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Thread: National Semiconductor SC/MP Introkit

  1. #11
    Join Date
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    So,

    My first questions are:

    1. What markings are on the 3-pin voltage regulator by the CPU? It should be something like 79xx. The 9 would indicate it is a negative voltage regulator and the xx is the voltage it regulates to. From the images I can just about make out 7906. Is that correct?

    2. Are the three pins of the voltage regulator actually soldered together on the underside of the printed circuit board (PCB) or not?

    3. What are the markings on the cylindrical component where the crystal should be soldered into?

    Dave

  2. #12

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    I visited TNMOC at Bletchley a little over a month ago and took several photos of the National Introkit in the glass case, although it was surrounded by other things and not well lit which made getting a clear shot difficult. Away from base just now, I will dig out those photos and post them here if there is any readable detail in them.

    Oh, and I also took at least one photo of another example at The Centre For Computing History (Near Cambridge) one day later. I'll dig that / those out as well.
    Last edited by SiriusHardware; September 1st, 2019 at 01:58 AM.

  3. #13

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    Just been sifting around a little bit more:-

    I went to the Centre For Computing History's website hoping to find their own images of their Introkit, but the website is a little bit out of date because the Introkit is only recorded there as being part of the contents of a box of miscellaneous boards. However, as of July '19' that was not true as it was out on display in a case next to an Acorn System 1.

    But, I did find this other Introkit related item in their documents library.

    http://www.computinghistory.org.uk/d...-User-s-Manual

    From recent experience I know that the museum's policy regarding documents / magazines is not to put them online, presumably so that they do not incur the wrath of rights holders - but - I know that if you write / email them and ask for a copy of any specific document or article they will usually let you have a copy provided you sign a form agreeing that it is for personal use only and agree -not- to distribute copies.

    Although it relates specifically to the keyboard kit, it may be worth obtaining a copy of this document from the museum to see if it contains any Introkit related information not available anywhere else.

  4. #14

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    Quote Originally Posted by daver2 View Post
    The other cards are (presumably) part of something else that the previous guy was building.
    Except this one: https://imgur.com/1gHq5tG
    It's look like an original extension board.

    Quote Originally Posted by daver2 View Post
    I suspect that some of the cards plugged into the 3-way backplane I can see.
    Yes, probably used for that. (See previous photo - SC/MP Application card)

    Quote Originally Posted by daver2 View Post
    Can you let me know what test equipment (if any) you have...
    Currently I only have a multimeter, but I am willing to buy anything else so that I can fix it.

    Quote Originally Posted by daver2 View Post
    ... whether you have any electronic experience at all
    Sometimes I repair old computers, cash registers, etc., but my electronics skills are at average level.

  5. #15

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    Quote Originally Posted by daver2 View Post
    Looks like the crystal has been replaced with a capacitor?
    Yes, it looks like.

    Quote Originally Posted by daver2 View Post
    Also not sure why someone has put Green LED's in place of the capacitor either on the Bletchley PCB!
    I don't think that's a LED. It has an inscription on it.
    It looks like a ceramic capacitor. (Something like this: https://images-na.ssl-images-amazon....1V76fzhijL.jpg )

    Quote Originally Posted by daver2 View Post
    Good, please don't power the unit up until we are certain what we are dealing with...
    As I said earlier, I want to do more research before I do anything.

  6. #16

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    Quote Originally Posted by daver2 View Post
    1. What markings are on the 3-pin voltage regulator by the CPU?
    The markings on the voltage regulator: UA7906 UC7935.

    Quote Originally Posted by daver2 View Post
    2. Are the three pins of the voltage regulator actually soldered together on the underside of the printed circuit board (PCB) or not?
    No, they are not soldered together.

    Quote Originally Posted by daver2 View Post
    3. What are the markings on the cylindrical component where the crystal should be soldered into?
    K680

  7. #17

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    Quote Originally Posted by SiriusHardware View Post
    I will dig out those photos and post them here if there is any readable detail in them.
    Quote Originally Posted by SiriusHardware View Post
    I'll dig that / those out as well.
    Thank you for any help you can offer.

    Quote Originally Posted by SiriusHardware View Post
    I know that if you write / email them and ask for a copy of any specific document or article they will usually let you have a copy provided you sign a form agreeing that it is for personal use only and agree -not- to distribute copies.
    I wrote a letter to them and I hope they help with the this.

  8. #18

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    As I mentioned earlier, I wrote a letter to Curious Marc.
    He scanned all the documents (and other things like, binary dumps) and he had and share with everyone in his website.
    Here is the link: https://www.curiousmarc.com/computing/scmp

    If everyone allowed it, I'll upload it later all the collected documentation to archive.org.

  9. #19

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    To my consternation, I can't find any images of the Introkit at TCFCH (Cambridge) - I did find quite a few of the one at TNMOC but I'm not sure they will furnish anything more useful than the original photo - the vast majority were duplicates as I battled to keep my hands steady enough to get the pictures sharp in the low light.

    The first attached image shows that TNMOC (Bletchley) actually have two Introkits, one of them unbuilt and still in the original packing. What's interesting is that even between these two the PCB layout of the components of the basic Introkit, without any keypad / display components added, is quite different. The second image is a closer view of the built one which the OP linked to in his second post, so I would surmise that on this one the additional components on the perforated board area are those which are added when the keypad and display are added to the system.

    This raises the question, how could you do anything with the basic introkit which didn't have a keypad or display? On the right hand side of the black backing card of the unbuilt kit the 7414 IC (which is a hex schmitt trigger inverter) is described as the 'Teletype Interface', so I guess communication with the basic Introkit may have been via a Teletype / terminal.

    Dave, those 'green LEDs' which have replaced two of the capacitors on the built machine are actually Tantalum Bead capacitors (an unusual colour for them, I must agree).
    Attached Images Attached Images

  10. #20
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    Now we've got a better photograph it is obvious they are tantalum bead capacitors! Good spot...

    Yes, the 'original' introkit had a KITBUG monitor and a teletype interface. The hex keypad interface and the modified monitor came along later. As I understand it, the MK14 '-' monitor is the same as the NS variant for use with the introkit and the hex keypad interface.

    I am at Cambridge at the weekend so I will see what I can acquire in the form of documentation.

    Dave

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