Announcement

Collapse

Forum etiquette

Our mission ...

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.

This forum has been around in this format for over 15 years. These rules and guidelines help us maintain a healthy and active community, and we moderate the forum to keep things on track. Please familiarize yourself with these rules and guidelines.


Remain civil and respectful

There are several hundred people who actively participate here. People come from all different backgrounds and will have different ways of seeing things. You will not agree with everything you read here. Back-and-forth discussions are fine but do not cross the line into rude or disrespectful behavior.

Conduct yourself as you would at any other place where people come together in person to discuss their hobby. If you wouldn't say something to somebody in person, then you probably should not be writing it here.

This should be obvious but, just in case: profanity, threats, slurs against any group (sexual, racial, gender, etc.) will not be tolerated.


Stay close to the original topic being discussed
  • If you are starting a new thread choose a reasonable sub-forum to start your thread. (If you choose incorrectly don't worry, we can fix that.)
  • If you are responding to a thread, stay on topic - the original poster was trying to achieve something. You can always start a new thread instead of potentially "hijacking" an existing thread.



Contribute something meaningful

To put things in engineering terms, we value a high signal to noise ratio. Coming here should not be a waste of time.
  • This is not a chat room. If you are taking less than 30 seconds to make a post then you are probably doing something wrong. A post should be on topic, clear, and contribute something meaningful to the discussion. If people read your posts and feel that their time as been wasted, they will stop reading your posts. Worse yet, they will stop visiting and we'll lose their experience and contributions.
  • Do not bump threads.
  • Do not "necro-post" unless you are following up to a specific person on a specific thread. And even then, that person may have moved on. Just start a new thread for your related topic.
  • Use the Private Message system for posts that are targeted at a specific person.


"PM Sent!" messages (or, how to use the Private Message system)

This forum has a private message feature that we want people to use for messages that are not of general interest to other members.

In short, if you are going to reply to a thread and that reply is targeted to a specific individual and not of interest to anybody else (either now or in the future) then send a private message instead.

Here are some obvious examples of when you should not reply to a thread and use the PM system instead:
  • "PM Sent!": Do not tell the rest of us that you sent a PM ... the forum software will tell the other person that they have a PM waiting.
  • "How much is shipping to ....": This is a very specific and directed question that is not of interest to anybody else.


Why do we have this policy? Sending a "PM Sent!" type message basically wastes everybody else's time by making them having to scroll past a post in a thread that looks to be updated, when the update is not meaningful. And the person you are sending the PM to will be notified by the forum software that they have a message waiting for them. Look up at the top near the right edge where it says 'Notifications' ... if you have a PM waiting, it will tell you there.

Copyright and other legal issues

We are here to discuss vintage computing, so discussing software, books, and other intellectual property that is on-topic is fine. We don't want people using these forums to discuss or enable copyright violations or other things that are against the law; whether you agree with the law or not is irrelevant. Do not use our resources for something that is legally or morally questionable.

Our discussions here generally fall under "fair use." Telling people how to pirate a software title is an example of something that is not allowable here.


Reporting problematic posts

If you see spam, a wildly off-topic post, or something abusive or illegal please report the thread by clicking on the "Report Post" icon. (It looks like an exclamation point in a triangle and it is available under every post.) This send a notification to all of the moderators, so somebody will see it and deal with it.

If you are unsure you may consider sending a private message to a moderator instead.


New user moderation

New users are directly moderated so that we can weed spammers out early. This means that for your first 10 posts you will have some delay before they are seen. We understand this can be disruptive to the flow of conversation and we try to keep up with our new user moderation duties to avoid undue inconvenience. Please do not make duplicate posts, extra posts to bump your post count, or ask the moderators to expedite this process; 10 moderated posts will go by quickly.

New users also have a smaller personal message inbox limit and are rate limited when sending PMs to other users.


Other suggestions
  • Use Google, books, or other definitive sources. There is a lot of information out there.
  • Don't make people guess at what you are trying to say; we are not mind readers. Be clear and concise.
  • Spelling and grammar are not rated, but they do make a post easier to read.
See more
See less

Powertran Cortex

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

    Welcome Steve,

    The perceived wisdom seems to be to test the power supply before (re-)connecting it to the main board.

    What was the spec of your Cortex? Disk drives?

    Stuart.

    Comment


      It's the original version with no addons. I cannibalised some parts from it years ago, so I need to replace those before I can test it.

      Steve

      Comment


        Is there any source for Cortex PCBs? I did own one and was made throw it out - something to do with marriage. I would really like to build one again.

        Comment


          A few of them turned up on eBay within the last year or so that were actually new old stock Cortex II boards. Other than finding a deal like that, your only options now would be to find an assembled one for sale (they do turn up now and then) or to take the time to do a new board layout (a bit expensive to do the boards though, as there isn't a huge base of Cortex owners out there). Patience is the real key--I had to hunt for several years before I found one, but they've started to turn up a lot more often since I started this thread a few years ago.
          Enter My Mind At Your Own Risk!

          Comment


            Finally got my recently built Cortex kit back onto the bench in the new workshop.
            Still got one of the 2 old problems, it sees keypresses from the keyboard but not the correct ones.
            Without shift, ctrl etc pressed most keys generate a space on the display.
            With control pressed most keys generate graphics characters.
            The graphics key and shift don't seem to alter what the keys do.
            The signals leaving the keyboard seem correct but i will be sure tonight when i get the USB logic analyser hooked up to it.
            Then it's going to be looking at the input port chips on the motherboard, i've already swapped the chip out but that hasn't helped.
            Though, when i was working on it before swapping the chip input out (74LS251) did cure the problem for a short period of time.

            At the moment the seeming overheating of the cpu problem seems to have gone, but did i swap the CPU out when i was working on it back in last November, i can't remember

            Jim

            Comment


              Confirmed that the keyboard is outputing the correct data, next task is to find out why it's not being read and displayed correctly by the system.

              Quite often during the incorrect keyboard reading (most of which come up as spaces) the system jumps from Basic into a monitor program.
              How is one supposed to access the monitor normally ?

              Thanks,

              Jim

              Comment


                Jim, according to the manual, the monitor is accessed by typing MON at the BASIC prompt.

                Stuart.

                Comment


                  Thanks Stuart, that has confirmed what i thought, the system shouldn't be jumping straight to the Monitor from a keyboard press.
                  Shortly afterwards the system started locking up again, and not restarting with reset or power cycle until powered off for a few mins.
                  I managed to find the spare cpu that other Jim kindly send me ages ago and fitted that, that got rid of the lockups and unexpectedly got rid of most of the keyboard problems.
                  The only problem left with the keyboard is that sometimes the case of the letters was wrong and the number keys did control characters, this turned out to be corroded pins on the keyboard control chip.
                  The original that came with the keyboad was dead, not oscilating. The replacement from Ebay was s/h and had corrosion on the tops of some of the legs, i thought they were ok on the lower section but it seems not. A good scrub with the fibreglass pen and all is working correctly in the keyboard dept.
                  Next bit to look at is the video out, i'm currently feeding the TV out into a Wintv card in a PC and the picture is pretty awful, very unstable with lots of noise on the picture.

                  Jim

                  Comment


                    I'm glad the chip came in useful, Jim! Let me know if there are any others that give you sourcing problems during the build--I might have some. I also found a bunch of newer keyswitches with caps that may work as substitutes for some of the original ones. I bought some but I haven't tried them for fit yet--but they do come with a two-part cap, so they are pretty much usable for any regular keytop position that doesn't need to lock.
                    Enter My Mind At Your Own Risk!

                    Comment


                      Originally posted by BillEaves View Post
                      PS. I should also have all the Cortex User Group newsletters still around somewhere.
                      If you can scan in and upload issues 1, 5, 8 and issue 22 onwards (if they exist) then it would complete the current set that is available.
                      I'm especially interested in issue 8 as i believe it has details on the various 74LS2001 replacement circuits.

                      Many thanks,

                      Jim

                      Comment


                        Many thanks Jim. I'll test out the TMX9909 chips you sent me once i have the system stable without the FDC chips fitted.
                        I'll also do a resistance and diode test comparison between your chips and the TMS9909 i got from China before i try the Chinese one in the board.
                        It's not uncommon for Chinese chips to be something totally different remarked.

                        At the moment the intermittent keyboard reading problem has come back, it worked perfectly for about 2 hours the other day then started displaying spaces instead of characters.
                        Pressure on certain areas of the main board around the input port chips made it read the correct keys while the pressure was applied, so i guess i've got a dodgy IC socket there somewhere. They were all brand new so it's a bit of a pain.

                        I tried it on a normal TV (LCD) instead of the Wintv card in the PC and the picture quality was much better, even more so once i turned off the PC.
                        Probably normal for this age of computer on a TV output but it does have the problem mentioned in the newsletters of being too far to the left.

                        Jim

                        Comment


                          Will be interesting to hear the results of the TMS9909 from China. If you were going to remark a chip, wouldn't you choose to do something a bit more common? I wouldn't have thought that the world-wide market for this particular chip extends very far from just this forum ...?

                          Stuart.

                          Comment


                            Who knows how they decide what to fake.
                            We had several 100 MAX479 quad opamps at work that were actually remarked 7404 type hex invertors, i even connected one up and it worked as one.
                            Also 78L05 and PCF8577 chips that were just empty packages with no silicon inside.
                            These were from mainstream UK suppliers, not direct from China.

                            Jim

                            Comment


                              Blank message. please ignore.

                              Comment


                                Latest update.
                                Another session with the Logic analyser revealed that there were 2 problems with the keyboard input, one was that D0 was always high, the other that D2 was stuck at about 2v with a very poor signal.
                                D0 turned out to be the ribbon cable not crimped quite well enough in the IDC connector, probably why the problem had been intermittent, should have checked the cable ages ago !
                                D2 was a faulty 74LS157 on the keyboard.
                                An unlikly occurance happened when i went to look for a replacement 74LS157, i took down all my tubes of chips and in doing so a 40 pin chip dropped on the floor, i picked it up and looked at the part number, it was only another 2376 keyboard controller.
                                I had no idea i even had one, i bought a replacement for the dead original off ebay but haven't been happy with the rusty pins.
                                So i've fitted the newly found one (which works) and kept the rusty one as a spare.
                                Touch wood, the keyboard problems are finally banished.
                                Now to get on and test the tape and serial ports and then fit the floppy drive interface chips.

                                Jim

                                Comment

                                Working...
                                X