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  1. Replies
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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...
  2. 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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    But maybe the POST in that 386 does not try to...

    But maybe the POST in that 386 does not try to read the last track. The POST authors do not need to copy IBM.

    And DOS is probably not going to write/read that track until the drive has been almost...
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    It does. See the 'Modern power supplies' section...

    It does.
    See the 'Modern power supplies' section at [here].
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    Imagine that sometimes, at 5150 power on, the...

    Imagine that sometimes, at 5150 power on, the spindle motor in the drive is unable to overcome 'head stiction' to spin the platter. If that possibility is what is happening, then perhaps you can...
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    The photos at [here...

    The photos at [here] show how close the IBM Graphics Memory Expansion Card comes to the adjacent card in an IBM 5170.
    Clearly, that is why the IBM Graphics Memory Expansion Card has a protective...
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    "1701" is generated by the BIOS expansion ROM on...

    "1701" is generated by the BIOS expansion ROM on the Plus Hardcard (and other XT-class hard disk controllers). Part of the code in that ROM gets executed at computer startup time. Unfortunately, 1701...
  14. There were many different models. I suggest that...

    There were many different models. I suggest that you should avoid any for which you cannot locate switch/jumper setting information. Manuals for two are at [here].


    There is an earlier related...
  15. Replies
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    Yes, under the large and medium sized aluminium...

    Yes, under the large and medium sized aluminium electrolytic capacitors is glue.



    Line suppression capacitors are supplied in various forms. In your PSU, some of the brown/blue capacitors may...
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    Got it. Where in the PDF, it shows "12.70", I...

    Got it.

    Where in the PDF, it shows "12.70", I measure 13 mm, so close enough there.

    However, the two holes in the IBM EGA card are 4 mm diameter.
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    I receive a HTTP 404 error for that link. I...

    I receive a HTTP 404 error for that link.


    I will get back to you on that; I have a few things to do now.
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    I have a fully functional IBM 5170, fitted with a...

    I have a fully functional IBM 5170, fitted with a type 2 drive, an ST-4026. If I change the hard drive type number in SETUP from 2 to 3, then restart the computer, I see (after a minute or so) a 1790...
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    The thread at [here...

    The thread at [here] appears to show a matching motherboard connector. If it is a mtach, the thread suggests a PSU for the Compaq Presario. The label on the (HIPRO) PSU pictured there shows no -5V...
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    Note that if the replacement PSU does not...

    Note that if the replacement PSU does not generate -5V, then it will be a problem for the IBM 5150. See the 'Modern power supplies' section at [here].
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    See [here...

    See [here].

    Hole diameter is 4 mm.
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    1780 or 1790 ?

    1780 or 1790 ?
  23. Replies
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    Broken off, or not present ? For example: *...

    Broken off, or not present ?

    For example:
    * MDA does not use pins 3, 4, and 5. In the 9-pin connector of my IBM MDA monitor (IBM 5151), those pins are not present.
    * CGA does not use pin 7. In...
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    A warning, from [here...

    A warning, from [here]:

    Aged tantalum capacitors are known to explode. That has happened to me many times, particularly when I have acquired something that has not been powered on in years. If...
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    Provide a photo of it. A possibility: The...

    Provide a photo of it.


    A possibility:

    The 5150's PSU contains a few line suppression capacitors. Sometimes, one ruptures, releasing smoke and odour.
    This often confuses people, because the...
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