External Teletext Decoder. Is there such a thing?

[cmjones01]

Originally Posted by TonyDuell

Are you sure about that? The teletext PCB uses an SAA5243 chip which outputs RGB. It's fed to the video switching/matrix IC in the colour decoder which as far as I can determine keeps it as RGB. I can't see any way for the teletext video to be come PAL in this chassis.

I lived in a shared house with some friends and our TV was an ICC5 for a few years. We used teletext quite a lot and it was just as sharp and clear as any other teletext set - definitely RGB-driven, not PAL. I got to know the insides of the set quite well in order to keep it running, but eventually got fed up with fixing E-W modulator burnups and chasing those wretched MELF resistors around, and we gave up on it. I don't think I kept any bits, though I do have the remains of an ICC5 NICAM decoder somewhere. But I digress.

Chris

[Maarten]

Originally Posted by Studio263

Many of B&O's TV sets of the Teletext era made the output of the Teletext decoder available at the SCART socket, the idea being that it was then possible to record TV programmes complete with Teletext subtitles. That's one idea, but the results may well be in monochrome.

More usefully, the Thomson / Ferguson ICC5 chassis encoded the output of its Teletext decoder as PAL, it wasn't presented as RGB to the screen. As well as this making the text display washed out, fuzzy and subject to the whims of the user colour control, it means that the fully decoded teletext page images are present in the receiver as CVBS and in colour. It may even be present at the SCART socket like this, who knows?

Finding an ICC5 that still works, there's the challenge...

I guess that depends on which ICC5. I've never seen a continental ICC5 that did this or that even had a decoder that could do this, so there may have existed some add-on board especially for recording subtitles. Thomson used ICC numbers quite loosely, just as Vestel does with their chassis numbers as well but it seemed Thomson used a bit more of a structure by adding 3 digits to the chassis number (ICC5000 to 5999 could exist in theory) that actually had some meaning (which meaning is as good as anyone's guess).

[Red to black]

The ICC5 was unusual in this (amongst other) department/s, as to enable the text (and OSG) or external RGB inputs via the scart to be brightness and contrast adjusted by the video processor IC, the RGB was first converted to YUV internally (matrix 1), then after internal processing was converted back to RGB in matrix 2 to drive the tube base output stages in the usual way and consequently the cathodes of the crt itself.
this IC could handle only two RGB input channels, ie. a two into one switch, the scart RGB input took priority, there was no capability to output RGB to the scart.

[Maarten]

The infamous HA11498 decoder chip, also made by Telefunken as U4606, U4646 and/or U4647 I seem to remember. It's coming back to memory now.