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MITS cassette adapter hookup to the outside world

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  • corey986
    So I managed to get my hands on a MITS cassette adapter card set, it is a nice no-solder mask card set. It has the phono jacks attached to the cables. I wasn t
    Message 1 of 16 , Dec 20, 2013
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      So I managed to get my hands on a MITS cassette adapter card set, it is a nice no-solder mask card set. It has the phono jacks attached to the cables.

      I wasn't going to go the route of cassette since I have my paper tape setup, but with Mike adding a real cassette adapter to his replica setup I figure tapes may become more a popular way to load software.

      My question is how is it normally attached to the back of the Altair chassis so I can plug in external cables. I have the factory mesh over the cassette output ports currently and don't want to remove that. So any pics would be helpful. If however if was common practice in the early units not to mount jacks and simple hang the cables out a serial/parallel port hole I'd like to know that also, which may explain my cabling setup on this set. I do have one unused port that I can remove the db25 from.

      Thanks, Corey
    • wtsnet
      Here is link to an image of a 88-UIO cable: http://www.virtualaltair.com/virtualaltair.com/images/88-UIO%20cable%20-150.jpg
      Message 2 of 16 , Dec 20, 2013
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      • John Crane
        BTW, These things are easy to make. Grey cable from Radio Shack, white plug for I/O card pins from Mouser, part# 538-09-50-7101 and matching metal pins part #
        Message 3 of 16 , Dec 20, 2013
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          BTW,
          These things are easy to make.
          Grey cable from Radio Shack, white plug for I/O card pins from Mouser, part# 538-09-50-7101 and matching metal pins part # 538-08-56-0108

          -J
          --------------------------------------------
          On Fri, 12/20/13, yahoo@... <yahoo@...> wrote:

          Subject: [Altair Computer Club] RE: MITS cassette adapter hookup to the outside world
          To: altaircomputerclub@yahoogroups.com
          Date: Friday, December 20, 2013, 4:14 AM














          Here is link to an image of a 88-UIO cable:

          http://www.virtualaltair.com/virtualaltair.com/images/88-UIO%20cable%20-150.jpg


          W. Tom S.
        • wtsnet
          Does the 88-ACR cassette interface only work with the MITS 2400/1850 Hz frequencies? Is there a mod for KC Standard? I have MITS Tapes that are KC Standard.
          Message 4 of 16 , Dec 20, 2013
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            Does the 88-ACR cassette interface only work with the MITS 2400/1850 Hz frequencies? Is there a mod for KC Standard? I have MITS Tapes that are KC Standard. Are the tapes for the 88-UIO only or were the 88-ACR modem boards modified to KC frequencies.

            W. Tom S.
          • mfeberhard
            The standard 88-ACR frequencies are 2225 Hz for logic 1, and 2025 Hz for logic 0. (not 2400/1850 Hz.) See page 24 of the 88-ACR manual. As far as I know, the
            Message 5 of 16 , Dec 20, 2013
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              The "standard" 88-ACR frequencies are 2225 Hz for logic 1, and 2025 Hz for logic 0. (not 2400/1850 Hz.) See page 24 of the 88-ACR manual.

              As far as I know, the 88-ACR does not support the Kansas City standard. I believe the design actually predates the KC Standard...
              Martin E
            • wtsnet
              I believe you are correct that the 88-ACR predates the Kansas City standard. I have several MITS Kansas City Standard BASIC cassettes. I thought maybe there
              Message 6 of 16 , Dec 20, 2013
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                I believe you are correct that the 88-ACR predates the Kansas City standard. I have several MITS Kansas City Standard BASIC cassettes. I thought maybe there was a mod created after the manual.

                I'll find a manual to read. I read the labels on Altair 8K Basic and Altair Package II cassetes They both say 2400/1850 Hz
              • deramp5113
                The 88-ACR was originally designed to duplicate the Bell 103A standard frequencies of 2225Hz/2025Hz. However, because customers had so many problems with the
                Message 7 of 16 , Dec 20, 2013
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                  The 88-ACR was originally designed to duplicate the Bell 103A standard frequencies of 2225Hz/2025Hz. However, because customers had so many problems with the interchangeability of media, MITS changed the 88-ACR (as well as software distributed on cassette) to 2400Hz/1850Hz  in March of 1976. The same center frequency of 2125Hz was maintained.


                  Mie


                • wtsnet
                  Thanks Mike! That explains the differences in specifications on http://virtualaltair.com/virtualaltair.com/vac_88-ACR.asp.
                  Message 8 of 16 , Dec 20, 2013
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                    Thanks Mike! That explains the differences in specifications on http://virtualaltair.com/virtualaltair.com/vac_88-ACR.asp.

                    Does anyone a document or photo that shows the 88-ACR frequencies modifications. I have and 88-ACR and don't know what frequencies it uses. Several group members have this card. Are the cards commonly using the new frequencies or are they a mix?

                    W. Tim S.
                  • deramp5113
                    Tom, This issue of Computer Notes discusses the modification: http://altairclone.com/downloads/computer_notes/1977_02_11.pdf
                    Message 9 of 16 , Dec 20, 2013
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                      Tom,


                      This issue of "Computer Notes" discusses the modification: http://altairclone.com/downloads/computer_notes/1977_02_11.pdf


                      Mike


                    • wtsnet
                      Great! I m glad to see the 88-ACR is well documented. I ll add more PDF file links to my page and move the PDF Files to my server so I don t use you bandwidth.
                      Message 10 of 16 , Dec 20, 2013
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                        Great! I'm glad to see the 88-ACR is well documented. I'll add more PDF file links to my page and move the PDF Files to my server so I don't use you bandwidth.

                        I added images of my 88-ACR to the page: http://www.virtualaltair.com/virtualaltair.com/vac_88-ACR.asp.

                        The Technical Information sheet shows the cables, but not that clearly. Here is an image of the back panel mounting holes and labels:

                        http://www.virtualaltair.com/virtualaltair.com/images/88-ACR%20connector%20%20labels.JPG

                        The 88-UIO looks more appropriate for an 8800b. I'll put this 88-ACR on eBay and use an 88-UIO.

                        http://www.virtualaltair.com/virtualaltair.com/images/88-ACR%20Modem-150.jpg
                        http://www.virtualaltair.com/virtualaltair.com/images/88-ACR%20SIOB-150.jpg
                        http://www.virtualaltair.com/virtualaltair.com/images/88-ACR%20Top-150.jpg


                        W Tom S.
                      • corey986
                        Thanks. But I m looking for the older card. My card has a cable attached. It s just got plugs not sockets. I m guessing based upon the pics of the
                        Message 11 of 16 , Dec 21, 2013
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                          Thanks. But I'm looking for the older card. My card has a cable attached. It's just got plugs not sockets. I'm guessing based upon the pics of the advertisement on Virtual Altair that I need to replace the plugs with sockets and by the looks of the sockets they used from the pic I don't have a way to install this right without doing some metal work on the factory screen material, clipping out a big section for the sockets to the holes in the chassis. I was hoping to avoid major work but I guess I'll have to do it at some point.


                          Cheers
                          Corey
                        • wtsnet
                          Corey, I m not sure what you mean by factory screen material. Altair back plates vary in design over the years. Do you have round holes like:
                          Message 12 of 16 , Dec 21, 2013
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                            Corey,

                            I'm not sure what you mean by factory screen material. Altair back plates vary in design over the years. Do you have round holes like:

                            http://www.virtualaltair.com/virtualaltair.com/images/88-ACR%20connector%20%20labels.JPG

                            If not, a small rectangle of phenolic or another material can be used on the retangular hole for a DB-25 connector. This image is for the newer 88-UIO, but a similar approach with two holes would work with the 88-ACR.

                            http://www.virtualaltair.com/virtualaltair.com/images/88-UIO%20cable%20-150.jpg

                            > But I'm looking for the older card. My card has a cable attached. It's just got plugs not sockets


                            The 88-ACR is the older MITS card. Is this the card you have? Is it the 88-SIOB with piggyback MITS Modem card? Do you have a picture? The cable sounds custom with plugs for the cassetter player instead of sockets on the backpanel.


                            W. Tom S.





                            ---In altaircomputerclub@{{emailDomain}}, <no_reply@yahoogroups.com> wrote:

                            Thanks. But I'm looking for the older card. My card has a cable attached. It's just got plugs not sockets. I'm guessing based upon the pics of the advertisement on Virtual Altair that I need to replace the plugs with sockets and by the looks of the sockets they used from the pic I don't have a way to install this right without doing some metal work on the factory screen material, clipping out a big section for the sockets to the holes in the chassis. I was hoping to avoid major work but I guess I'll have to do it at some point.


                            Cheers
                            Corey
                          • corey986
                            The factory had an optional black chicken wire kind of mesh to put over the open port holes. I will have to remove it and cut it. I lost about six months ago
                            Message 13 of 16 , Dec 21, 2013
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                              The factory had an optional black "chicken wire" kind of mesh to put over the open port holes. I will have to remove it and cut it. I lost about six months ago an eBay auction for a spare NOS mesh so I hope I don't mess it up when I clip out space for the jacks. Then I'll have to figure out how to replicate the labels for the ports.

                              Cheers
                              Corey
                            • wtsnet
                              Thanks Cory! Cassettes and mesh are before my time. I started with the 8800b and diskettes. I haven t seen the mesh on an 8800b. Please send a pinture when you
                              Message 14 of 16 , Dec 21, 2013
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                                Thanks Cory!

                                Cassettes and mesh are before my time. I started with the 8800b and diskettes. I haven't seen the mesh on an 8800b. Please send a pinture when you are done.

                                W. Tom S
                              • wtsnet
                                Thanks for the image of the optional MITS screen installed on your mainframe.: http://www.virtualaltair.com/virtualaltair.com/images/MITS%20Screen.jpg
                                Message 15 of 16 , Dec 21, 2013
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                                  Thanks for the image of the optional MITS screen installed on your mainframe.:


                                  http://www.virtualaltair.com/virtualaltair.com/images/MITS%20Screen.jpg


                                  The screen does look nice. Cutting a hole with a nibbler will leave a jagged edge. A rectangular plate like 88-UIO assembly could hide the ragged edge on the inside. The back panel would hide the edge on the outside.


                                • wtsnet
                                  Now that I know what I m looking for, I found a MITS image that shows two screens: http://www.virtualaltair.com/virtualaltair.com/images/Altair_Kits.jpg
                                  Message 16 of 16 , Dec 22, 2013
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                                    Now that I know what I'm looking for, I found a MITS image that shows two screens:

                                    http://www.virtualaltair.com/virtualaltair.com/images/Altair_Kits.jpg



                                    W. Tom S

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