How to mod a US ZX80 to work in New Zealand

Discussions about Sinclair ZX80 and ZX81 Hardware
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nama
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How to mod a US ZX80 to work in New Zealand

Post by nama » Wed Sep 20, 2017 1:25 pm

So I'm In NZ, and I have two ZX80's, both from the US. Neither seem to work here, but both worked when I lived in Japan. One has a composite video mod.
Is the reason they don't work have anything to do with the fact that NZ is 60hz power and the US is 50hz?

Cheers

Phil

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1024MAK
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Re: How to mod a US ZX80 to work in New Zealand

Post by 1024MAK » Wed Sep 20, 2017 2:15 pm

nama wrote:
Wed Sep 20, 2017 1:25 pm
So I'm In NZ, and I have two ZX80's, both from the US. Neither seem to work here, but both worked when I lived in Japan. One has a composite video mod.
Is the reason they don't work have anything to do with the fact that NZ is 60hz power and the US is 50hz?

Cheers

Phil
Hi Phil

Quick answer: the ZX80 does not care if the mains power is 50Hz or 60Hz. As it uses a smoothed DC "9V" nominal supply.
However, there are (were) numinous analogue different TV standards around the world. The UK computers were designed for a 625 line, 15625Hz horizontal frequency, 50Hz vertical frequency video system. The USA uses a different system. So your ZX80s are likely configured for the USA TV system. You'll hear 'PAL' and 'NTSC' banded around, but these are actually colour encoding systems. However, if you TV has a manual selection, try the NTSC setting.

I'll give a longer answer when I have more time later...

Mark

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PokeMon
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Re: How to mod a US ZX80 to work in New Zealand

Post by PokeMon » Wed Sep 20, 2017 6:02 pm

1024MAK wrote:
Wed Sep 20, 2017 2:15 pm
You'll hear 'PAL' and 'NTSC' banded around, but these are actually colour encoding systems.
Well, the video signals are standards from the ITU, described in the ITU-R BT.470 papers (Version 6 is the latest revision). PAL and NTSC are both clever concepts of adding a colour feature to the earlier monochrome video standards with highest compatibility. So at the end you have been able to watch monochrome productions even on colour TVs as well as colour productions on older monochrome TVs without any distortion. This was a great engineering task (or let's say two). France even had a third, SECAM.

So I would say, the monochrome video signals meet the PAL or NTSC specification with just a missing colour carrier which could be treated as just optional and not required. Anyway it would be hard to find any earlier specifications than the first ITU-R BT.470-1 from 1970 (which is even hard to find at all). And nobody produces display equipment (or even chips) which does not follow the PAL or NTSC specification. And as all of these devices (or nearly all) are capable to handle a ZX81 monochrome signal, it must meet the specifications of PAL or NTSC in some way. ;)

By the way, the document covers exactly monochrome and colour transmissions as you can see in the recommendations on the first page:
recommends
1 that, for a country wishing to initiate a conventional monochrome television service, a system using 525- or 625-lines as defined in Annex 1 is to be preferred;
2 that, for conventional monochrome 625-line systems, the video-frequency characteristic described in Recommendation ITU-R BT.472 is to be preferred;
3 that, for a country wishing to initiate a conventional colour television service, one of the systems defined in Annex 1 is to be preferred.
https://www.itu.int/dms_pubrec/itu-r/re ... !PDF-E.pdf

MaFli
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Re: How to mod a US ZX80 to work in New Zealand

Post by MaFli » Wed Sep 20, 2017 7:28 pm

nama wrote:
Wed Sep 20, 2017 1:25 pm
So I'm In NZ, and I have two ZX80's, both from the US. Neither seem to work here, but both worked when I lived in Japan. One has a composite video mod.
Is the reason they don't work have anything to do with the fact that NZ is 60hz power and the US is 50hz?
I thought it was the other way around :? US 60Hz and NZ 50Hz. Could be wrong though... You can change the frequency by removing D11 next to IC10.
I bought a US version of the ZX80 a while ago and removed one leg of D11 to make it work here in the Netherlands (50Hz).

Just my $0.02 (or should I say € 0.02 :D )

*EDIT: Just did a quick search and it seems that Japan is also at 60Hz like the US. So I guess snipping or desoldering one side of D11 should solve the problem...

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