connecting to Digital TV

For experts to discuss very technical stuff and newbies to ask why the Spectrum they bought off ebay doesn't work.
denjerus
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connecting to Digital TV

Post by denjerus » Sat Mar 17, 2018 12:25 pm

Rummaging through my underground Attic I rediscovered about 300 old Spectrum games, 3 old 48K spectrums and a Spectrum128+. There was original power packs for both models and they have good outputs. I connect the tv output to the coax socket on my digital tv but of course, (stupid me) i surely need the tv to be an analogue device. Or do I?
Haven't used the speccy for years of course but I used to add titles to my videos way back when. Still have the video interface plug ins and programmes to do the effects, and was curious to see if they still work.
The 48K models don't beep when they are powered up but 128K plus model does gently warm up the heatsink after a while, but without the output I can't tell.
Is it worth persuing the resurrection or should I just flog off the software, (some of which seem to have some value)?
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PeterJ
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Re: connecting to Digital TV

Post by PeterJ » Sat Mar 17, 2018 1:07 pm

@denjerus You can buy a SCART cable from Retro Computer Shack for the 128 which will give you a good picture on most modern TVs.

https://rover.ebay.com/rover/0/0/0?mpre ... 0949446667
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denjerus
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Re: connecting to Digital TV

Post by denjerus » Sat Mar 17, 2018 2:34 pm

Thanks PeterJ. I've ordered that after faffing about all day with boxes of connectors that would surely "come in Handy" but didn't.
Then lets hope it will work. Thanks for the quick response. I had looked on ebay but obviously searche for the wrong thing. Thanks Again, I'll let you know if it works.
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denjerus
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Re: connecting to Digital TV

Post by denjerus » Wed Mar 21, 2018 11:29 am

Well I got the lead, Very quick delivery considering the weather we've had. Unfortunately my TV screen is mostly Black but you can discern the Black border around the black stiped central portion that visuals used to appear in. Looks like time has taken its toll on the innards The heatsink has warmed up and I've left it turned on for a while to dispel any moisture in there, but it looks terminal from here, Any thoughts??
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Ast A. Moore
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Re: connecting to Digital TV

Post by Ast A. Moore » Wed Mar 21, 2018 12:52 pm

Is it the 128k machine? If so, then the TV expects a composite signal but receives only the vertical sync. If you can manually select RGB on your TV, do so. If not, there are two options. One is to use the composite video output from the Speccy. The other is to feed a suitable voltage to the BLANKING pin on the SCART connector, which is not as straightforward.
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MatGubbins
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Re: connecting to Digital TV

Post by MatGubbins » Wed Mar 21, 2018 1:01 pm

It is possible that the digital TV is not compatible with the lead. Some digital TVs don't lock on to the signal or have a jumping/flashing image. My Samsung is fine with the lead, my Matsui is hopeless so it has the composite signal instead and works fine. If you have a few TVs to test with then give each of them a whirl.
The 128 machine can be tested by plugging in a set of headphones into the ear/mic socket, press a few keys (not Enter) and if you hear click via the headphones then the machine is working, just need to get a steady picture output.
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Guesser
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Re: connecting to Digital TV

Post by Guesser » Wed Mar 21, 2018 1:50 pm

It's because the Spectrum 128 isn't compatible with SCART without modifications (or a powered RGB-SCART cable)
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Ast A. Moore
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Re: connecting to Digital TV

Post by Ast A. Moore » Wed Mar 21, 2018 3:02 pm

Guesser wrote:
Wed Mar 21, 2018 1:50 pm
It's because the Spectrum 128 isn't compatible with SCART without modifications (or a powered RGB-SCART cable)
Some TVs (mine, for instance), allow you to manually choose between RGB and composite video inputs on the SCART connector. I still wired my cable with composite video on pin 20, rather than vertical sync. It’s fun to switch between RGB and composite and compare picture quality. :D But mostly to freak people out by playing this (wink-wink, nudge-nudge). ;)

P.S. A button-cell battery inside the SCART connector might also do the trick in the short term, though the easiest way to go is to feed the required 1–3 V to pin 16 from inside the TV itself.
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and zasm Z80 Assembler syntax highlighter.

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Re: connecting to Digital TV

Post by Guesser » Wed Mar 21, 2018 3:40 pm

Ast A. Moore wrote:
Wed Mar 21, 2018 3:02 pm
I still wired my cable with composite video on pin 20, rather than vertical sync.
That is the correct wiring, SCART wants a composite sync or composite video. The 128 only provides separate horizontal and vertical syncs.
Ast A. Moore wrote:
Wed Mar 21, 2018 3:02 pm
P.S. A button-cell battery inside the SCART connector might also do the trick in the short term, though the easiest way to go is to feed the required 1–3 V to pin 16 from inside the TV itself.
A coin cell won't last long at all driving the blanking pin, on the order of a few hours. I wouldn't say modifying the TV is easiest, better to make a passthrough cable for the 9v supply feeding a suitable resistor. (Not sure why RGB cables for the Spectrum 128 don't come like this already frankly)
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Ast A. Moore
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Re: connecting to Digital TV

Post by Ast A. Moore » Wed Mar 21, 2018 4:49 pm

Guesser wrote:
Wed Mar 21, 2018 3:40 pm
The 128 only provides separate horizontal and vertical syncs.
Oh, sorry, I misspoke. I meant composite sync, not vertical sync. But since the composite sync is already present in the full composite signal, I decided to go with the latter. (I originally wired the composite sync signal; then after trying out Chromatrons, I decided to leave go with the full composite signal. Tons of fun!)
Ast A. Moore wrote:
Wed Mar 21, 2018 3:02 pm
A coin cell won't last long at all driving the blanking pin, on the order of a few hours. I wouldn't say modifying the TV is easiest, better to make a passthrough cable for the 9v supply feeding a suitable resistor. (Not sure why RGB cables for the Spectrum 128 don't come like this already frankly)
Ha! A passthrough power supply cable is an excellent idea. Hadn’t thought of that. For me, though, that’d be more fiddly than the simple TV mod (primarily, because I’d need to source a male 2.1 mm plug + female socket, and cobble together something of a neat enclosure for them).
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Every man should plant a tree, build a house, and write a ZX Spectrum game.

Author of A Yankee in Iraq, a 50 fps shoot-’em-up—the first game to utilize the floating bus on the +2A/+3,
and zasm Z80 Assembler syntax highlighter.

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