Announcement

Collapse

Forum Rules and 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.


Rule 1: 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.


Rule 2: 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.



Rule 3: 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.


Rule 4: "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.

Rule 5: 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

    There is a note in the build manual somewhere to link pins 19 and 20 on the RS232 connector.

    Jim

    Comment


      Originally posted by Jim Hearne View Post
      There is a note in the build manual somewhere to link pins 19 and 20 on the RS232 connector.

      Jim
      Thanks Jim, I had a good look and found it. I've reworked my RS-232 cable such that the DSR signal is now passed through, and the original DSR detection bit of code now works.

      Stuart.

      Comment


        Newsletter Index

        I've put together an index of the articles and comments in the Cortex newsletters. Copy attached if you want it.

        Stuart.
        Attached Files

        Comment


          if anyone is interested, I may have a line on two more sets of Cortex boards (bare circuit cards only, no other components). No clue on price as of yet, but I figured I'd throw it out here.
          Enter My Mind At Your Own Risk!

          Comment


            I would be interested, I have the 9995 so far.

            Comment


              Originally posted by Ksarul View Post
              if anyone is interested, I may have a line on two more sets of Cortex boards (bare circuit cards only, no other components). No clue on price as of yet, but I figured I'd throw it out here.
              So where have you discovered those, Jim?

              Comment


                Same source as all of the other NOS boards that came out of the woodwork recently, Stuart. He just turned up another pair of board sets. I let him know there was interest in them--now we'll see how much he wants for them. I think he had half as many kits in his loft as there are known survivors from all other sources combined!
                Enter My Mind At Your Own Risk!

                Comment


                  Originally posted by Ksarul View Post
                  Same source as all of the other NOS boards that came out of the woodwork recently, Stuart. He just turned up another pair of board sets. I let him know there was interest in them--now we'll see how much he wants for them. I think he had half as many kits in his loft as there are known survivors from all other sources combined!
                  Did he have more parts kits then ?, i thought he only had the one case and partial kit that i bought with the first board set he put on Ebay.
                  I knew he had more PCB sets, but he said no more parts. (If he does he still owes me a few bits he said he'd send if he found them).

                  I got the impression they were something to do with the company he worked at but he never gave away much detail of where they came from.

                  Jim

                  Comment


                    Originally posted by Stuart View Post
                    I've put together an index of the articles and comments in the Cortex newsletters. Copy attached if you want it.

                    Stuart.
                    Many thanks for doing that, it was something I was going to do at some point but you beat me to it.

                    It's a shame we can't find the missing issues, a couple of people have appeared on here in the past saying they have them but nothing has materialised.

                    I did send you a PM about the caps, do you still need them ?

                    Jim

                    Comment


                      Originally posted by Jim Hearne View Post
                      Many thanks for doing that, it was something I was going to do at some point but you beat me to it.

                      It's a shame we can't find the missing issues, a couple of people have appeared on here in the past saying they have them but nothing has materialised.

                      I did send you a PM about the caps, do you still need them ?

                      Jim
                      Ah, thanks Jim. I thought PMs got e-mailed through and didn't realise your reply was sitting there waiting for me. One each of the two you have would be appreciated if you can spare them. The third I can get from Farnell - looks like they've got a DIN plug that is an exact fit as well. I'll get the E-bus connector and a few other bits as well to make up to the minimum order value.

                      Did your LS2001 replacement PCB ever come to fruition?

                      Stuart.

                      Comment


                        He only had the bare boards, Jim--no other parts (with the exception of the keyboard encoder chip). He's asking 100 pounds for the two board sets, shipped to the US (probably less for addresses in the UK). Nice to see your system getting close to complete, Stuart. It is unfortunate that the folks who noted they had the missing newsletters disappeared before they scanned them for posterity too. . .I'm just glad the we as a group have been able to recover as much as we have!
                        Enter My Mind At Your Own Risk!

                        Comment


                          Just got the set of 4816 RAM chips for the video (one of which is faulty and will need replacing) and got the video working. Interestingly, I've had to add two 33pF caps to ground in parallel with the VDP crystal to get it to oscillate properly, as per the 9918 data manual. But there is no provision for the caps on the board. I wonder if Cortex kits had some type of crystal that didn't need them?

                          Comment


                            I've dozens of tubes of memory chips, i will see if i've any compatible ones. I've certainly got chips for the main memory.
                            I didn't have to put caps on mine, what were the symptoms without them ?
                            Whats your video quality like ?, mine is very poor, it looses colour and frame sync with certain colour combinations and is generally very unstable on the line sync. It's the same on a Wintv card and one TV, and a little better on another TV (Both LCD).
                            I've looked at the video signal for the modulator and it's correct according to the data sheet. The sync is pulling to ground so it's not the problem mentioned in the newsletters.
                            I also replaced the modulator and tried it without the LM1889 so it was just a monochrome signal but had the same problems just in grayscale.
                            I did also try putting heavy duty direct power feeds to the the VDP but that made no visible difference.

                            Caps are in the post today.

                            Jim

                            Comment


                              No caps on the VDP crystal - just no video signal. Looking at the VDP oscillator inputs with a 'scope and the signal is all over the place. Did wonder if it's because I'm using one of the modern "1/4 height" crystals, but the crystal in the VDP data sheet would have been "full height" and the data sheet specifies the caps.

                              I'm using a TMS9918 VDP to give a direct NTSC composite output (with a 560 Ohm resistor to ground). The picture is not great (in terms of clarity, but rock steady as far as sync is concerned), but is consistent with another project where I've used the 9918. See the screenshot at <www.avjd51.dsl.pipex.com/cortex_screen.gif>. The vertical banding looks about the same as the horizontal resolution. I've tried adding a simple transistor buffer stage to the output but it made no difference. Some sort of filtering to smooth the blue background would also smooth the pixels you're trying to see?

                              Now lets compare that with the TI-99/4A which gives a far better picture. There's a circuit diagram of the TI-99 here, with the video circuit on page 60 of the PDF: <www.avjd51.dsl.pipex.com/ti/console_circuit_diagram.pdf>. I've tried the filter circuit on the video output on one of my other systems and that didn't make any difference either. The VDP crystal circuit is not the simple crystal and cap circuit in the data sheet - why the effort for this particular circuit?

                              Does anyone have any 'analogue contacts' who might be able to shed some light?

                              Stuart.
                              Last edited by Stuart; January 31, 2013, 03:25 AM.

                              Comment


                                Jim, thanks for caps. Received and fitted.

                                When you were building yours you said you had a problem with the speaker giving random beeps, and you cured this by replacing the 74LS259. Guess what - I've got exactly the same problem, random beeps a fraction of a second long. I've replaced the 74LS259 with another new one by a different manufacturer and it's made no difference. Has your been totally cured? If I use the MONitor to disable interrupts and put the processor into a loop doing nothing, then the speaker is completely silent, which suggests to me it's a software thing rather than hardware. But then if I (again in the Monitor) change the instructions that switch the 'bell' on to NOPs, I still get the random beeps.

                                Comment

                                Working...
                                X