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Vintage Television and Video Vintage television and video equipment, programmes, VCRs etc. |
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24th Sep 2008, 7:29 pm | #1 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Colour CRTs suitable for NBTV
Hello all,
Please can I pick the brains of all the telly experts... I've managed to get sidetracked whilst building my latest NBTV creation into the realms of colour. I've "invented", well thrown together, some software to produce a colour compatible 32line NBTV/NTSC standard and a recorder and playback software. [read about it here] I still can't believe it works! The whole thing fits into a 20kHz bandwidth too! I'd now like to actually make a receiver of some kind. Eventually I'd like to build a mechnical viewer but in the meantime I'd also like to try and botch together something using a small colour CRT. Trouble is I've no idea where to start, I'm hoping with the combined wisdom of the group I might be able to get something up and running quickly... If I get a small relatively modern colour portable or small computer monitor and use the CRT: Will I still need thousands of volts on the anode or is there any way to "underrun" them: this works ok on monochrome tubes but I'm guessing that modern aperture grille CRTs won't converge? If I can underrun the anode will this reduce the amount of juice I'll need to run the scan coils? If I still need the full EHT would it be possible in a relatively straightforward set to still run the LOPT circuitry without the scan coils connected? I could then leave the set running as normal for the EHT/Focus but hijack the scan coils/grids/cathodes of the CRT? Any hints, suggestions, references to a decent psychiatrist would be very welcome. Dom |
27th Sep 2008, 9:39 pm | #2 |
Heptode
Join Date: Jul 2003
Location: North Walsham, Norfolk, UK.
Posts: 516
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Re: Colour CRTs suitable for NBTV
Hi i would track down a little battery portable with a 5" screen the ones with narrow scanning . thay were also available with radio cassette recorder built in you will then need some dummy coils to replace the line coils so the line timebase is still operative then you can do what you whant with the coils that are on the tube . next locate the video driver transistors and again you can easily highjack the video at the bases. it is possible to build the hole thing from scratch with valves. but you will still need the high eht and focus voltages . Danny
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28th Sep 2008, 7:01 pm | #3 |
Dekatron
Join Date: Dec 2007
Location: Haarlem, Netherlands
Posts: 4,199
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Re: Colour CRTs suitable for NBTV
Under running will probably affect focussing more then it will affect convergence. I wouldn't reccomend it.
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28th Sep 2008, 10:08 pm | #4 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Re: Colour CRTs suitable for NBTV
I'd probable want some level of de-focusing, either by deliberately defocusing or by some kind of "dot-wobble".
Either way, I've been having a good look round on e-bay and the only mini-CRT thing I've found was quite expensive... Dom |
1st Oct 2008, 8:37 pm | #5 |
Retired Dormant Member
Join Date: Jun 2007
Location: Herongen, Germany
Posts: 65
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Re: Colour CRTs suitable for NBTV
I would not use a CRT at all, but a mirror-drum or a Nipkow-disc and LEDs. No high voltage, and no problem with 32 lines on a colour CRT made for much more lines. If you prefer a CRT why not a black and white CRT and a rotating colour-wheel?
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1st Oct 2008, 11:14 pm | #6 | |||
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Re: Colour CRTs suitable for NBTV
Quote:
Quote:
Quote:
Cheers Dom |
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2nd Oct 2008, 12:25 am | #7 |
Retired Dormant Member
Join Date: Apr 2005
Location: Reading, Berkshire, UK.
Posts: 95
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Re: Colour CRTs suitable for NBTV
I think DrZarkov is on the right track.
You can get high power (over three watt) RGB LED's.. And I can tell you that they are really bright. I have used them to expose optical soundtracks on film. I found that I could set up a colour, and it would be pretty stable. I haven't tested them for linearity/tracking regarding modulating them. But IMO it is worth a go.. Trish |
2nd Oct 2008, 9:06 am | #8 |
Octode
Join Date: Nov 2004
Location: Hebden Bridge, West Yorkshire, UK.
Posts: 1,885
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Re: Colour CRTs suitable for NBTV
Yes, I agree: I've just received a nice Nipkow disc and I've just ordered a load of LEDs and I'll be trying various different types out. The ones I've just ordered are superflux ones, nice and small but aparently quite bright, if those aren't bright enough I'll try bigger 3W ones but would prefer many small rather than few large so I can get a nice overlap of red green and blue.
However that's likely to get is into trouble for being off topic - I still want to build a CRT NBTV receiver, not for any good reason other than (to see if) I can. I've a few other ideas where I'd like to try underrunning (in both terms of line/frame frequency and EHT) or otherwise "misusing" colour CRTs. Thanks Dom |
15th Nov 2008, 3:25 pm | #9 |
Retired Dormant Member
Join Date: Apr 2005
Location: Reading, Berkshire, UK.
Posts: 95
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Re: Colour CRTs suitable for NBTV
Apologies for raising this thread from the depths.. I found some interesting items during a search for something completely different about my local Radio club..
It might be worth some more research.. I have to admit that I hadn't heard about the Narrow-bandwidth Television Association until now.. ---> 30 Line Television ---> Amateurs Turn Back the Clock on Television Technology Trish |