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UK TRS-80 Model 1 with 260-9800 hi-res graphics addon - debugging

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    UK TRS-80 Model 1 with 260-9800 hi-res graphics addon - debugging

    I've acquired a TRS-80 Model 1, with a UK only Tandy supplied 260-9800 hi-res graphics addon. This is an official add-on from Tandy with an external box containing the increased video ram, and a custom character generator on a daughterboard. A number of wires come from the daughter board to the video section etc.

    The machine was DOA. So, been working through the issues list.

    1. Z80 been replaced with a new part, the reference manual CPU flowchart highlighted the problem, and the scope showed the chip dead.

    2. Horizontal sync was dead, picture rotating horizontally. Z6 replaced, problem fixed. Picture is now rock solid. Interestingly, a decoupling capacitor was between pin 4 and vcc. As i socket'ed the new 74HC04 the capacitor was moved to the rear of the board.

    Next problem.

    On power on the Machine starts with garbage on the screen, and then slowly from bottom right to top left the screen fills with '5C' characters until the whole screen is full. Any ideas?

    #2
    Hi Tarkie,

    That problem with the screen filling with one pair of characters from the bottom right all the way up I have seen before a few times, and it has sometimes been due to a failed ram chip.

    Firstly, remove the 8 ram chips and see if the 5C business stops. It should just be a static screen of random garbage characters.

    Next, install a known good set of Ram chips in and see if that helps. You could also put the set of rams you removed into a known good system and see if that system still functions properly. Then you need to eliminate any bad ram chips... and it might be more than one.

    Hope this helps,

    Ian.
    *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

    Comment


      #3
      Thanks Ian, will report back.

      Comment


        #4
        Originally posted by TRS-Ian View Post
        Hi Tarkie,

        Firstly, remove the 8 ram chips and see if the 5C business stops. It should just be a static screen of random garbage characters.
        After removal of RAM, system boots with garbage, no 5C, but then the screen changes to a screen full of @S instantly.

        Steve

        Comment


          #5
          Updates:

          * installed a new keyboard cable. The other finally gave up the ghost.
          * Pulled the RAM and now the screen boots with Garbage, and then fills immediately with "@S" and has the slight flicker

          Comment


            #6
            Originally posted by Tarkie101 View Post
            Updates:

            * installed a new keyboard cable. The other finally gave up the ghost.
            * Pulled the RAM and now the screen boots with Garbage, and then fills immediately with "@S" and has the slight flicker
            Just an update.

            System had a dead 4116. Now fully functional.

            38235129_10156420553059333_4381577192719515648_n.jpg

            Comment


              #7
              Hey Steve can I have DMKs of those disks which came with the HRG ?
              *There is never a charge for Tech Support even if you don't purchase from me - We are Enthusiasts Helping Other Enthusiast and that is just the way it is

              Comment


                #8
                Does anyone have more information on this hardware? It’s a fascinating piece of kit that I have not seen before.
                Pete
                http://pski.net

                Comment


                  #9
                  Viva le (hi) resolution!

                  I'm also glad to see a living instance of this rare creature.

                  The user manual and software for the TRS-80 Model I High Resolution Graphics hardware product (Cat. No 260-9800, available only in the UK) have been available on the web for more than a decade, but the manual scan is missing the cover page and catalog number, and it got miscategorized on Ira Goldklang's trs-80.com as a software manual, and as a result it seems little-known that this was a real official hardware product sold by Tandy.

                  See "TRS-80 Manual: High Resolution Graphics (19xx)(Microware-Microfirm)", High Resolution Graphics Demonstration Disk (19xx)(Author Unknown)[DMK].zip, and High Resolution Graphics Setxy and Print (19xx)(Author Unknown)[DMK].zip

                  Also contributing to the hardware's obscurity is the lack of any online archives of the UK's Tandy TRS-80 Microcomputer NEWS. There's someone with a few issues of it for sale on Ebay, and the listings include a picture of the front cover of the April 1982 issue, with a very exciting cover story about the high-res mod. I've typed in the whole thing below, and it's made me bloodthirsty for pixels. Who knew the King was hiding them in the Bastille?

                  Tandy TRS-80 Microcomputer NEWS April 1982 cover Up The Resolution.jpg

                  UP THE RESOLUTION!

                  Like all revolutions the people -- Model I owners in this case -- had to win in the end. We've taken notice of the unrest on the streets and once again stormed the bastile [sic] of computer technology, liberating you to "HIGH RESOLUTION GRAPHICS" (if there's a head you've been calling for, this is it!) ........ It's been a long time coming but HERE IT IS (you can stop 'phoning at all hours of the day and night now!)

                  In theory it's been easy; we've always known what you want but practicality has always been the big restriction. You want High Res -- but you don't want a sadly depleted memory (there's the rub) or a huge bill. There's the question of suitable design and the software to utilize the new features (not so easy is it?)

                  Now you'll be pleased to hear these fences have been jumped and the '4-faults' have been overcome:-

                  MEMORY -- The Memory capacity of your keyboard will hardly be used. The High Res Mod has all its own RAM and ROM on board! Now that the character generator is software controlled we can design up to 128 characters as well as the standard ASCII set (including lower case). This increases the resolution by twelve times to 384 x 192.

                  DESIGN -- Finding a suitable design was not at all easy. The upgrade consists of a small metal box, external to the Level II keyboard, connected to the expansion port (or expansion interface) and also via a new connector that needs installing inside the keyboard.

                  One of the most important criteria for a modification like this is that it must be invisible to the system when not required; with the High Res Mod an OUT Statement from BASIC will switch it in or out.

                  SOFTWARE -- Without software, of course, its like it's like [sic] having a car without a steering wheel. The software supplied provides the facility to design your own characters and save them on disk or tape. These characters can be used from BASIC in exactly the same way as existing graphics characters are called.

                  MONEY -- For 179 the modification includes the installation of the hardware, a comprehensive manual and the necessary software, with demonstration programs. (It's all British Too!)

                  We've been fascinated by the new capabilities that High Resolution Graphics can offer for design, animation and games -- but don't take my word for it, call in and try one for yourself.

                  VIVA LE (HI) RESOLUTION!
                  -Alan

                  Comment


                    #10
                    I have one of these attached to my Model I system. Yes, I'm in the UK. There was a wire link fix that was sent out; does yours have it? I can't remember what it was for though.

                    Can the system operate without the box connected as it uses the expansion port and some of the recent modern add-ons don't have an expansion connector fitted and I would like to try them? What I could do with is an expansion port doubler.

                    Comment


                      #11
                      Apologies, life got in the way.

                      @IAN, i was hoping to DMK the disk this weekend, but life got in the way. Once i've done so, i'll of course share so it is preserved.

                      Comment


                        #12
                        The disk referenced here is the image of the disk I have.

                        Comment


                          #13
                          Originally posted by multivac View Post
                          I have one of these attached to my Model I system. Yes, I'm in the UK. There was a wire link fix that was sent out; does yours have it? I can't remember what it was for though.

                          Can the system operate without the box connected as it uses the expansion port and some of the recent modern add-ons don't have an expansion connector fitted and I would like to try them? What I could do with is an expansion port doubler.
                          No idea about the "Wire link fix" - what do i look for to confirm?

                          Comment


                            #14
                            Originally posted by Tarkie101 View Post
                            No idea about the "Wire link fix" - what do i look for to confirm?
                            You will have to open the case though and you might see an additional wire fix. My case does not have the Tandy label on the outside so I might have had the add-on fitted to my keyboard by the original manufacturer and not Tandy. Does anyone have a picture of the inside?

                            Comment


                              #15
                              Took some closeup photo's of the inside of the add-on memory board in the external box. Also included the back of the main motherboard which has a single orange wire added to the back.

                              https://photos.google.com/share/AF1Q...p5cm5CeUp6MGln

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