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  1. . I see in the service manual...

    .
    I see in the service manual for the HX-12, "Power Supply: 120V, 60Hz (220/240V, 50Hz available)".


    Good information. Based on my understanding of the information there, which may agree with...
  2. According to [here...

    According to [here], only a "very small percentage of equipment" is affected. Maybe a forum member who is an electrical engineer, might comment.
  3. The diagram is from the March 30, 1987, issue of...

    The diagram is from the March 30, 1987, issue of INFOWORLD magazine.
    If the Wikipedia article on the 5140 (IBM PC Convertible) is to believed, the 5140 was still being sold four years later (1991).
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    It has been established that the OP's ST-412 and...

    It has been established that the OP's ST-412 and my ST-412 do not have a physical spindle brake. That infers that the engineers of our drives were not concerned about platter rotation, in either...
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    Yes, it appears that there were variations of the...

    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...
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    In case of use for anyone later, I have been able...

    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...
  7. For the 5160's PSU, the 130W rating is in regards...

    For the 5160's PSU, the 130W rating is in regards to the DC output voltages (per [here]), i.e. excludes the auxiliary power output.


    A step-down transformer modifies voltage only. The frequency...
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    That thing grounds the spindle. During this time...

    That thing grounds the spindle. During this time of diagnosis, it can be removed.


    I see no braking mechanism.


    Confirm for us that the 5 mm is at the outer edge of the spindle.

    If that...
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    My ST-412 does not have a spindle brake. On your...

    My ST-412 does not have a spindle brake.
    On your ST-412, do you see anything extra (mechanical that is) to what is shown in the photo at [here] ?


    I do not know why that would be so.

    On my...
  10. No. For example, the power supply in the IBM...

    No.

    For example, the power supply in the IBM PCjr does not generate a POWER GOOD signal (or equivalent). Instead, motherboard reset at power-on time is controlled by a capacitor/resistor/diode...
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    Welcome to these forums. Yes. The spindle...

    Welcome to these forums.


    Yes. The spindle noise of an ST-412 is very noticeable. And if you put your hand on the top of the drive, you can feel vibration.

    My ST-412's spindle turns when only...
  12. Yes. Do you know if your motherboard...

    Yes.


    Do you know if your motherboard requires a POWER GOOD signal (or equivalent) from the PSU? In most AT-class motherboards, the motherboard requires the POWER GOOD signal to go high in order...
  13. Your second post has appeared. Looking at...

    Your second post has appeared.


    Looking at the datasheet, from an electrical perspective, I cannot see why not. There is though, a remote possibility that the code in the 8041 is not suitable for...
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    You already have items 4 and 6 ?

    You already have items 4 and 6 ?
  15. Different make-model of drive, but supports...

    Different make-model of drive, but supports suggestions of some earlier posts:

    * The thread at [here] is about a YD-380 drive 'making very strange sounds' due to lack a terminator.

    * In one of...
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    So that readers are clear about what exactly you...

    So that readers are clear about what exactly you mean by "faceplate":
    Refer to page 7 of the IBM document at [here]. Which number, or numbers, are you seeking ?
  17. Welcome to these forums. With the majority...

    Welcome to these forums.


    With the majority of AT-class keyboards that I have tried it on, simply connecting power only to the keyboard, results in the keyboard's LED's flashing on momentarily....
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    S1 and S2 is the secondary of the power...

    S1 and S2 is the secondary of the power transformer. The SAMS circuit diagram of the power supply, at [here], shows that when your 5151 is working, you should be measuring about 22 Vac. Did you have...
  19. I have hosted the files at [here...

    I have hosted the files at [here], in the Datel section.

    Within the PDF of the instruction manual, I performed OCR (which also de-skewed pages), and I added bookmarks.
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    Regarding symptom #1. It sounds like the...

    Regarding symptom #1.

    It sounds like the symptom is triggered by heat: When the symptom appears, the symptom 'cause' cools down, and everything starts working again. A constant cycle of on and...
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    I see two symptoms, with different causes: #1....

    I see two symptoms, with different causes:
    #1. 5151 shutting down.
    #2. Unexpectedly seeing only a blinking cursor when the 5151 is moved to a computer that is known to display a RAM count-up.
    ...
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    NOTE: Below is for IBM DOS 3.3 - other...

    NOTE: Below is for IBM DOS 3.3 - other makes/versions may have different behavior.

    1. I brought out my IBM XT, which is fitted with a 20MB 'MFM' hard drive.
    2. I then high-level formatted the...
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    It is MFM.

    It is MFM.
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    If one starts Speed Disk, then chooses not to...

    If one starts Speed Disk, then chooses not to perform the optimise operation, then Speed Disk shows the current block map (distribution of used and unused cluster blocks).
    One can then exit to DOS,...
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    That is not how I am seeing IBM DOS 3.3 behaving...

    That is not how I am seeing IBM DOS 3.3 behaving (as observed via the 'block' map in Norton Speed Disk).

    I expect that over the years, Microsoft adjusted the cluster allocation algorithm. In the...
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