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This forum is part of our mission to promote the preservation of vintage computers through education and outreach. (In real life we also run events and have a museum.) We encourage you to join us, participate, share your knowledge, and enjoy.

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Powertran Cortex

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    Some issues with the new Cortex, apart from lack of lunchtimes to work on it.

    First problem was no keyboard input, this turned out to be the keyboard encoder chip, it just wasn't oscillating, a new chip fixed that.
    Second problem, the display is a very washed out dark grey text on a white background, i suspect it's not right, what colours should it be ?
    Third problem, i can only enter text for a few seconds and then it either locks up or starts flashing random junk on the screen, reseting the board does nothing, i just get a blank screen.
    I have to let it "rest" for 10 mins and then it will work again for a few seconds, obviously something is not happy.
    I'm going to make up the status LEDS next so i can see what they do, then get busy with the scope/logic analyser.

    Thanks,

    Jim

    Comment


      Update.

      With the new keyboard decoder the display resonded to keypresses but they were graphics characters as if you had graphics key pressed.
      This turned out to be a duff 74LS251 chip, IC63 i swapped it with IC62 (same chip but used to read floppy jumpers etc) and the keyboard worked correctly.

      The locking up after a few seconds seems to be the processor itself, if i keep it cold with freezer spray it will stay working.
      I kept if frozen long enough to type in the colour bar test program and this confirmed that there is no colour output, so something else to find.

      Anybody got a TMS9995 processor for sale at a sensible price ?

      Given that all these chips were new and have been unused for almost 30 years i'm quite suprised how many have failed.

      Thanks,

      Jim

      Comment


        Originally posted by Jim Hearne View Post

        Given that all these chips were new and have been unused for almost 30 years i'm quite suprised how many have failed.

        Thanks,

        Jim
        Electronics tend to deterioriate extremely rapidly when not used. Especially capacitors.
        So if you get anything that hasn't been used for 30 years, all sorts of problems can arise.

        Comment


          I'm used to it with caps, hence i fitted all new caps and resistors.
          Chips i've not come across it as being such a problem before, maybe because these were never used until now, and it's different from 30 year old chips that are fitted in equipment and were used early in there life.

          Thanks to somebody on this list i think i've a TMS9995NL-12 on it's way to me.

          Jim

          Comment


            I've been pretty harried this week (the mother-in-law arrived for an extended visit yesterday), but I should be able to pop one into the mail on Monday, Jim.
            Enter My Mind At Your Own Risk!

            Comment


              Originally posted by Jim Hearne View Post
              Hi All,
              Would anybody be interested in a plug in 74LS2001 replacement.
              I've done a PCB (14mm x 28mm) for one based on the 1985 ETI article but using surface mount 74LS04 and 74LS74 IC's.
              But the cheapest i can get the PCB made is 96 for any quanity up to 40 off.
              Anybody interested in a assembled module for say 15 +P&P (or less if if more than 10 people are interested but i doubt that !) to help spread the cost.

              Thanks,

              Jim
              I'm new to the forum and am attempting to build 2 Cortex(s) from scratch. As you can imagine, I'm struggling to locate 2 SN74LS2001(s). Count me in.

              Comment


                Originally posted by coryklatt View Post
                I'm new to the forum and am attempting to build 2 Cortex(s) from scratch. As you can imagine, I'm struggling to locate 2 SN74LS2001(s). Count me in.
                Hi,
                I'm still hoping to do the 74LS2001 pcb but by fitting it on some spare space on a PCB here for work.
                Typically the boards i added it to aren't being ordered just yet but should be early next year.

                I have found various errors and ommisions in the documention available, i'll upload my updated parts list later.
                The Cortex 2 build manual is the most correct i've found if you are using the PCB's that were on Ebay recently.

                Good luck,

                Jim

                Comment


                  What's the news Jim? Have you managed to get it running properly yet?

                  Comment


                    Any progress on the build, Jim? Did the chips I sent you work out?
                    Enter My Mind At Your Own Risk!

                    Comment


                      Unfortunatly, due the death of my girlfriends ex-husband we now have her son in the house and a lot of the contents of his house as well.
                      That in conjunction with moving into a smaller unit at work has meant i've had nowhere to setup the Cortex and the test gear.
                      However, next week there are 2 off 17' x 10' buildings being assembled in the garden, one for my metalwork workshop, and the other for a hobby room which my share of will be for my electronics stuff.
                      So, once i've insulated and lined them i should have plently of space to work on the Cortex.

                      Updates will be here as soon as i have something to update.

                      Jim

                      Comment


                        How about the people here who bought the other NOS pcb's, how are you getting on ?

                        Jim

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                          Just waiting for you to iron the bugs out of the assembly instructions Jim. Good to hear you're getting some space to carry on playing.

                          Stuart.

                          Comment


                            TMX9909s on ebay - item 120901292390.

                            Stuart.

                            Comment


                              Thanks Stuart,
                              I just bought one as a spare incase it's differnet to the ones that other Jim kindly sent me for testing.
                              Sheds are built, i just need it to stop raining so i can fully waterproof, insulate and line them !!

                              Jim

                              Comment


                                Hi all,

                                I've just rescued my Cortex (Mk 1) from my mum's loft and now need to reassemble it and see if it still works.

                                Steve

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