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Thread: Seagate ST-412 stuck (spindle not spinning)

  1. #11
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    Quote Originally Posted by modem7 View Post
    My ST-412's spindle turns when only power is applied to the ST-412 (no data nor control cable attached).
    In case of use for anyone later, I have been able to reduce that configuration. In my functional ST-412, for the spindle to rotate, all I need to do is supply +12 Vdc to the spindle/servo PCB. The photo at [here] shows me supplying the +12 Vdc via the main PCB (instead of using a benchtop power supply).

  2. #12
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    All ST-412s have a spindle brake (see the OEM manual on Bitsavers--it's prominently mentioned).

  3. #13

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    Quote Originally Posted by Chuck(G) View Post
    All ST-412s have a spindle brake ...
    I don't think this is correct. Mine does not have a spindle brake, nor did it ever. There are no mounting holes for the brake assembly, and there is no plug on the PCB for the wire pigtail to the brake. If you examine the OP's photo with the PCB removed, it also lacks these features.

    I think the spindle brake must have been deleted in production at some point. Perhaps the manual wasn't updated to reflect the deletion, or the version on Bitsavers is not the latest.

  4. #14

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    Quote Originally Posted by Stone View Post
    After 20 some years of continuous (cold) storage I would think stiction is a likely suspect.
    Based on the OP's description of the spindle moving a few mm in either direction then resisting, I think this is the most likely situation. The heads are mounted on springy sheet metal arms that will twist/flex slightly if the head is stuck or dragging (ask me how I know...), which would cause the spindle to exhibit this behavior.

  5. #15
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    Quote Originally Posted by Chuck(G) View Post
    All ST-412s have a spindle brake (see the OEM manual on Bitsavers--it's prominently mentioned).
    The product manual two years later omits mention of a brake on the motor assembly. I too have never seen both Seagate OEM and Apple ProFile assemblies fitted with a mechanical brake, or even a regenerative braking system.
    = Excellent space heater

  6. #16
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    Hmm, interesting. The ST412s that I had were pretty early then.

  7. #17
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    Yes, it appears that there were variations of the ST-412.

    On page 36 (PDF page 44) of the manual at [here] is, "Spindle Brake (models with Motor Control PCB 20099)". Motor Control PCB 20099 is shown on page 47 (PDF page 55). The spindle brake is shown as item 13 on page 41 (PDF page 49), drawn as sitting beside the spindle grounding bar.

    For my ST-412, the 'Motor Control PCB' is labelled 'ASSY 20217'. It is the same shape as PCB 20099, but the component layout is very different. It is very close to, but not identical to the PCB 20136 board shown on page 48 (PDF page 56). And, missing is the shown spindle brake.

  8. #18
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    Okay, if the problem is stiction and the spindle does not want to rotate and there's no brake, you're likely to rip the heads right off the arms if you try to force things. Sometimes a smart rap on the side of the HDA with the handle of a large screwdriver can free things. Go much beyond this and you'll likely fatally damage things.
    Last edited by Chuck(G); December 10th, 2019 at 08:51 PM.

  9. #19

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    Please don't turn the spindle backwards. These heads have a sharp back edge. It will dig into the media and damage it. Try powering up and smacking it on the side with a screw driver handle as Chuck mentioned. If you don't know which direction it is suppose to rotate, don't force it. The brakes on these are not strong enough to keep you from rotating it. they are only suppos to slow it and keep it from rotating during transport.
    Dwight

  10. #20

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    Good morning,
    and thanks everyone for your comments on this problem!

    Last night, before I got more comments, I went back to the drive.
    I noticed, that i can wiggle the spindle back and forth 2-3 centimeters or about 1 inch.
    This encouraged me to keep wiggling it *gently*. After a while, the drive would move 2
    inches back and forth. Now that I've seen Dwights comment, I worry, that I might have
    damaged the disc surface or the heads. But that's what I did to it.

    I kept wiggling it, until I got it to turn full circle, clockwise. Wiggled some more for several
    minutes and got it to spin by fingers. Kept rotating the spindle for several minutes - clockwise.
    There was still some resistance, but I was not able to spin the spindle continuously with my fingers.

    I believed, that I could try to give power to the drive now and see, if it would run. Made a video
    of my attempt:
    https://youtu.be/3FFfZhQatSI

    I powered it up, after assembling the pcb. At first I thought, that it did started to spin, but
    I quickly realized, that it is only the atx power fan giving low noise. Spindle did not run on the drive itself.

    I then opened the pcb from one side, so that I could turn the spindle with my finger at the same time, when
    I would give power. When I powered up the drive, I could see, that the spindle moved for about half an inch.
    But that was all.

    I continued to help the spindle with my finger. I would give it a nice push, that made the spindle turn half a circle.
    It seemed obvious to me, that the spindle motor has not sufficient power to turn the spindle, no matter how much
    I try to help it. It occured to me, that the spindle motor must have had it and it is junk.

    But I kept playing with it for 5 to 10 minutes, just for my own fun. Kept kicking the spindle with my finger with power on.
    Spindle would rotate one or two full cirlces depending on strength of my push, but that was it. Just out of curiosity,
    I kept playing with it - not really believing that it would come alive.

    But then, I thought I would give it one more good push. and I saw it rotate maybe ten times! it was really trying to
    get back alive. On a second big push, it actually did! I realized, it may come alive and quickly got my phone to record
    and did catch the moment on the video, when the drive came alive for the fist time in decades .

    Well - alive and alive. At least the spindle is spinnig, but I realize, that I may have damaged the drive getting it this far.
    I should not get my hopes up just yet. There is no telling if the drive can hold data or read it. But it was 12pm for me,
    and I had to post pone trying it on the XT the next day. After work I can check what happens.

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