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Help testing a C128D video issue

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  • azog.thoth
    Hi all, Part time lurker here, so forgive me for jumping in, but this is the first place I figured to look for assistance. I m trying to trouble-shoot an issue
    Message 1 of 5 , Jul 7, 2011
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      Hi all,

      Part time lurker here, so forgive me for jumping in, but this is the first place I figured to look for assistance.

      I'm trying to trouble-shoot an issue on a Commodore 128D which won't display 80 column video. I've tried both monochrome video thru the 9-pin video part, as well as a scan-doubler to convert CGA to VGA, but I get the same basic results, a simple black screen. 40 column mode works fine.

      The 128D uses a different VDC than the regular 128, so getting a scrapped 128 isn't a real solution.

      Anyways, the VDC is an 8568, identified as U22, a socketed device under the shielded box directly below the power supply, so access is easy. If someone has a working C128D in 80 column mode (either monochrome or RGB), and is willing to pop it open, I'd like send you my VDC so you can try it and verify either dead or alive.

      You can contact me off-list. Thanks!
    • B Degnan
      What monitor model are you using. The 1802? Does the monitor you re using work in 80 col mode with a regular C128? I have a spare 8568 if you want to buy it
      Message 2 of 5 , Jul 8, 2011
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        What monitor model are you using. The 1802? Does the monitor you're
        using work in 80 col mode with a regular C128? I have a spare 8568
        if you want to buy it from me, make offer.
        Bill

        At 05:58 PM 7/7/2011, you wrote:
        >Hi all,
        >
        >Part time lurker here, so forgive me for jumping in, but this is the
        >first place I figured to look for assistance.
        >
        >I'm trying to trouble-shoot an issue on a Commodore 128D which won't
        >display 80 column video. I've tried both monochrome video thru the
        >9-pin video part, as well as a scan-doubler to convert CGA to VGA,
        >but I get the same basic results, a simple black screen. 40 column
        >mode works fine.
        >
        >The 128D uses a different VDC than the regular 128, so getting a
        >scrapped 128 isn't a real solution.
        >
        >Anyways, the VDC is an 8568, identified as U22, a socketed device
        >under the shielded box directly below the power supply, so access is
        >easy. If someone has a working C128D in 80 column mode (either
        >monochrome or RGB), and is willing to pop it open, I'd like send you
        >my VDC so you can try it and verify either dead or alive.
        >
        >You can contact me off-list. Thanks!
        >
        >
        >
        >
        >------------------------------------
        >
        >Yahoo! Groups Links
        >
        >
        >
      • Evan Koblentz
        ... Such topics are best when discussed on-list, not off-list. When on-list, the answers become part of our public archive and therefore they help everybody.
        Message 3 of 5 , Jul 8, 2011
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          >>> You can contact me off-list

          Such topics are best when discussed on-list, not off-list.

          When on-list, the answers become part of our public archive and therefore they help everybody.

          When off-list, the answers get lost, few people gain from it, and (quite frankly) it implies that a lurker doesn't care much about our group other than "help me" .....
        • azog.thoth
          Well, this is all part and parcel of the issue. I picked this C128D up about three years ago, and do not have a Commodore monitor. Based on this forum
          Message 4 of 5 , Jul 8, 2011
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            Well, this is all part and parcel of the issue. I picked this C128D up about three years ago, and do not have a Commodore monitor. Based on this forum (http://www.commodore128.org/index.php?topic=453.msg3349#msg3349), I acquired the same converter to connect it to a VGA monitor.

            However, I feel the issue goes beyond the convert to the C128D video itself, because before even acquiring this video adapter, I attempted to use 80 column monochrome on a composite video display, which also did not work. Pin 7 of the 9-pin video port provides monochrome 80 column mode, so all you need to do is connect it (and gnd) to an RCA jack. I did this years ago on my original C128D, and this forum reaffirms my memory (http://www.commodore128.org/index.php?topic=1725.0)


            --- In midatlanticretro@yahoogroups.com, B Degnan <billdeg@...> wrote:
            >
            > What monitor model are you using. The 1802? Does the monitor you're
            > using work in 80 col mode with a regular C128? I have a spare 8568
            > if you want to buy it from me, make offer.
          • B Degnan
            ... That s very possibly your problem. ... I would suggest regardless you get a Commodore 1950 or 1802 and try those, with the proper cable (four wire).
            Message 5 of 5 , Jul 8, 2011
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              At 09:11 AM 7/8/2011, you wrote:
              >Well, this is all part and parcel of the issue. I picked this C128D
              >up about three years ago, and do not have a Commodore monitor. Based
              >on this forum
              >(http://www.commodore128.org/index.php?topic=453.msg3349#msg3349), I
              >acquired the same converter to connect it to a VGA monitor.

              That's very possibly your problem.

              >However, I feel the issue goes beyond the convert to the C128D video
              >itself, because before even acquiring this video adapter, I
              >attempted to use 80 column monochrome on a composite video display,
              >which also did not work. Pin 7 of the 9-pin video port provides
              >monochrome 80 column mode, so all you need to do is connect it (and
              >gnd) to an RCA jack. I did this years ago on my original C128D, and
              >this forum reaffirms my memory
              >(http://www.commodore128.org/index.php?topic=1725.0)
              >

              I would suggest regardless you get a Commodore 1950 or 1802 and try
              those, with the proper cable (four wire). It's very possible that
              I am wrong, but I would rule out the possibility that you have the
              wrong monitor/cable combination first. I know that with the Amiga
              systems this is also an issue.

              Bil Herd, if he's monitoring this thread would be the authority on the subject.

              Bill
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