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Replica Science of Cambridge MK14 available for pre-order.

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    Replica Science of Cambridge MK14 available for pre-order.

    A PCB (plus assorted items) to construct a Science of Cambridge MK14 is available from Martin Lukasek to pre-order.

    His e-mail address is martin.lukasek@artax.cz and his website is http://www.8bity.cz/2018/final-repli...mk14-sinclair/.

    For those not versed in the Czech language (me included) there is an assortment of flags to help out with the understanding!

    He also has a PCB for the VDU (not released yet). Watch this space...

    A much cheaper option than buying one off a certain auction site !

    I have just put a pre-order in.

    Pre-programmed ROMS are also available (with either version 1 or 2 of the SCIOS), as is the 'nasty' keyboard (for authenticity)...

    Dave

    #2
    One of the very few kits that used the NS SC/MP, a strange beast for the time.

    Are MPUs still kicking around as parts?

    Comment


      #3
      Yep.

      A company in the U.K. (Langrex) Has 7 NOS devices on their shelves. I bought 2 from them a while ago. What I am having trouble finding is the I/O RAM chip (INS8154). Must redouble my efforts to find a couple of these...

      Dave

      Comment


        #4
        Originally posted by daver2 View Post
        Yep.

        A company in the U.K. (Langrex) Has 7 NOS devices on their shelves. I bought 2 from them a while ago. What I am having trouble finding is the I/O RAM chip (INS8154). Must redouble my efforts to find a couple of these...

        Dave
        I see a bunch on the US Ebay site.. https://www.ebay.com/sch/i.html?_fro...S8154&_sacat=0

        Comment


          #5
          The 'authentic' keypad looks as though it uses metal-dome contact switches like the late issue MK14 / late version of the original MK14 keypad. As such, it won't be nearly as bad as the early 'conductive rubber sheet' version.

          What would be nice would be if someone would make a self contained stick-down modern membrane 'sandwich' version of the keypad with a flying ribbon cable going out to the right with a 12-way 0.1" connector on it. It could then be retrofitted to any original MK14 with a faulty keypad or with the keypad missing altogether. It's been done already for the ZX81 and Spectrum, but there probably aren't enough qualifying MK14s to make producing an MK14 membrane keypad worth anyone's while.

          Comment


            #6
            There is now a completed, fully populated example of one of these replicas up for sale. The seller (possibly the same individual who made these boards available) is making it very clear it is a replica. Not unreasonably priced compared to a real MK14 in as-new condition.

            https://www.ebay.co.uk/itm/Science-o...item33e56e381e

            There's also someone else selling MK14 PCBs which are made in the modern style, green, with solder resist and laid out to use keyswitches only.

            https://www.ebay.co.uk/itm/Science-o...item1a47e54fe6

            Comment


              #7
              I was looking at that replica... pretty impressive. I'm amazed at how rare the originals are.. I thought there were thousands produced.

              I'm not buying any though. I am finally taking Chuck's advice and spending my budget this month on a scope.

              Comment


                #8
                Wow! It's at $405 already!!

                Comment


                  #9
                  Pretty steep price indeed. Can't see an estimated price in Martin's page, is it about the same?

                  Comment


                    #10
                    >>> There's also someone else selling MK14 PCBs which are made in the modern style, green, with solder resist and laid out to use keyswitches only.

                    They have a none e-bay presence as well (same price though) at http://jmprecision.co.uk/shopping/st...=1&cat=17&=SID.

                    I bought one of his bare MK14 PCBs and I am almost finished populating it. Just got to resolve a few supply items.

                    I had an e-mail chat with the guy at J M Precision and he has lots of other potentially interesting PCBs in the pipeline... I feel a few more construction projects in the near future...

                    Dave

                    Comment


                      #11
                      Originally posted by falter View Post
                      Wow! It's at $405 already!!
                      Um, when I said I thought it was reasonably priced compared to a nice original, that was based on my having seen it at about $100. I thought that was the fixed price. I didn't realise it was an auction.

                      Comment


                        #12
                        The auction is mine. I just wanted to try. As the price got higher than I expected I will add some aditions to the winning bid. I will possibly make few more, while some people are willing to pay, but not too many. I do not want to make money on it, I will be glad to cover some expenses.

                        The price about $100 is impossible, as just the cost of the parts is about $150, not including assembly work and eBay/PayPal fees. If anyone wants the PCB, keyboard, programmed PROMs and/or few other parts, just write me an e-mail, I sell them off eBay for almost production cost and I do not plan to make too many. These orgnizing/selling job is not hobby, not fun.

                        Comment


                          #13
                          Originally posted by Kiwisek View Post
                          The auction is mine. I just wanted to try.
                          There's no implied criticism of yourself or your beautifully made replica MK14 - I am just always astonished by what people will pay for original MK14s, some in very bad condition.

                          Your auction has proved, to the surprise of everyone even including yourself, I think, that there are people who will pay quite a lot to own an MK14 even when it is not an original 1977 machine. This is something I would not have guessed.

                          Could you tell us more about the keypad? I guess it is made to fit your PCB specifically, or would it fit and work on original MK14s from and above a certain issue? As you are obviously aware, often the main problem with original MK14s is the condition of, or the complete lack of, a keypad.

                          Comment


                            #14
                            The keyboard construction is described here http://www.8bity.cz/2018/tips-for-bu...-mk14-replica/. Sorry for the language, please use Google translate icon in upper right corner.

                            The keybaord is slightly different from the original. There were 3-legged domes and I user 4-legged ones because of availability. In otehr aspects it is similar, even the PCB layout is almost the same.

                            Comment


                              #15
                              Originally posted by Kiwisek View Post
                              The keyboard construction is described here http://www.8bity.cz/2018/tips-for-bu...-mk14-replica/. Sorry for the language, please use Google translate icon in upper right corner.

                              The keyboard is slightly different from the original. There were 3-legged domes and I user 4-legged ones because of availability. In otehr aspects it is similar, even the PCB layout is almost the same.
                              Thanks for the information.

                              I think your new keypad overlay could still be used to restore the keypad on an original late-issue MK14 but it would be necessary to find three-legged dome contacts - probably from a cheap late 1970s calculator.

                              I notice you are in the process of producing a replica MK14 VDU as well. The main problems with this add-on originally were

                              -It has no RAM of its own, and steals 512 bytes of the MK14's official maximum of 256+256+128 bytes of memory, leaving the MK14 very short of program memory.
                              -It halts the SC/MP whenever it is reading data from the 512 bytes of RAM used as video RAM, causing bad system slowdown.
                              -The 4.33MHz crystal originally fitted to the MK14 has to be changed to 4.00MHz. That upsets any critical software timing in any software originally written for a 4.33MHz clock.

                              Therefore, if you reproduce the VDU PCB I have a suggestion for another add-on project which will greatly improve it - a dual-port RAM PCB to go between the MK14 and the VDU PCB. With this, the VDU could read continually from the dual-port RAM without halting the SC/MP, and it would not tie up any of the MK14's own RAM. That would make the VDU much more usable. If the dual-port RAM PCB also included a dedicated 4MHz clock output to the VDU PCB, it would not be necessary to change the MK14 clock from 4.33MHz to 4.00MHz.

                              I own an original MK14 and original VDU PCB, so at one time I looked into doing this myself (just as a hobby project, not a finished PCB), and identified the IDT7130 chip as a possible basis for such a project:

                              https://www.idt.com/products/memory-...-dual-port-ram

                              I went so far as to buy the IC, but never got around to building the project.
                              Last edited by SiriusHardware; April 4, 2018, 09:24 AM.

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