Old TV as a ZX80 monitor may not be optimum

Discussions about Sinclair ZX80 and ZX81 Hardware
Creator
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Joined: Wed Jul 27, 2022 3:11 am

Old TV as a ZX80 monitor may not be optimum

Post by Creator »

New to the forum good to see interest in the likes of ZX80 lives on. Not long ago I came across an old box that had my ZX80 from back in the day. Also in the box was a 16K dynamic memory card. It was a project I did for a guy who thought he could sell it. Only this prototype exists, the guy died decades ago The memory bank itself was hacked from a product the company I worked for at the time. I generated interface hardware to make it work with the ZX80. I wondered if it would still work. Also in the box was a hand written block of test code for it, about 15 lines. I typed in the code and it ran several passes without error. Great, but no way to save the code. Later I was thinking about what a disaster the cassette storage device was/is and had thoughts about a better way. Well, I just finished a 'proof of concept' project on using a SDcard as a ZX80 storage device. It works fine, is consistent and reliable but along the way I struggled with what a complete disaster trying to use an old TV as a monitor is. It failed once, I had to order a Sam's manual, troubleshoot and ended up replacing an open resistor in the vertical circuit to get it going again. Anyway, is there a better way ? Pointers to circuits, projects, commercial products etc would be appreciated.
Moggy
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

Hi there Creator and welcome aboard.

There is as you say a small interest in the old 80 and some of us are not afraid to butcher the old girl to make it more workable in the modern era.

Speaking just for myself I use one of these board for a composite video output and damn fine they are too..

https://www.ginger-electronic.com/en/re ... -zx81.html

To keep it cool swap out the old regulator for one of these...

https://uk.farnell.com/tracopower/tsr-1 ... price=true

Available from other suppliers also.


For the load and save jobby most of use the ZXpand module which includes 16k RAM (for the 80, 32k for the 81) with built in SD card save/load but this requires a custom ROM and seeing as you have your own SD card solution not something to bother with I would have thought but mentioned anyway.


So yes welcome again and have fun!
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

Moggy

Thanks for the info, I was not aware of those power modules. I just tried to order a video modules but can't due to required payment method. Are there other places to order from, I'm in US?
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

Are these compatible with US TV's (NTSC) ?
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1024MAK
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Re: Old TV as a ZX80 monitor may not be optimum

Post by 1024MAK »

The DC/DC converter / switching regulators are available from three different manufacturers, and all the main electronic suppliers should carry at least some. The topic about them is here. That’s now quite an old topic, so some of the links may no longer work. But if you search for electronic suppliers and then put the part numbers into their site search site, it should not take long to find some.

I don’t recommend you buy from China, or buy any of the generic DC/DC boards / modules from trading sites like eBay. Only buy from a respectable known supplier.

The ZX8-CCB video board should work fine with both 625 line/50Hz and NTSC 525 line/60Hz video. You will need to adjust the variable resistors (potentiometers/presets) to set the timing up correctly. It’s only available from the web site that Moggy linked to. If you’re having problems, the designer (PokeMon) is a member on these forums.

Mark
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Lardo Boffin
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Lardo Boffin »

Welcome on board!

The SDcard interface project sounds interesting.
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TS 1000 iss 3, ZXPand AY and +, ZX8-CCB, ZX-KDLX & ChromaSCART
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Moggy
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

1024MAK wrote: Thu Jul 28, 2022 6:02 am The DC/DC converter / switching regulators are available from three different manufacturers, and all the main electronic suppliers should carry at least some. The topic about them is here. That’s now quite an old topic, so some of the links may no longer work. But if you search for electronic suppliers and then put the part numbers into their site search site, it should not take long to find some.

I don’t recommend you buy from China, or buy any of the generic DC/DC boards / modules from trading sites like eBay. Only buy from a respectable known supplier.

The ZX8-CCB video board should work fine with both 625 line/50Hz and NTSC 525 line/60Hz video. You will need to adjust the variable resistors (potentiometers/presets) to set the timing up correctly. It’s only available from the web site that Moggy linked to. If you’re having problems, the designer (PokeMon) is a member on these forums.

Mark
Excellent advice as always Mark.
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

Mark
Thanks for the info, sounds like the video board will work for me. I found a guy on eBay who has a supply. If that doesn't pan out I try Ginger-electronics/PokeMon again.

Laedo Boffin
My SDcard project (Xiao, Op Amp, software) is kinda interesting but has its limits, really just a 'can I make this work' kinda thing. It uses existing Load & Save commands so really no speed increase. On Save it monitors the data stream storing all valid pulses then when complete parses and converts to 1's & 0's which are saved to SDcard file so savable ZX80 program size is limited by available memory (currently 32k Xiao). An improvement would be to monitor / parse on the fly but that presents some issues I haven't tackled yet but may in the future. Load is just reading the SDcard file and generating proper pulse patterns for the stored 1's & 0's.
Moggy
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Moggy »

A note of caution re the ebay video boards especially the ones that have a 555 chip installed. I do believe that some people have had problems with these devices. The boards supplied by Pokemon (Ginger-electronics) are the ones used nearly exclusively by most here and are trouble free in my experience (they also have an option for inverse video) and work perfectly on my ZX80.
I don't have any affiliation to ginger electronics other than Pokemon being a member here and being happy with his product.

Mark is more technically minded re these things and his advice I follow to the letter so perhaps his opinion on said ebay 555 boards would beneficial.
Creator
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Re: Old TV as a ZX80 monitor may not be optimum

Post by Creator »

Looks like the same product. https://www.ebay.com/itm/174949505611
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