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help needed with Micro Expander Model 1

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    help needed with Micro Expander Model 1

    Hi all,

    i'm new to the whole S100 experience. My main hobby are Apple II computers but i had the wish to try something new

    I bought a rare S100 system, that should be compatible to the TRS80 or SOL computer. The unit has 2k of 2114 type Sram (4 chips) for memory (it seems) and is configured as a single board Computer with a additional S100 bus. There are several chip sockets not populated but that seems to be normal (). As the PSU was external and not included, i had so search a bit to get the Voltages right. It takes 8V DC and 2x 18?V AC to convert the AC voltages to +/-16V DC. There is a 12V and 5V voltage regulator inside the case. I infused the 8V and 16V into the voltage rails of the PSU-PCB and the computer seems to start. It draws 3A at +8V and 0.1A at +16V but the system does not 'boot'. I saved the monitor-ROM (D2732) and char-ROM (D2732) as files and copied them onto new ROMs but i got the same scrambled text display. I swapped the Z80 CPU with another one (measured 3.57 MHz at pin 6) but i got no change. The memory seemed to be ok as well...
    The text graphics on screen are 80x24 and are totally random (no change with or without CPU or Monitor)

    EDIT: The 64k memory board is a Central Data 64k

    I tried to contact Scott Ware from (http://www.corestack.com/machines/expander.html) but got no reply.

    If someone with a bit of knowledge about Z80 systems from the early 80s could help me?

    John Monahan has already pointed me to Debugging for beginners and thats what i will go through next.

    Micro_Expander_ROMs.zip

    BTW: i sent an email to Lee Felsenstein as well

    -Jonas
    Last edited by stynx; January 4, 2017, 01:43 PM.

    #2
    Scott Ware picked up that Micro Expander computer (free) in 1997,
    from a local computer store near Evanston, when he was at Northwestern University.

    The original Micro Expander computer was introduced at the West Coast Computer Faire in April 1981.
    The company was based in Chicago with Mats Ingemanson serving as president.

    Comment


      #3

      Last edited by stynx; January 5, 2017, 07:59 AM.

      Comment


        #4
        I have analyzed the memory board and it deactivates 6k of its memory from E800h to FFFFh. The first page of the ROM listing states that the ROM starts at F000h. This means there is 2k of memory (the onboard SRAM) from E800h to EFFFh.

        -Jonas

        Comment


          #5
          BigNick has sent me another pic
          Shipping to Germany will be a bit pricy, but still within my budget. Im very thankful to BigNick.

          Comment


            #6
            https://archive.org/details/EXP_MOD_1_Documentation

            Comment


              #7
              Originally posted by stynx View Post
              Hi all,

              i'm new to the whole S100 experience. My main hobby are Apple II computers but i had the wish to try something new

              I bought a rare S100 system, that should be compatible to the TRS80 or SOL computer....
              Hello Jonas,

              My neighbor passed away, his kids are clearing out his house, and we discovered two Micro-Expander computers. But we have no power supplies.

              Can you suggest where to look for a suitable power supply? Or do we need to make our own?

              Thank you very much in advance,

              stuart

              Comment


                #8
                Hello Stuart,

                I am Florian and get the Micro-Expander from Jonas.
                You find my whole story with it on my blog, micro-expander.funkenzupfer.de
                (Sorry, it's only in German, but I think Google translate it understandable.)

                I think you have to make the power supplies by your own.
                But it's not so difficult.
                When I remember correct you need a 8V DC and 15V AC.
                I can mount the Micro-Expander again and check this. But this would need some days.

                I am very interested on your Micro-Expanders. Can you make some photos?

                Florian

                Comment


                  #9
                  Originally posted by funkenzupfer View Post
                  Hello Stuart,

                  I am Florian and get the Micro-Expander from Jonas.
                  You find my whole story with it on my blog, micro-expander.funkenzupfer.de
                  (Sorry, it's only in German, but I think Google translate it understandable.)

                  I think you have to make the power supplies by your own.
                  But it's not so difficult.
                  When I remember correct you need a 8V DC and 15V AC.
                  I can mount the Micro-Expander again and check this. But this would need some days.

                  I am very interested on your Micro-Expanders. Can you make some photos?

                  Florian
                  The Micro-Expanders aren't mine; they belong to the heirs (adult children) of my deceased neighbor. He lived two doors away from me, so the M-E computers are nearby, but locked inside his house. Currently, nobody lives there, and I have no key. The next time the heirs visit, I'll try to slip in and get some pictures.

                  Please don't apologize for writing in your native language. There's an old joke about this:

                  If a person knows three languages, they're tri-lingual.
                  If a person knows two languages, they're bi-lingual.
                  If a person knows one language, they're mono-^H^H^H^H^H, um, American.

                  I do recall that one M-E keyboard was complete, and the other might have been missing one keycap. Neither machine has any S-100 cards installed. Both are reasonably clean and un-damaged (no obvious scratches &etc.).

                  I would be very grateful for any specifications for building a M-E power supply; ideally with pin-assignments. (If the inputs are clearly marked on the motherboards, I suppose I could figure it out myself... but I haven't disassembled one yet.) Thank you very much for the information about the necessary voltages; I'm surprised the M-E wants 15VAC. Take your time researching this; I greatly appreciate your efforts.

                  Thank you,

                  stuart

                  Comment


                    #10
                    micro-expander pictures

                    Originally posted by funkenzupfer View Post
                    Hello Stuart,

                    I am Florian and get the Micro-Expander from Jonas.
                    You find my whole story with it on my blog, micro-expander.funkenzupfer.de
                    (Sorry, it's only in German, but I think Google translate it understandable.)

                    I think you have to make the power supplies by your own.
                    But it's not so difficult.
                    When I remember correct you need a 8V DC and 15V AC.
                    I can mount the Micro-Expander again and check this. But this would need some days.

                    I am very interested on your Micro-Expanders. Can you make some photos?

                    Florian
                    We found one power supply. Here are some pictures.

                    IMG_20190630_185017.jpgIMG_20190630_185554.jpgIMG_20190630_190332.jpgIMG_20190630_190354.jpg

                    One machine seems to have a RAM card; the other has a RAM card and a floppy disk controller. We haven't tried powering anything up.

                    stuart

                    Comment


                      #11
                      That are good news.

                      If possible, please can you make some photos of S100 cards? Specially of the floppy controller.

                      I am still interested on the Expanders. Can you make a contact to the heirs? Or please ask them what they want to do with them.
                      Thanks a lot

                      Florian

                      Comment


                        #12
                        Originally posted by funkenzupfer View Post
                        That are good news.

                        If possible, please can you make some photos of S100 cards? Specially of the floppy controller.

                        I am still interested on the Expanders. Can you make a contact to the heirs? Or please ask them what they want to do with them.
                        Thanks a lot

                        Florian
                        The heirs have been absent for a while; daily temperatures here have routinely exceeded 38C (Sacramento, California). But the weather is cooling off again, and I saw the son a few days ago... I haven't been inside the house in months. I'll try to get more pictures when I can.

                        Sorry for the lack of progress,

                        stuart

                        Comment


                          #13
                          Originally posted by Stuart Hastings View Post
                          The heirs have been absent for a while; daily temperatures here have routinely exceeded 38C (Sacramento, California). But the weather is cooling off again, and I saw the son a few days ago... I haven't been inside the house in months. I'll try to get more pictures when I can.

                          Sorry for the lack of progress,

                          stuart
                          Hi Stuart

                          thanks for your reply.

                          The time is not a problem. The computer is more than 35 years old...

                          In Germany we had also over 40C the highest temperatures since weather recording.

                          I am patience
                          Florian

                          Comment


                            #14
                            I regret not grabbing a MicroExpander when they were available recently on ebay. Think I've seen 3 of them there. Hoping more come up. Not sure what you can do with one, but cool as a piece of Lee Felsentein memorabilia.

                            Comment


                              #15
                              As soon as I looked at the Microexpander pcb I thought it looked a lot like a SOL-20. And it has the same designer Lee Felsenstein so not a wonder they look similar. Here is a good report about it and interesting story, 200 units made and not paid for:

                              http://www.corestack.com/machines/expander.html

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