: “It works even better if you plug it in correctly.”
                    "The simplest solution is the most likely solution." --My paraphrase of Occam's Razor
                    "You can get [a computer] like yours at a garage sale for, like, fifteen dollars," --Strong Sad, sbemail #33

                    Comment

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