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Sinclair ZX Spectrum

DarthKur

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..In Europe and other PAL areas, it is quite common that the slightly more expensive TV sets can display a NTSC RGB/composite signal (not RF/antenna though). I've understood that the opposite is almost unheard of in e.g. the USA?


Multi-signal sets do exist but they are quite uncommon and never advertised.
 

DarthKur

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I was thinking a cheap alternative would be scart to rca/s-video adaptor and a pc tuner (PAL/NTSC) like This..

It would be great for setting up on a laptop, if one is around.


Hmm, that's an interesting gadget. I wonder how that well that would work. Sadly, none of my "modern" pc's possess all of the specs that it requires.
 

ljones

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Feb 12, 2008
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I've got one of the old rubber-key speccys here, as I am in the UK. The ZX spectrum never had any sort of video out from memory, all it offered was a basic UHF output at channel 36. I'm guessing to get any better there are only 2 options - one would be to hunt down a multistandard VCR (some new VCRs in the UK can accept an NTSC signal; I don't know if new VCRs in the USA can accept a PAL signal). Only other way would be to tap off the signal from the RF modulator and feed that into something like a video to VGA converter.

ljones
 

tezza

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I've got one of the old rubber-key speccys here, as I am in the UK. The ZX spectrum never had any sort of video out from memory, all it offered was a basic UHF output at channel 36. I'm guessing to get any better there are only 2 options - one would be to hunt down a multistandard VCR (some new VCRs in the UK can accept an NTSC signal; I don't know if new VCRs in the USA can accept a PAL signal). Only other way would be to tap off the signal from the RF modulator and feed that into something like a video to VGA converter.

ljones

The one (old rubber-key speccy) I have has a RCA connector on the end of a long thin cord which disappears into the machine via a tiny hole cut next to the UHF output. If I plugin this into to a standard video RCA jack on the TV I get a nice clear signal. It's a homebrew mod. Someone's obviously figured out how to by-pass the RF modulator and so just allow for composite video.

I haven't opened the case up to see exactly what they have done though.
 

carlsson

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The rubber-key ZX Spectrum is relatively simple to modify to output composite video instead of RF. It is about desoldering one resistor, cutting one wire and rewiring another one, if I remember correctly. With a proper instruction, it should take less than 30 minutes for someone with average soldering skills. I have done that to my own Speccy.

Whether PAL composite video is easier to receive on a NTSC TV (or vice versa) than PAL RF signal, I'm not sure. But I know more PAL TVs can display a NTSC composite video signal than they can display a ditto RF signal.
 

BrunoFlorindo

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As a fanatic Portuguese Spectrum user, I too had to overcome the difficulties of using UK computers here. This is how I solved it:

For the 48K model I had the composite mod made and I power it with a Radio Shack 9v adapter. The original TV out is now an RCA video out.

For the 128K and 128K +2 models I use the same adapter and have an RGB-to-RCA cable.

For all the other models (+2A, +2B, +3) I use an external hd adapter but the original connector was replaced by the one the Spectrum uses (a din-style plug). This provides me all the voltages I need except the -12V which is only useful for the Amstrad Spectrum's RS232 port. The RGB output on these models isn't the same because it's missing a chip, thus rendering my RGB-to-RCA cable useless. There is a way to fix it, but it requires an internal mod.

With the power and video output problems solved, I still had to find a way to display the PAL video. Instead of buying expensive converters, multi-systems TVs or dozens of cables, I bought a capture card with european-style TV input (less than $20 including shipping), installed the bt878 drivers from Sourceforge (free) and installed Dscaler to display the captured video in real time (free). I'm happy with my setup, but I couldn't do it without help. :)
 

Albert

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Oct 31, 2010
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Hi, I was mucking around Google, trying to find if anyone had done anything similar to this, and this thread just happened to be near the top. I wanted to ask just a couple of questions, even though this thread is dreadfully outdated (Oh well, most of the 00's were a blur, anyhow...):

1. Is it possible to use this to convert a ZX spectrum power supply to a US plug?

2. Can I use this for video conversion, or is it possible to use one of those region-free DVD players. And is it possible to modify the ZX Spectrum to handle higher quality video output, and then use a PAL to NTSC converter?

Thanks,
Albert

PS: I have been hoping to get a ZX sometime the end of this year, but it is terribly hard to find one on Ebay. If anyone would like to contact me, offering me a 48k, I would be willing to pay anything at around 40 USD (w/ shipping). Thanks again...
 
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carlsson

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1. Yes, the power converter you found looks to be a step-up converter that will take 110-120V and output 220-240V. However if you already have a switched DC power adapter with reversible polarity, you don't need a power converter for the ZX Spectrum. You should be able to feed it 9V DC, center negative polarity directly from a 110V adapter. The step-up might be nice for other equipment though, those with a power supply built into the machine.

2. The video converter would work if you internally modify the ZX Spectrum from RF to composite video output. It is a relatively simple process although it involves soldering. A caveat is about signal strength though, the resulting signal is strong enough to drive all the TV's and monitors I have tried but theoretically it might not be a 100% signal.

As for higher quality video, in theory you should be able to get RGBI from the expansion port but I don't know what it takes to convert it to a meaningful signal. I think you would need to build a couple of voltage dividers to bring the signal from potentially TTL levels to 0.7 Vpp which is what e.g. SCART equipment in Europe expects. In your case I don't know what device you would feed the signals into.
 

Albert

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This is well beyond my knowledge (I don't know soldering, or circuitry, or programming of the such), but I've been scouring eBay and finding these RGB to pal/ntsc encoding chips, and other types of encoding chips for dish repairs and such. This may or may not be common knowledge, but it can't be denied that someone, somewhere has created a homemade converter of sorts, that is cheaper and has a wider range of support than these simplistic Chinese ones I've found, already.

I'm not desperate, I could save up cash and buy a multisystem TV. It would just be nice to broaden my horizons, and put my soldering iron to good use (or a breadboard). That, and I'm just a bit stubborn, most times. :p


On the matter of power, I think I'll try and use a 220v-110v adapter first, then I'll go with the 9v idea. Also, I'm certain that I've read on how to modify the ZX to output to ntsc. Just gotta find it...

UPDATE: Ah, wait! Does this article nix my encoder idea? In that I could simply modify the ZX, and it'd output to a NTSC television, problem-free?
 
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carlsson

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The article describes the composite video mod I've been referring to. It will make the ZX Spectrum output PAL composite video, which your equipment might be capable of inputting as it is, but possibly only B&W. The converter you linked to would convert the 625 line, 50 Hz PAL signal to a 525 line, 60 Hz NTSC signal. I don't know to what extent you risk that graphics will look squashed or blurry but in any case, composite video is so much nicer to work with than RF even if the signal would not have full strength.
 

Tupin

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Big bump, I know. But since I've always wanted one of these but have been turned off by the tools required to get it to work in the USA, I have a question.

I could take a 9v, 120v power supply with center polarity and it would work? I thought it needed 240v.

If so, if anyone would like to sell me a 48k system without the power supply, I would be interested.
 
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carlsson

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As far as I'm concerned, 9V DC is 9V DC all around the world. There is not even a phase involved as it would be with AC. For that matter, I have powered an NTSC VIC-20 with an European power supply perfectly fine. I believe the RF or modified composite video signal would be a bigger hurdle for you than the power supply. It is much more complex about computers with the power supply built into the machine.
 

Tupin

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Well, I would plan on doing that RCA mod which would give me composite video but without color, which would be fixed by a converter.
 

deathshadow

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Back when I had a zx-81 (some three decades ago) one of the first things I did was order a replacement TI 99/4A keyboard. The wiring for most of the key-rows was the same, though the columns took a bit of reworking to build the correct keyboard matrix... thankfully the traces and solder points were all exposed on the bottom so rewiring was a snap with an x-acto and some bus wire. It was common practice on a lot of the old membrane and chiclet keyboard systems to adapt keyboards from other machines because they sucked so bad. The ONLY thing the old systems like the Spectrum had going for them were they were cheap... At a time where a level one basic Trash-80 model III would have set me back the cost of a new car, I was able to buy a ZX-80 kit for $199 USD.

Was always hard to say which was worse -- membrane keys or chiclet. It's why I laugh at the PATHETICALLY USELESS chiclet mac keyboards -- it sucked thirty years ago on the Coco, it sucked twenty-nine years ago on the Spectrum, it sucked twenty-seven years ago on the PC Jr., it sucked 26 years ago on the C=116, it sucked 25 years ago on the Enterprise 64... and frankly it sucks today on the netbooks that do it, and it sucks when Apple does it too.

But of course, Apple's reality distortion field prevents any of their rabid kool-aid drinking fanboys from actually noticing it...
 

carlsson

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Is 300mA enough?
No. You will need at least 9V, 800 mA to power a ZX Spectrum. If you want to add any peripherals, you should aim at 1.2A or above. Please remember the Spectrum needs center negative polarity. If you use an universal AC adapter that has switchable DC output and different plugs, each plug can be rotated to match the proper polarity.
 
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