New member, would like to use my old zx81 with a computer monitor, how can I do it ?

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peepee
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Joined: Wed Jun 22, 2016 11:42 pm

New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by peepee »

I would like to use my old zx81 with a computer monitor, how can I do it ? any advice would be appreciated. thanks.
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RetroTechie
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Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by RetroTechie »

Welcome to this forum, peepee! :)

The ZX81 outputs an RF signal, which means you need a TV.

Another option is a small modification to the ZX81, which makes it output composite video. An example can be found here: http://www.zx81.de/english/video_e.htm
At which point any TV or monitor with a composite video input will do. That is also: any SCART input equipped TV, and some computer monitors also have a comp.video input.

For example a cheapo VGA monitor won't work. Well, unless you put some screen-grabbing-converter-thingie in between. Which also exist... :?
peepee
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Joined: Wed Jun 22, 2016 11:42 pm

Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by peepee »

Thanks RetroTechie,
I think I will try to find an old 625 line tv, one of the old small portable would do, I haven't got room for the big oldies.
I have several other Spectrum models which I would like to check if they are still in working order, I didn't want to modify my zx81 as I'm a bit of a collector and I like things to be original, I was just hoping there was an add-on gadget I could find or a circuit I could build !!!
Thank you for your information, I have made a copy of it, and will let you know how I get on. peepee.
gozzo
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Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by gozzo »

best is to try and get an old black & white set, as these normally work well with a zx81 or zx80, unlike most colour TVs, as the zx80 and some zx81s dont generate the 'back porch' part of the TV signal. as for driving VGA monitors, i have seen in mentioned somewhere that SOME (LCD types only?) can handle a normal TV-like signal, such as 15.625khz line, 50hz frame, which is of course what a zx81(UK type) outputs, but circuitry would still be required to get a composite out from the zx81 and then sync separator for the monitor (Maplin 'used' to sell one of these 'cables' , at high price, but not now..?)
peepee
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Joined: Wed Jun 22, 2016 11:42 pm

Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by peepee »

Thanks gozzo,
you are right about the old black and white tv's best for the zx81, I relegated mine to the tip years ago, clang, glang. now I've got to find another, but its got to be a small portable. You never know what might come up for sale in the local auctions, or car boot sales.
Thanks for your help. regards, peepee.
gozzo
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Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by gozzo »

I see a fair few of the little 5 inch things at car boot sales round here, even if they are not big enough, may be possible to use the innards as a 'receiver/demodulator', tapping off the video signal to feed into a modern horrid digital based thing!i have come across a sync processor chip used in old analogue Pace satellite receivers , it can generate correct sync pulses even when the video signal its fed with drops out, so that could be used to keep up a signal preventing 'blue screen' on the tv, and fill in the missing back porch!
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-B-
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Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by -B- »

I would go for the composite modification. Then you have an easy connection to most TVs...
Image

Then you could also use something like this to get from composite to VGA...
Image

-B-
peepee
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Joined: Wed Jun 22, 2016 11:42 pm

Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by peepee »

Thanks for the photo's, they say a picture is worth a 1000 words, it does explain a lot.
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1024MAK
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Re: New member, would like to use my old zx81 with a computer monitor, how can I do it ?

Post by 1024MAK »

Welcome on board Peepee!

:D :D :D

Please do have a good look around. There is still plenty going on in the ZX World 8-)

Mark
ZX81 Variations
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ZX81 Video Transistor Buffer Amp

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Step up to red alert. Sir, are you absolutely sure? It does mean changing the bulb :!:
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