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  1. Replies
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    Lots of IBM 5150 information at...

    Lots of IBM 5150 information at minuszerodegrees.net


    Careful. The IBM 5151 can be damaged if it is plugged into the wrong type of video card.


    Photo #1: The 16KB-64KB type of 5150...
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    Out of interest, is it one that you have just...

    Out of interest, is it one that you have just acquired, or one that was working for you but no longer working ?
    If the previous, it opens up other possibilities, e.g. wrong type of SIMMs fitted by a...
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    I have made an assumption (shame on me) that you...

    I have made an assumption (shame on me) that you are dealing with two problems, a power supply problem and a motherboard problem.

    If we go back to your original question, with the subject being a...
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    In theory, there is a timing consideration. In...

    In theory, there is a timing consideration.

    In many motherboard designs, after power-on, the motherboard is held in the reset state for a short period. One of reasons may be the 8088. Its...
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    Damage could result through over-voltage. For...

    Damage could result through over-voltage. For example, the power supply generating +6V on the +5V line.

    I expect that a decent power supply will contain circuitry to detect an over-voltage...
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    Some EU based services are included at [here...

    Some EU based services are included at [here].
  7. Replies
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    The fact that your multimeter is beeping,...

    The fact that your multimeter is beeping, suggests to me that you have your multimeter in the 'continuity' setting. For future reference, note that the continuity setting can sometimes be...
  8. They appear in the results of an eBay search...

    They appear in the results of an eBay search using: laptop post tester
  9. Are you are aware that [these...

    Are you are aware that [these] are available on eBay ?
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    I panicked when I thermally observed the same...

    I panicked when I thermally observed the same with my cat, Jenny, but the cause turned out to be that she is very analytical/logical, i.e. very left brained. :-)
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    Random 0400 201 For the '64KB - 256KB' type of...

    Random 0400 201

    For the '64KB - 256KB' type of 5150 motherboard, the '04' in '0400 201' corresponds to address 16K, i.e. an address within RAM bank 0.
    I do not know how an 'uncabled' extender...
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    In the 'optional Boot ROM' of the diagram is a...

    In the 'optional Boot ROM' of the diagram is a note that includes, "RP2 always required, or 10K resistor between pins 1-2".

    Yes, the diagram would have been 'cleaner' if RP1 had been used instead,...
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    Maybe the ET4000 based card is faulty, faulty in...

    Maybe the ET4000 based card is faulty, faulty in a way that makes its I/O ports appear at multiple areas, with one of those areas being the same area used by the CMOS/RTC chip.
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    And does the error message reappear if you put...

    And does the error message reappear if you put back the original video card ?
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    So, 'CMOS inoperational SYSTEM HALTED' always...

    So, 'CMOS inoperational SYSTEM HALTED' always appearing at power on.
    That certainly sounds like the POST's test of the 'CMOS/RTC' chip (per [here]) is failing.


    Had the subject been an IBM 5170...
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    In my experience, resistor arrays are very...

    In my experience, resistor arrays are very reliable.

    Have you ruled out the power supply as the cause ?

    If yes, do you see 4.28V when the motherboard is the only device powered by the power...
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    To me, that is lower than expected. For example,...

    To me, that is lower than expected. For example, looking at the data sheets of the RAM at [here], 4.5V is usually the minimum. What does the data sheet for your fitted RAM indicate?
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    IBM PC ? If so, confirm for us that it has the...

    IBM PC ?
    If so, confirm for us that it has the the third and final motherboard BIOS revision (10/27/82).


    How do you know that?
    An 1801 error on-screen when the 5161 is disconnected?


    1....
  19. Replies
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    Yes, as measured by oscilloscope. There is...

    Yes, as measured by oscilloscope.


    There is no 8284 on my board.


    On my board, the CLOCK pin (pin B20) of the ISA connectors is connected to the CLK pin (pin 19) on the V20, which in turn, is...
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    In the manual that dkedrowitsch pointed to, the...

    In the manual that dkedrowitsch pointed to, the front page is titled 'UX Turbo (44256 VERSION)'. 44256 is the main type of RAM chip on my motherboard. Because your board uses 414256 RAM instead,...
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    I have updated that entry to reflect the...

    I have updated that entry to reflect the information learned in this thread.
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    At [here...

    At [here] is a lot of Displaywriter documentation.

    One of the documents there is named S241-6248-3_Displaywriter_Product_Support_Manual_Feb83.pdf, and its chapter 9 covers diagnostics.
    Have you...
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    "echo ^G" alone is enough. Not sure why I added...

    "echo ^G" alone is enough.
    Not sure why I added the redirection to the console.
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    Of course, the symptoms may be totally unrelated....

    Of course, the symptoms may be totally unrelated.


    Nil video symptom

    Could even be the monitor. Try another monitor.

    Does the symptom appear using a different video card.

    Symptom onset...
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    Thanks to Chuck, EzTape version 1.13 is now...

    Thanks to Chuck, EzTape version 1.13 is now hosted at [here] (under 'Irwin').
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