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Thread: Strange video issue with Amiga 1000 and 1084S monitor

  1. #1
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    Default Strange video issue with Amiga 1000 and 1084S monitor

    Folks! Need assistance with a very strange video problem. I recently acquired an A1000 with a 1084S monitor, but it did not come with a video cable. Looking through my parts bin, I hacked up a DB25 and a Roland keyboard connector and did my own RGB cable. Here is where things get interesting:


    The A1000 displays video fine on the 1084S, but ONLY on the Kickstart screen on a cold boot. As soon as I load the Kickstart disc, I get a black screen instead of the usual Workbench floppy screen. At this point I thought my Kickstart floppy was to blame. In an attempt to isolate the problem, I connected a 15khz-compatible LCD monitor and lo and behold, the A1000 displayed the workbench prompt. Plug back the 1084S, and the black screen comes back again.
    Now here is the kicker - if I hook up the 1084S to my A500, it works fine no matter what program I load, which makes me wonder if the video pinout on the A1000 and A500 have slight differences. The easy solution would be to leave the 1084S on the A500 and the LCD on the A1000, but I insist on keeping the 1084S on the A1000.


    This is what I based myself on to build my cable:






    Any clues?

  2. #2
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    I'm wondering if there might be a difference in sync signals, however I have used a 1084s with DIN connector on my A1K...
    Other than that, Is there any chance your cable has a dodgy connection in it, and when it warms up its becoming a weak connection?
    The cable I have is wired like that, however the ground (surround) on the connector are also connected. Have you connected these too?
    Last edited by chiark; 18th June 2020 at 16:23.
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    Hmm, no I don't believe that the ground is connected. Where would that go on the RGB connector?

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    Metal shield of the plug on one end to metal shield of the socket on the other end. There's continuity on those parts on my Commodore cable that came with the monitor.
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    The pins on the Amiga side have separate grounds for red, green, blue, and sync. (pins 16 through 20). Maybe the 500 is more resilient to having the others floating (or connects the grounds together internally or something).

    I'd try connecting those grounds together.

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    Chatted with a.mi.goun. He will build me a buffered video cable in hopes that this will solve my issue.

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    I've never heard of a buffered cable for an RGB monitor... The cable you have built is almost identical to mine, with only the red grounded, but mine has the shields on both sides connected. Doing that at least eliminates one more thing.

    My 1000 is a european one with the daughterboard so is an early machine; I'd expect them to be the most picky.
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    I got my buffered sync RGB cable from a.mi.goun and it works!

    Apparently "big box" amigas (1000, 2000, 3000, 4000) need buffered sync cables.

    Anyway... My non buffered cable works on my A500, so it's win-win.



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    Good to hear! I've never had a problem with unbuffered cable, and I have 2x 1000, 2000, 3000 and 4000 here.
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