Wanting to tap the rgb port
 

Hello,

First time poster here. I was referred from the Facebook group the CRT Collective. It's a 1989 Zenith System 3 Digital.

I bought this tv from a fellow member there and it has an rgb port on back. I was wondering if anyone knew how or what is needed to use it. I'll include some pics. Any help appreciated
Thanks!

I'd assume it'd be for connecting one of them new-fangled 'personal computors,' especially since the next one over says Text Print. But it's quite odd that it's a card edge connector. I'd imagine it uses a fairly standard VGA style signal, but I have no idea. Look up at the connector from the bottom and see how many pins it has. I'd wager 10.

Sweet set! Love the lighted keypad. A service manual should have the info you need.

Any clue where I could find one of those manuals?

I was hoping to see what all the rgb hype was all about. I have a snes I was wanting to hook up.

I'll try and get a closer look and see how many pins there are.

Also I aplolgize, I did not realize the pictures posted in the orientation they did.

Even though it's a digital TV, I'm sure it's an analog input. Zenith was big into PCs at the time and had a proprietary cable to plug in.

I'm guessing that the text print port means that this set has a Teletext decoder.

I can't recall what the RGB port would be on these. There's a good possibility it's not compatible with anything current; for example, it could be TTL logic levels.

Maybe somebody who knows for sure will chime in.

One of the people that worked in the same place I did had one of those sets and he even bought the printer that was available for that set.
He was the biggest toy and trinket buyer, I ever knew!

Wow yours still has a sweet pix. When they came out the table
model was $1100 & we sold it $1000 with a free printer.
Teletext was just a newspaper format & also used by truckers to
find loads. It was sent by the Atlanta superstation on cable.
The set was NTSC. After video & audio detect everything was digitally
processed then back to analog for the outputs. I dont remember
the RGB but probably TTL. Look for an owners manual, OEM service
manual, training manual or Tech Topics for more on it.

One thing I would do to this set is recap ( lytics only) the vert board. A bad
cap will blow the IC. The IC has been disco for YEARS.........

73 Zeno:smoke:
LFOD !

...

I have a Zenith SMS1917SG 19" table model TV (new in 1995) which has a Teletext decoder, but no printer port or RGB port. I never used the decoder, although I might have seen teletext activity through that system had I been in the Atlanta area. I think WTBS-TV (channel 17) in that city was experimenting with teletext in the late 1980s-early '90s. The teletext decoder in my Zenith TV has two modes, Text 1 and Text 2, selectable from an onscreen menu; I think text 1 was standard teletext, but I am not sure what the second TT option would have been used for. In any event, since my area's TV stations were not conducting teletext tests or using the system at all (I doubt they were), I never knew if the TT decoder in my set worked or not.

While my set has the teletext option in the OSD menu, however, I am not sure if the decoder would have been usable since there are no RGB or printer ports on the back of the set; the only input jack there is a 75-ohm connector for antenna or cable TV. Since the set has no RGB or printer ports, I can't help but wonder why the TV had a teletext decoder in the first place, unless it was designed only for on-screen readout, the RGB/printer ports were available as extra-cost options, or if there was a special model of this TV that indeed had the ports built in. :scratch2:

Thank you all so much for the responses. Looks like there are 7 pins on that edge connector from what I can see. I will also certainly look into a recap, don't want anything happening to this ole thing. It seems to work well. Not sure how hard or how much it was used. But I'm pry correct in assuming this was zenith top end back in that time, yes?

Teletext use was expected to mainly be on-screen, with printing used infrequently, much like a modern internet service. In Chicago, where Zenith was located, the service from Atlanta was broadcast. For a while, there was a long-haul trucking jobs listing service, and it was intended that teletext receivers would be installed at major truck stops so independent truckers could bid/apply for runs (I'm not sure exactly how it worked). Another service was intended for home use and had things like news summaries, horoscopes, recipe of the day, and so on. I had a Zenith rear projo with Teletext at home, and would call the service sometimes to request a particular recipe to be posted, or answer the day's puzzle. The broadcasts in Chicago also contained test pages of repeating characters that made the clock recovery particularly difficult. One of these was titled something like "Page for Gary." Gary was an engineer at Zenith working on Teletext. The page stayed up long after the attempts at commercial service died, until Teletext was removed entirely.

PS: Teletext coding was at a low data rate, intended to be relatively ghost-resistant without requiring a ghost correction circuit in the receiver.

Zenith , Sony & RCA were considered the best by most.
IIRC the digital chip set was made by ITT. I have seen it used. also in Toshiba,
& NEC sets. Also probably was in MGA & Panasonic but I have only seen the
manuals. Zenith by far built the most of them. It came in 19" or 20"
( dont remember which ) 27" & projo's. Also some had Bose audio
& there was an amp only option. Awsome sound !

Yup it was WTBS that carried text. Zenith also owned a Chicago UHF
but I would guess that was sold off years before.

JEFFHS.
Your set is interesting. The model hints at it being an institutional set.
Also 19" was rare then. If you ever can we would LOVE to see some pixs
of it & nudies.

73 Zeno:smoke:
LFOD !

Edit: Starting separate thread

Edit: Starting separate thread

Here are some pics of the inside on mine. It's actually cleaner than I expected. The main board on the bottom has a cover over it. Where should I begin about recapping?

Starting separate thread

Only recap the sweep board & only the electrolytics. Also check
it real good for cold joints.
The big shielded board on the bottom is the digital board. Do not
mess with it unless you HAVE to.
RGB is probably TTL with sync on green. It prob goes to a switching
IC just before a D-A converter.

IIRC Sams covered this. Try to find a used ORIGINAL copy. sams
is too much $$ & often a poor quality. Originals are the highest Q.
OEM Zenith manuals suck at this time but they may have info on
the RGB input. They come on fiche that is a PIA to work with or
paper that came loose. Finding a truly complete paper one is HARD.
Training manuals are nice but I dont remember training on them.
May have just missed it. Watch e-bay for OEM. You will probably
need to find the manual number 1st. format is CM###

73 Zeno:smoke:
LFOD !

...

I've been using this set on component with my ps2 and it has worked great. Am I pushing my luck of somthing frying if I don't do or check anything right away? Set has a great picture and overall seems to just "work" which is what I like.

And thank you everyone for the responses

As a teletext junkie, I want to correct some misconceptions. WTBS did carry the Chicago-based service, Keyfax, for a time from 1982 to 84. I'm not sure on who inserted it, but thanks to an ex-Turner employee, I can confirm they had nothing to do with the next teletext service they had in their VBI, Electra. Electra originated in 1983 as a local service in Cincinatti OH, created by Taft Broadcasting and carried over their then-flagship, WKRC-12. It began to be carried over WTBS' national satellite signal in 1985, and was put in the signal by Satellite Syndicated Systems/TEMPO Enterprises, the people in charge of uplinking WTBS to cable companies. They also added their own service, Tempo Text, which carried stock quotes (or sports, depending on the source). Ultimately, both services were discontinued by 1993 thanks to a lack of interest, Zenith not making TVs with teletext decoders anymore, and Taft-- by this point renamed to Great American Broadcasting, and soon afterwards renamed again to Citicasters-- undergoing lots of corporate shakeups meaning no funding (ironically, during said reorganizations, they sold their Hanna-Barbera animation firm to.... Turner).

There were also two different services carried via the Discovery Channel, Infotext (which revolved around agricultural news and such, as well as AP news and sports), and Datavizion, a family-oriented service which carried quizzes, games, etc. as well as a satellite TV guide.

Now, apparently it is possible to extract teletext from S-VHS, so hopefully there are some S-VHS tapes of WTBS from before 1993 that could have pages extracted from them.

Thanks for the info. Business relations for Teletext were really a bowl of spaghetti, from what you have posted.

Regular VHS (as well as S-VHS) would record/playback closed caption data, so I wonder if it would also record/playback Teletext? There might be a lot more around on old tapes than anyone realizes.

Just checked with a colleague of mine who worked on the captioning capability of VHS, who says:

"...normal VHS machines will not record teletext. The data rate is too high. Captioning is a lower rate and gets through.
On S-VHS machines the recording has a wider bandwidth and can record the teletext signal. However there is a comb filter that separates the color from lumance. This destroys the data and needs to be turned off during the teletext interval."