Just curious if anyone has had any luck trying to add a component video and sound hook up to a tube TV set like ctc 15,28,38 or other. I know this was afford for ctc 38 sets for special models think there called Lyceum which I have not been able to find a schematic for probably cause of there rarity. I am thinking about trying to do this but want to see if anyone else has or may have a schematic for a tube set that had this option.

While not a color set, the 23" Setchell Carson and Wollensak school tvs had video inputs. i have a Wollensak 2200 with inputs. i dont have a schematic for it though.

Not for component, only composite. Component would require extensive circuit changes, as you would be taking the demodulation section out of the equation.

You'd have to find the amplitude and polarity of the detected video signal in the set, and build a video amp to make the 1Vp-p baseband input video signal look like the one at the detector. Some color TV sets used one detector for the luma signal, and another to detect the chroma signal, both off the IF amps. That becomes harder to convert.

I had success with my Zenith 29jc20 set I got some help from my friend Danny and we made it work. It makes a better picture and seems to have eliminated interference I used to get which is bad at my present location and the tuner can be on any channel since it has been bypassed. No more need for a converter box to and if they ever bring back the VHF tuner I can put it back the way it was. Some how I doubt that will happen. The bar on the screen of the TV is from my camera in the picture I added. I may try this on a RCA next.

I did this with a BPC set, placing the CECB inside the cabinet, to act as the tuner/IF strip. And also the CECB becomes the now digital set's remote.
http://videokarma.org/attachment.php?attachmentid=171483&d=1315097178

I had success with my Zenith 29jc20 set I got some help from my friend Danny and we made it work. It makes a better picture and seems to have eliminated interference I used to get which is bad at my present location and the tuner can be on any channel since it has been bypassed. No more need for a converter box to and if they ever bring back the VHF tuner I can put it back the way it was. Some how I doubt that will happen. The bar on the screen of the TV is from my camera in the picture I added. I may try this on a RCA next.

I doubt the VHF channels will ever come back. Most of the UHF TV channels (channels 14 to 52) have been auctioned off to other services, so they will never again be used for television broadcasting in this country. The remaining 38 channels may well be auctioned in the future.

The VHF channels are no longer used for telecasting, and may well be auctioned to other services before long as well. The few FM low-power stations that operate on channel 6, for example (there is one such station in Cleveland and one in Chicago; there may be others as well) will have to cease their operations some time this year, as I think the FCC is planning to reassign the entire VHF television spectrum by the end of the year. The goal seems to be to clear the entire VHF and UHF TV spectrum of all television stations, so that the frequencies can be used for other things such as land mobile, cellular telephones and the like.


I don't know how you were able to modify your Zenith chassis 29JC20 to receive digital TV signals, unless you are using a digital-to-analog converter box feeding the set's original VHF tuner, set to channel 3 or 4.

I do not know how you managed to bypass the VHF tuner if you are using a converter, as these boxes output to either of the two VHF channels I just mentioned--the VHF tuner would have to be operational and set to one of those channels before the converter would work. I seriously doubt that these converter boxes have provisions for direct input to the IF strip, or to the UHF tuner input of the VHF tuner. The latter is the only way I can think of that the box would operate without the VHF tuner; however, even then the VHF tuner would have to remain on the "UHF" position to receive the output of the converter.

I had success with my Zenith 29jc20 set I got some help from my friend Danny and we made it work. It makes a better picture and seems to have eliminated interference I used to get which is bad at my present location and the tuner can be on any channel since it has been bypassed. No more need for a converter box to and if they ever bring back the VHF tuner I can put it back the way it was. Some how I doubt that will happen. The bar on the screen of the TV is from my camera in the picture I added. I may try this on a RCA next.

Best part of this kind of "modification" is that it is entirely non-invasive and reversible. No holes drilled, no switches mounted etc.

Good job and of course, you were rewarded wit a great picture. Thanks for sharing the information.

Pretty much all converter boxes have composite video and analog audio out. Also an easy way to connect a DVD player

Sounds like OP had mixed up terms, I though he was asking if a set can accept component inputs- not composite.

Sounds like OP had mixed up terms, I though he was asking if a set can accept component inputs- not composite.

I'm Bad!! I meant composite I got that mixed up.:scratch2:

I'm Bad!! I meant composite I got that mixed up.:scratch2:

Has anybody here figured out a way to modify an older set to take component video? I imagine that it would be much more difficult to accomplish, but even better picture quality might be obtained. :scratch2:

How about an isolated input circuit for use on "hot chassis" sets?

jr

Has anybody here figured out a way to modify an older set to take component video? I imagine that it would be much more difficult to accomplish, but even better picture quality might be obtained. :scratch2:
jr

IIRC user Tomcomm did that on his 21CT55 along with composite video, and S-video.....I would not be surprised if he tried do VGA as well.

I think you'll see the biggest jump in image quality if you can modify the set to accept "S video". That's separate luma and chroma, not mixed together. This would be non-trivial to do, though, you need to find the chroma luma separator (usually some sort of LC trap or bandpass circuit). Then you have to inject (with the right amplitude and polarity) the luma into the circuit that received the luma from the separator, and chroma the chroma.

As for hot chassis sets, an isolation transformer would be best, but be careful where you install it, to keep stray magnetic fields out of the CRT.

Adding a S-video input probably wouldn't be worth it because I don't think DVD players are commonly equipped with S-video.

I'd certainly like to know how to do composite though. That ball has been tossed around here before with no definite answer as far as I know. I saw a video of an XL-100 that someone had modified with a switched composite input, but the current owner hadn't done it.

All, but the cheapest DVD players I've seen had S-Video output on them...

I have a Toshiba SD3300. Chinese-made naturally, but not a Wally-World exclusive.

Too bad you don't live here. I can walk into a thrift shop any day of the week and grab a once expensive DVD player for under 10$ any day of the week.

I have seen no point in going to the trouble of modifying an early set for a baseband video input. I always felt the time is better spent optimizing the RF, IF and Chroma alignment. Besides I like to keep the set as close to factory spec as possible.

I haven't found a tube TV set which hasn't benefited from a sweep alignment. Even a sweep alignment check will reveal bad tubes in the tuner or IF strip which a tube checker won't reveal.

So we're about one step away from putting the flat screen inside the roundy cabinet. Modern technology must be pretty addictive. ;)

So we're about one step away from putting the flat screen inside the roundy cabinet. Modern technology must be pretty addictive. ;)

I don't see it that way at all. Gober'ment has dealt OTA a shitty hand, leaving us only flawed convertor boxes to continue using old sets. As long as the mods are easily reversible it's no worse than putting radial tires on a '69 Imperial. I don't just use my old cars for parades and I don't just use my TVs to run loops of "I Love Lucy".

To the OP, I'm curious if this solves the signal overloading and buzz issues I have with my tube sets + convertor boxes. Nothing worse than trying to show off the nice picture on your vintage set to a friend and then a commercial comes on for vaginal mesh lawsuits and the fine-print buzz makes everyone cover their ears. Or Captain Kirk looks sharp as can be, then another lawyer commercial comes on showing male breast-growth against a white background and the contrast overloads giving you a horrible picture. (Of course I find myself covering ears and eyes in these examples regardless of the TV's age)

I understand that I could use a transmitter, but that's not really practical if you want to watch TV in a room separate from the convertor box. For example, let's say my convertor/transmitter is in the living room and I decide to watch some before TV bed. Now how do I change channels? Certainly the convertor remote isn't going to reach around corners and down the stairs.

Or do I now need to get a transmitter for every room with an old TV? Just in case I'm not getting enough RF radiation and don't have enough wall-warts plugged in 24/7? A reversible mod like this sounds quite alright to me. Just a matter of a few minutes with a soldering iron and I'm back to 2009. Hardly dumping a flatscreen in a cabinet. :thumbsdn:

Thank you! This is far from gutting the set and adding a flat screen which will never happen but like you said 10 minutes or less with a solder gun and its back to 100% original since no holes were drilled or any like that. There is no buzz in the sound or signal overload on this set with this mod. and no need for that extra converter box which is nice.

I don't see it that way at all. Gober'ment has dealt OTA a shitty hand, leaving us only flawed convertor boxes to continue using old sets. As long as the mods are easily reversible it's no worse than putting radial tires on a '69 Imperial. I don't just use my old cars for parades and I don't just use my TVs to run loops of "I Love Lucy".

To the OP, I'm curious if this solves the signal overloading and buzz issues I have with my tube sets + convertor boxes. Nothing worse than trying to show off the nice picture on your vintage set to a friend and then a commercial comes on for vaginal mesh lawsuits and the fine-print buzz makes everyone cover their ears. Or Captain Kirk looks sharp as can be, then another lawyer commercial comes on showing male breast-growth against a white background and the contrast overloads giving you a horrible picture. (Of course I find myself covering ears and eyes in these examples regardless of the TV's age)

I understand that I could use a transmitter, but that's not really practical if you want to watch TV in a room separate from the convertor box. For example, let's say my convertor/transmitter is in the living room and I decide to watch some before TV bed. Now how do I change channels? Certainly the convertor remote isn't going to reach around corners and down the stairs.

Or do I now need to get a transmitter for every room with an old TV? Just in case I'm not getting enough RF radiation and don't have enough wall-warts plugged in 24/7? A reversible mod like this sounds quite alright to me. Just a matter of a few minutes with a soldering iron and I'm back to 2009. Hardly dumping a flatscreen in a cabinet. :thumbsdn:

I understand that I could use a transmitter, but that's not really practical if you want to watch TV in a room separate from the convertor box. For example, let's say my convertor/transmitter is in the living room and I decide to watch some before TV bed. Now how do I change channels? Certainly the convertor remote isn't going to reach around corners and down the stairs.


There are IR remote extenders. They have a IR receiver like a TV set that they feed to an amp and another IR emitter that is aimed at the box....Some are 2 box units that convert the remote signals to RF that travels to the second box by the device the remote is to control.

If you are handy with OP amps you could make the first type of system easily, and cheaply...The second kind would require more effort.

I honestly didn't mean any offense by that flat screen remark. I was just messin' with you guys, that's why I left the ;) I do the same kind of things, simply because we can. :)

Has anybody here figured out a way to modify an older set to take component video? I imagine that it would be much more difficult to accomplish, but even better picture quality might be obtained. :scratch2:

How about an isolated input circuit for use on "hot chassis" sets?

jr

Well, if you find the "right" DVD player it actually isn't hard at all, for B&W sets.

By "right" I mean one that doesn't bother turning off the YBR ports when its in "composite out" mode. (Older is better, usually.) Essentially the Y (Green) outputs a standard 525 line luminance signal which on modern component inputs results in "no signal" or something not all unlike a B&W set with the horiz oscillator running at 2x normal freq. Easiest way to see if you have this type of DVD player is just whack a scope on the green jack while confirming a normal picture is coming out of the yellow or S-video connection on a normal TV set.

Just shove that signal into the appropriate point on the chassis. (You may need to rig up a phase inverter, depending on if the tuner in your chassis is positive or negative sync. YMMV.)


Edit for related ramblings:

If you're going to add a baseband input to anything B&W you should always try and feed it from an S-video jack, using only the Luma signal pin (and ground, obviously.) Unfortunately a lot of things that have "S-video out" don't actually supply both discrete Luma and Chroma signals, the really cheap crap just mixes them together or duplicates the composite signal on both pins. Same can be said for the really cheap stuff with an "S-video input" on it. Usually a resistor and cap combining the signals near the jack and feeding the result to the same point as the Composite jack goes. (I do miss TVs that had properly designed/engineered comb filters.) Poke an S-video jack with a 2 channel scope sometime to see what goes on. Ideally you're supposed to have pure 525 line Luma available, which is great for pre-color sets! As above you may need to add a sync inverter depending on your chassis. (Possibly bypass a built in sync inverter, as long as its before the vertical drive pickoff, otherwise you'll not get sync.)

Its all good! No offense taken.

I honestly didn't mean any offense by that flat screen remark. I was just messin' with you guys, that's why I left the ;) I do the same kind of things, simply because we can. :)

I doubt the VHF channels will ever come back. Most of the UHF TV channels (channels 14 to 52) have been auctioned off to other services, so they will never again be used for television broadcasting in this country. The remaining 38 channels may well be auctioned in the future.

The VHF channels are no longer used for telecasting, and may well be auctioned to other services before long as well.
<snip>

The highband VHF channels (7 through 13) are extensively used for digital TV broadcasting in the US, with two of them in your backyard (Channel 19 is actually transmitted on channel 10, and Channel 8 is on, well, channel 8)

The lowband VHF channels (2 through 6) are vastly underused (your Channel 3 is actually 17 and Channel 5 is really 15), as building penetration is poor, RFI from consumer products can be intense, and the FCC placed draconian power limits on the lowband.

There are no plans to reallocate the VHF channels in the foreseeable future. They're no good for smartphones, because a smartphone can't effectively radiate waves nearly two meters long. The government is hoping to pack a bunch of other stations on the VHF channels.

At this point, there have not been any auctions of channels 14-51 for cellular. Channels 70 through 83 were given away decades ago, channels 52 through 69 were auctioned off more recently, and channel 51 is being cleared to serve as a guard band for owners of spectrum on former channel 52. The government is hoping to auction off as many of the channels 51 and below as they can, from the top down.

How about an isolated input circuit for use on "hot chassis" sets?

jr

Well, the best way IS to use the set's tuner and IF strip, and the RF output of a VCR or RF modulator. There the isolation is the small caps on the tuner's input.

As for the CECB I placed inside a TV I did, I used the audio and video output jacks of the CECB to feed the baseband video into the video circuits of the TV, and the audio to audio. For this set, it was easy, as this set used to have a built in VCR that died.

I would be interested in hearing from anyone else who attempts a similar mod on a tube-type TV set of any kind. I would like to do this on several of my sets mainly because the modulator is one more box and one more power brick, and because a direct connection will give a cleaner signal. I've seen success here with an early Zenith color set, and Phil Nelson's site documents a composite input on an Admiral B&W set, that's two that I know of. My understanding is that some sets may require a signal inversion or a gain stage, so it would be interesting to document that somewhere. Has anyone successfully added a composite input to an RCA?

It is not all that hard to figure out. With a sam's one can look for a video injection point after the video detector, and before the synch take off. Then just observe the waveform amplitude and polarity there on the schematic or in the set with a scope. with that data and the google info on the composite video signal standard one can figure out the gain needed. And then all that is needed is a simple OP amp circuit that ANYONE can design for the specific gain and possibly polarity inversion required for nearly any set. The OP amp could be powered by rectified heater voltage on transformer powered sets, though if the output amplitude is large one might need to use a voltage doubler, trippler, etc to get enough rail voltage for the OP amp....Not to mention the many other power sources both set derived and tacked in that could be devised.

though if the output amplitude is large one might need to use a voltage doubler, trippler, etc to get enough rail voltage for the OP amp....Not to mention the many other power sources both set derived and tacked in that could be devised.

Lets not forget the fact that these are all high impedance circuits. You could just make an "unun" transformer. So you have 1v p-p composite in, and you need 10v p-p out? 1:10 matching transformer. Phase inversion is easy if you use a 1:1 isolation transformer (There are many made just for video.) and flip the output phase. You can also combine both. Invert the phase and derive 5v p-p baseband via a swapped output 1:5 ratio unun.

That's a good idea, and I guess that raises another question that I hadn't thought of. Does the composite input need to have a 50 ohm termination? I haven't worked with video inputs very much, so I'm not sure what would work best. The unun transformer is a good idea, it might also be useful for a hot chassis set. Without some form of isolation, I don't think it's a good idea to add such an input to a hot chassis set.

That's a good idea, and I guess that raises another question that I hadn't thought of. Does the composite input need to have a 50 ohm termination? I haven't worked with video inputs very much, so I'm not sure what would work best. The unun transformer is a good idea, it might also be useful for a hot chassis set. Without some form of isolation, I don't think it's a good idea to add such an input to a hot chassis set.

75 ohm termination is good engineering practice for CVBS. That was a very good question to ask. Means that you're understanding things. :thmbsp:

I had success with my Zenith 29jc20 set I got some help from my friend Danny and we made it work. It makes a better picture and seems to have eliminated interference I used to get which is bad at my present location and the tuner can be on any channel since it has been bypassed. No more need for a converter box to and if they ever bring back the VHF tuner I can put it back the way it was. Some how I doubt that will happen. The bar on the screen of the TV is from my camera in the picture I added. I may try this on a RCA next.

I'm about to try this on my 29JC20 as workaround for it's alignment issues. If I get stuck do you have any schematics marked up with the mods? Also are the coax leads all you did?....I'd presume something was done to disable the RF system like removing B+ or IF leads from the tuner or removing the tube prior to the first signal injection point.

I think you'll see the biggest jump in image quality if you can modify the set to accept "S video". That's separate luma and chroma, not mixed together. This would be non-trivial to do, though, you need to find the chroma luma separator (usually some sort of LC trap or bandpass circuit). Then you have to inject (with the right amplitude and polarity) the luma into the circuit that received the luma from the separator, and chroma the chroma.

As for hot chassis sets, an isolation transformer would be best, but be careful where you install it, to keep stray magnetic fields out of the CRT.

This was from a thread, I thought was yours:scratch2:187919

This was from a thread, I thought was yours:scratch2:

http://www.videokarma.org/attachment.php?attachmentid=187919
That will work to create composite video that will have minimal cross luma into chroma errors in a notch filter color TV set. If the TV set in question is a notch filter set, the luma bandwidth that you see on the CRT screen is low pass filtered to avoid the appearance of the chroma subcarrier (a crawling fine grain checkerboard pattern atop highly colored areas of the image).

True S video would produce about twice the resolution than the above composite video maker. But this composite video lets you not need to dig deeply inside the set's color circuits.