OMG actual on-topic ZX81 post from me! - Sinclair

This is a discussion on OMG actual on-topic ZX81 post from me! - Sinclair ; Hello boys! I set my ZX81 up t'other day, and to my horror it doesn't completely work. I get a picture on my TV, but the K is dull white on bright white, not on black. I've tried fiddling with ...

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Thread: OMG actual on-topic ZX81 post from me!

  1. OMG actual on-topic ZX81 post from me!

    Hello boys!

    I set my ZX81 up t'other day, and to my horror it doesn't completely work. I
    get a picture on my TV, but the K is dull white on bright white, not on black.
    I've tried fiddling with the pot, but all this does it change the frequency I
    need to tune my TV into.

    If I retune the TV, I can get a black-backed K, but so much horizontal
    distortion it's impossible to use.

    I've tried two TVs, so I don't think it's that. Even fine-tuning doesn't help.
    So I'm hoping YOU might.

    deKay
    --
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  2. Re: OMG actual on-topic ZX81 post from me!

    deKay wrote:
    > Hello boys!
    >
    > I set my ZX81 up t'other day, and to my horror it doesn't completely work. I
    > get a picture on my TV, but the K is dull white on bright white, not on black.
    > I've tried fiddling with the pot, but all this does it change the frequency I
    > need to tune my TV into.
    >
    > If I retune the TV, I can get a black-backed K, but so much horizontal
    > distortion it's impossible to use.


    Is the TV a new one?
    Because the way the ZX81 produced its picture doesn't agree with modern TVs.
    You need an old black and white (or colour) set from the 80s or before.
    Certainly before they started getting clever with auto compensation and
    white level/black level stuff in chips.

    If you've still got an old black and white portable stashed away somewhere
    (up in the loft, down in the cellar...)
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  3. Re: OMG actual on-topic ZX81 post from me!

    Soni tempori elseu romani yeof helsforo nisson ol sefini ill des Wed, 23 Jul
    2008 10:15:11 +0100, sefini jorgo geanyet des mani yeof do comp.sys.sinclair,
    yawatina tan reek esk Andrew Halliwell fornis do
    marikano es bono tan el:

    >Is the TV a new one?


    Yes.

    >Because the way the ZX81 produced its picture doesn't agree with modern TVs.
    >You need an old black and white (or colour) set from the 80s or before.
    >Certainly before they started getting clever with auto compensation and
    >white level/black level stuff in chips.


    Yes, I thought this was the case, but I've turned everything like that off.
    The second TV I tried is also a recent one, but much less advanced and it's
    exactly the same there.

    >If you've still got an old black and white portable stashed away somewhere
    >(up in the loft, down in the cellar...)


    Sadly no.

    Of interest, is the fact that on my TV, my BBC Micro has a similar problem,
    but the BBC works fine on the other TV. My Spectrum 48 and my 128+ both work
    fine on my TV, as does my Atari 400 and my Videopac.

    deKay
    --
    Lofi Gaming - http://lofi-gaming.org.uk
    Gaming Diary - http://lofi-gaming.org.uk/diary
    Blog - http://lofi-gaming.org.uk/blog
    My computer runs at 3.5MHz and I'm proud of that

  4. Re: OMG actual on-topic ZX81 post from me!

    You can get a small B&W CRT portable tele for about £30 these days
    from various gadget places. That should do the job.

  5. Re: OMG actual on-topic ZX81 post from me!

    OwenBot wrote:
    > You can get a small B&W CRT portable tele for about £30 these days
    > from various gadget places. That should do the job.


    Might still have the same blacklevel problem though, mightn't it?
    It's to do with how the video signal was decoded after all...
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  6. Re: OMG actual on-topic ZX81 post from me!


    "Andrew Halliwell" a écrit dans le message de
    news:3enjl5-nro.ln1@ponder.sky.com...
    | OwenBot wrote:
    | > You can get a small B&W CRT portable tele for about £30 these days
    | > from various gadget places. That should do the job.
    |
    | Might still have the same blacklevel problem though, mightn't it?
    | It's to do with how the video signal was decoded after all...
    Yes,
    But keep in mind, there's severals channels mirror produced by the HF
    modulator.
    Try to looking for another channel around your crapy screen!
    You aloso can retrieve your Tv signal among the modulator box.
    You need to wire a new output to get a direct numeric signal.
    But, if you had to use this hard twick, you had to boost bightness ...



  7. Re: OMG actual on-topic ZX81 post from me!

    Andrew Halliwell wrote:
    > OwenBot wrote:
    >> You can get a small B&W CRT portable tele for about £30 these days
    >> from various gadget places. That should do the job.

    >
    > Might still have the same blacklevel problem though, mightn't it?
    > It's to do with how the video signal was decoded after all...


    I wonder, would it help to take the video signal out as video, rather
    than modulated onto UHF, this is very easy to do in the spectrum... I
    don't know anything about the modulator in the zx81, but I'd wager it's
    similar

    perhaps it's the actual video signal that's not properly formed, in
    which case that would just give you a nice crisp clean, crappy picture

  8. Re: OMG actual on-topic ZX81 post from me!

    hi!

    you can find a simple video out here:

    http://www.zx81.de/english/video_e.htm

    greetings
    jens (german ZX-TEAM)

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