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  1. Replies
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    Or, I am a slower typist than you, but had less...

    Or, I am a slower typist than you, but had less to type.

    More patch wire examples at [here].
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    At [here...

    At [here] is an earlier thread on the subject.
  3. At [here...

    At [here] is pictured one that failed (open circuit) on me some years ago.
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    There is a kit for a logic probe shown at [here...

    There is a kit for a logic probe shown at [here]. That probe does no sampling.
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    I think "sampling" is the wrong word to use for a...

    I think "sampling" is the wrong word to use for a logic probe.
    But yes, the 2 MHz quoted for your logic probe is a limit. Beyond that, alternating digital signals may not be expected to show as...
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    I have never needed to do the action. But post...

    I have never needed to do the action.
    But post #3 at [here] is an example of someone doing it.
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    'V ADJ' potentiometer (RT1). In the SAMS...

    'V ADJ' potentiometer (RT1).
    In the SAMS document, read the first block on the 'Miscellaneous Adjustments' page.
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    For the TM100-2A, some people have reported...

    For the TM100-2A, some people have reported fixing a seized/partially-seized stepper by putting WD-40 into the stepper.
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    Quote: "not quite the same". Explain, ideally...

    Quote: "not quite the same". Explain, ideally with examples. And SAMS would have made their measurements under load, and so that should be the basis of the comparison.



    The fact that you asked...
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    War story: Many many moons ago, a fellow...

    War story:

    Many many moons ago, a fellow technician left the workshop that I was a member of, and transferred to me was a dismantled EGA monitor (including a tray of parts [screws, etc.]) that the...
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    Yes, various possibilities. For example, at [here...

    Yes, various possibilities. For example, at [here] is described a 5150 that was displaying 201/301/131 errors, and the cause turned out to be a RAM card.
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    Yes, but you wrote, "Because 301 means faulty...

    Yes, but you wrote, "Because 301 means faulty keyboard anyway.", an incorrect/misleading statement. If not pointed out, some readers (now and later) will learn incorrect information. And sometimes...
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    In an IBM 5160, the 301 error means that the...

    In an IBM 5160, the 301 error means that the keyboard test failed.
    Certain failure modes of the keyboard interface circuitry on the 5160 motherboard can result in a 301 error.
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    Welcome to these forums. Rather than...

    Welcome to these forums.


    Rather than writing, "The PC", it is better to use, "The XT", otherwise some people will get confused, thinking you have an IBM PC.


    There is lots of IBM XT (IBM...
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    Only 8 channels. That is quite limiting. Okay...

    Only 8 channels. That is quite limiting.

    Okay for for something like [this], where only 4 channels are needed (POWER GOOD, PA0, PA1, PA2).

    But, for example, what if you wanted to monitor the...
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    A logic analyzer. Again, like any test equipment,...

    A logic analyzer. Again, like any test equipment, you will need to gain the knowledge of how to use it. You have a functioning 5160 motherboard and so you can use that for learning, and to see what...
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    For the IBM 5160, the sequence of events that...

    For the IBM 5160, the sequence of events that occurs before the POST starts is shown at [here]. To verify that ALL of that is happening, you would need a range of different test equipment (and the...
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    I did that, and as expected, I saw a RAM count-up...

    I did that, and as expected, I saw a RAM count-up on the screen. So you can rule out a faulty BIOS ROM chip as the problem cause.


    The 8255A would have to be faulty in a way that interferes with...
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    See post #22 at [here...

    See post #22 at [here].
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    It is informing you that either: * The POST is...

    It is informing you that either:
    * The POST is not starting, or
    * The POST is starting, but not getting as far as step 13.


    Yes, but that will not inform you of what caused the halt, or when...
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    The link shows the 8284A generating the 4.77 MHz...

    The link shows the 8284A generating the 4.77 MHz clock, with the "CPU, 8288, NPU" receiving that clock.

    (The NPU {8087} socket does not need to be checked. The NPU, if present, is not involved in...
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    The people/companies at [here...

    The people/companies at [here] can create the ROM for you.
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    Quite a few posts have appeared. For...

    Quite a few posts have appeared.


    For readers, the T1100 maintenance manual indicates that the 80C49 is in fact being used as a keyboard controller.


    On my good T1100, I hear a single beep at...
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    A faulty BIOS ROM is a possibility, so try a BIOS...

    A faulty BIOS ROM is a possibility, so try a BIOS ROM from another 5160.


    Your logic probe should show alternating signals, such as clocks.
    Use it to see how it behaves when measuring the 4.77...
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    Based on the symbol, the chip maker is Siemens...

    Based on the symbol, the chip maker is Siemens (see [here]).
    A search for "Siemens 8493286" shows some hits, some including "DIP16", and so I suspect that 8493286 is the part number.

    Siemens'...
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