Bought an HDTV receiver box today and TV modulator to feed vintage TV sets

[wa2ise]

That's nice you say but what's the vintage TV connection?

Well, it has an Svideo output jack that I used an Svideo cable with the luma signal peeled off feeding the TV modulator to feed my 1950 Admiral bakelite TV set. Rason for that is that I can feed that TV a B&W signal without the chroma subcarrier, which in a B&W TV this old will show as a crawling checkerboard pattern. So I can watch live broadcasts (like a football game) on the B&W set as if it were a B&W broadcast before color TV was established. And the HDTV box, a Samsung, has HD rate video outputs at the same time it makes the Svideo regular TV signal.

A satellite TV box, or a digital cable box with an Svideo output jack will also let you do the above. So this is what you'll have to do once NTSC terrestrial broadcasts stop in a few years.

[nasadowsk]

So, what's the picture like?

[polaraman]

YES! Pics please!

polaraman

[Charlie]

Interesting! You're saying you modified the cable to get rid of the color?

[oldeurope]

Good evening,
I found an other way to solve your problem.
Look there:
http://www.vintage-radio.net/forum/s...ead.php?t=6753
If you want I can explain it in a new thrad.

Kind regards
Darius

[Eric H]

My old SD Satellite box had an RF output that worked fine with most old sets, the new HD box doesn't so it looks like I'm gonna need this!

Is this cable something available or did you modify an existing cable?
Can you post the details for those of us in the dark on Svideo? (besides just being able to plug it in )

[wa2ise]

Here's a diagram (and a better quality attempt to photograph the B&W TV and HD display on a VGA monitor) showing how to split off the luma video signal off a S video cable connector and to feed it to a TV modulator. Luma video on an Svideo cable is just like a composite video signal (75 ohm impedance, 1V peak to peak when terminated by 75 ohms) so the TV modulator will be happy.

[Jonathan]

I purchased a crappy RF modulator from Rat Sh*t Shack. If there is an inseries component with the chroma signal, remove it, or you can unsolder the S-video connector and snip the chroma pin. The picture does not do the justice, as it looks awesome.

Jonathan

[southernguy]

Has anybody tried feeding there HDTV receiver box into a B&W set with it being set to 1080i using the green Y RCA jack. I tried it once to see what it would do. The horizontal hold had to reajusted to achive sync, but as a result I got 2 pictures side by side on the screen. Of course an HD roundie would be pretty cool. I wonder if anybody has ever though about that and would it work.

[blue_lateral]

Originally Posted by Charlie

The colored RCA jacks (green, blue, red) are labled Y, Pb, and Pr. Since this DVD is currently connected to my CM roundie, I unplugged the RCA Video Out (yellow jack) and plugged in the RCA component Y (green jack). PRESTO... A perfect black and white picture!

I've wondered about that but never tried it. I have read that most of the interference comes from the color burst, but this method would also remove the chroma information from the video. I think after color was common, they just built b/w sets with no high frequency response in the video amplifier to avoid the chroma interference. On older sets capable of a really sharp b/w picture, the interference would be worse.

wa2ise- How is the overall quality of the video? There is no over-the-air HDTV where I live yet. The quality of over-the-air analog here is pretty bad. I had high hopes that HDTV converters would finally be a high-quality signal source for these older sets. There is another thread going that suggests the quality is terrible. What do you think of yours?

John

[wa2ise]

Originally Posted by blue_lateral

I've wondered about that but never tried it. I have read that most of the interference comes from the color burst, but this method would also remove the chroma information from the video. I think after color was common, they just built b/w sets with no high frequency response in the video amplifier to avoid the chroma interference. On older sets capable of a really sharp b/w picture, the interference would be worse.

wa2ise- How is the overall quality of the video? There is no over-the-air HDTV where I live yet. The quality of over-the-air analog here is pretty bad. I had high hopes that HDTV converters would finally be a high-quality signal source for these older sets. There is another thread going that suggests the quality is terrible. What do you think of yours?

John

Hi John, the quality of true HD is excellent, but the source at the TV station has to be excellent as well. Sports events like the SuperBowl are usually excellent, but other material recorded at low resolution will never look good. If you can get HDTV over the air reception the quality of the image will be great. But there is the "cliff effect", either you get perfect images or nothing at all. Oh, there is a narrow region between the two, where you'll see the image literally break up and studder, but no ghosts.

Sure you have no HDTV service in your area? Most over the air NTSC stations have HD service that covers substantially the same area. But if your NTSC reception is poor, you might not have HD either. But most HD is transmitted in the UHF band, and a highly directional high gain UHF antenna might bring in the HD, as well as your NTSC UHF stations. If you can get decent NTSC that way, the HD should work.

There's always cable HD and satellite, but those cost subscription fees. Also be aware that digital cable and satellite use different transmission standards than over the air uses. So an "over the air" box won't work on cable or satellite.

As for the use of the "Y" green RCA jack on the HD receiver box, that will work *IF* you setup the HD box to convert all digital reception to "480i". My box provides NTSC (composite and S video) on separate jacks from the VPrPb high def jacks at the same time.

You could convert an old roundie to display HD, but you'd have to modify the horizontal deflection circuits to operate at 32KHz (1080i) or 43Khz (720p). This is not trivial. Especially when you consider the convergence and pincusion circuits (for a color roundie of course). Also the video amps would need more bandwidth. But for a B&W roundie all you really need do is change the timing circuits of the horizontal oscillator. A potential problem is that the B+ boost and the very high voltage may change too much (duty cycles would be different) You'd have a lot of overscan, but that's not serious in that the display area is 4 by 3 instead of 5 by 3. But you'd need extensive TV experience to pull it off successfully. As for a color roundie, this is a case where pulling the chassis (and storing it for later use in a restoration) and installing a VGA monitor's CRT and circuit boards in place of it would make more sense. If it's an older one with real pots for contrast and brightness you could remote those pots where similar ones served the old chassis. You should be able to reuse the old tuner to then feed its IF into the IF of the HD receiver box (which you'd also hide inside the console) so it would still work as normal. A tube audio amp (fed by the same power supply you'd build for the tuner) could be used to keep that "tube" sound the old chassis had. Using the same volume control from the old chassis. So it could be done, might as well use that nice old cabinet that is missing the old CRT or chassis...

[Jonathan]

Charlie had a great idea I never thought of. The luma output from component video output will produce a nice b/w picture, very sharp, but as long as it's 480i. I use S-video on all of my dvd players, satellite boxes, etc. so using the luma from the green RCA jack is perfect. I still need to figure out a way to strip the chroma from a composite video signal, for the boxes that I can't use the s-video and Y output at the same time.

Jonathan

[andy]

...

[RetroHacker]

Originally Posted by Andy

Removing the chroma from a composite video signal is not at all easy. It's like unscrambling an egg. Even a sophisticated digital comb filter that compares several complete frames of video can't do it perfectly.

It can't be all that hard - I was under the impression that composite video was two seperate signals, tied together, but at somewhat different frequencies - it would be a matter of 'tuning' in the right one.

Besides, I was at Rat Shack yesterday, and saw a little box that converts composite video to S-Video. Actually, it was meant for converting video and audio - it converts composite to S-Video, and analog stereo audio to digital PCM audio. It was a little bitty box, about the size of a deck of cards, and was marked down to $3.74 or something like that. I was probably on clearance because of the utter uselessness of converting analog audio to digital PCM... Think about it, if you've got hardware that takes digital PCM, it also takes analog audio, and the point of converting it somewhere else is moot - it's not gonna sound any better... But hey, the box could be used just for the video, if you had an application where you wanted to filter the chroma and luma from each other.

-Ian

[wa2ise]

Originally Posted by andy

Removing the chroma from a composite video signal is not at all easy. It's like unscrambling an egg. Even a sophisticated digital comb filter that compares several complete frames of video can't do it perfectly.

I used to do research and development at RCA Labs years ago on this problem. It is very hard to do it well. A reason that we get away with imperfect separation is that the portions of the luma image and of the chroma subcarrier (in terms of areas of the image on the CRT screen) track each other, and that our brains can pretty much ignore the crosstalk. Now if the two signals were unrelated, the crosstalk would be much more objectionable.