Philips G9 with teletext

[Studio263]

Looking through some CES Service Link magazines revealed that there was once a Philips G9 with teletext - well I never!

Sadly there was no picture of it, just of the remote control. However, this looked to be fully engineered and pukka, so presumably the set was made in some quantity too. Model G26C597, has anyone ever seen one?

Any teletext set with a delta gun tube has got to be unusual; I've seen a picture of a GEC one based on the C2110 (etc) but that looked more like a prototype to me rather than something that a dealer would actually try to sell. There may have been one from RBM too, but I don't know which chassis that was - possibly the one with the 26" Toshiba RIS tube?

Teletext and the 110 Deg. delta gun tube that the G9 had must be asking for trouble, I wonder if the clock in the corner was ever readable? Also, if they fitted text to the G9 then presumably it could be fitted to the G8 too? There's no evidence that they did, but it would have been amusing all the same.

[FERNSEH]

Studio263 wrote: "There may have been one from RBM too, but I don't know which chassis that was - possibly the one with the 26" Toshiba RIS tube?"

The Bush BC6333? Employed the TiFax board.

DFWB.

[Tazman1966]

I think the GEC one also had a prototype for the Viewdata experiment too.

[jayceebee]

Radio Rentals converted some 3500s for teletext using the Texas TIFAX decoder with a hard wired keypad, I used to have a copy of the circuit and conversion details. You needed a good strong signal for it work without errors.

I'm also led to believe there were some converted G8 chassis sets but who did these I don't know. I would imagine the conversion would be quite similar to the G9.

John.

[Nuvistor]

This may be a false memory but I thought the introduction of the SAW type filter for the IF strip made resolving Teletext much easier. Designing and aligning the LC filters in the IF strip for best group delay was not easy.
Of course there were better chip sets available as well which would have helped.

[Richard_FM]

Originally Posted by jayceebee

Radio Rentals converted some 3500s for teletext using the Texas TIFAX decoder with a hard wired keypad, I used to have a copy of the circuit and conversion details. You needed a good strong signal for it work without errors.

I'm also led to believe there were some converted G8 chassis sets but who did these I don't know. I would imagine the conversion would be quite similar to the G9.

John.

The Philips model list at VRAT gives G26C594, 5 & 7 as having teletext, all using the G9 chassis.

[Richard_FM]

https://www.radios-tv.co.uk/chassis-...ekco-dynatron/

[Studio263]

Originally Posted by Nuvistor

This may be a false memory but I thought the introduction of the SAW type filter for the IF strip made resolving Teletext much easier. Designing and aligning the LC filters in the IF strip for best group delay was not easy.

That may be true, but the G11 didn't have a SWAF and the teletext versions of that seemed to work well enough. Nor did early versions the B&O Beovision 8800, and a lot of those either came with text or had the module added later.

[jayceebee]

The first Thorn set fitted with teletext from the factory used the standard 9600 non SWAF IF/decoder with quite a complex interface board. There were around a dozen adjustments the most difficult was the video slicing level to get good eye height. The Mullard decoder together with the introduction of the SWAF reduced the amount of adjustments to around four, only RGB and mix levels if my memory is correct.

John.

[Philips210]

Hi

I guess the G9's teletext decoder would have been built with TTL ICs rather than LSI. The Mullard VM6101 teletext decoder used four LSI chips.
I once saw a Teletext RBM set when at Rediffusion though I don't know if these were rented out, it belonged to the service manager. I remember the vast amount of TTL ICs making servicing a little more involved.

I read that a SAWF was well suited for teletext but many earlier set's vision IF stages just had LC tuned circuits and seemed to work OK. As mentioned, the G11 was like that and I believe the KT3/K30 as well.

Regards
Symon.

[Nuvistor]

Thanks for that John, at least my memory was correct. We sold/rented very few teletext sets until around 1979/80 and then the customers we had were not that bothered.

I think the few early ones we did supply were ITT and performance was very dependant on the signal, those who wanted one tended to live where the signal was not that great. One I remember was at the side of a main road but in a dip so the aerial was about the same height as the traffic, TV pictures were OK but Teletext was so so.

[Philips210]

I'm sure we all remember the clockcracker page on teletext. Often those division characters were missing or corrupted with spurious characters with a below par signal. The TV picture could be fine but the text unreliable.

Regards
Symon.

[Welsh Anorak]

We ran a relay system in a small village that couldn't receive terrestrial TV. The signals were split into channels, amplified, then down-converted to VHF. They were then amplified, split, anplified again and distributed and up-converted via Labgear Tele-Vertas at every set. So when teletext arrived there was no chance it would work... Except it did! I remember a TX9 about a mile from the receiving mast and telling them that unfortunately teletext wouldn't work - and there it was, perfect.
A customer of mine had a Rank Z718 22" she had bought from a department store at a reasonable price because they'd lost the remote control. On opening it up I was amazed to find a couple of huge boards bristling with TTL - it was a text set! Curiosity got the better of me, of course, but it soon became clear the 5v regulator had shorted, generously giving 12v to all the chips which weren't impressed. So no text for the customer, but all they wanted was a standard TV.

[jayceebee]

Originally Posted by Tazman1966

I think the GEC one also had a prototype for the Viewdata experiment too.

I can remember seeing the GEC Teletext prototype TV at a technology evening in a hotel in Newcastle Upon Tyne together with Philips N1500 VCRs and Shibaden VTRs around 1976.

The decoder we were told was entirely TTL and was built into the sets stand. It was a huge affair using thumbwheel switches for page selection.

John.

[Sideband]

Originally Posted by Studio263

Looking through some CES Service Link magazines revealed that there was once a Philips G9 with teletext - well I never!

Sadly there was no picture of it, just of the remote control. However, this looked to be fully engineered and pukka, so presumably the set was made in some quantity too. Model G26C597, has anyone ever seen one?


Teletext and the 110 Deg. delta gun tube that the G9 had must be asking for trouble, I wonder if the clock in the corner was ever readable? Also, if they fitted text to the G9 then presumably it could be fitted to the G8 too? There's no evidence that they did, but it would have been amusing all the same.

In short....yes...and I worked on a few. When I was at Philips in Croydon it would have been around 1975/6 that I saw the first Teletext set. This was in fact a modified G8. I believe that there was one model of G8 available with Teletext....either that or there was a conversion kit. Remember that the G9 used the same combined chroma/IF as the later G8's so both were capable of teletext.

It was actually a bit of a bodge, using a TIFAX decoder board (manufactured by Texas Instruments, hence the TI part), there was an interface board and a power supply board. I remember seeing a sheet regarding the connections of the TIFAX board to the chroma/IF board involving several dozen connections all done on the print side so you can imagine that it looked a bit of a rats nest. It only had one-page text, non-contiguous graphics (a black line appeared between different colours) and each page number had to be completed by pressing 'enter' on the remote'...1,2,3 (enter), 1,0,1 (enter) etc. Back in 1976 though we thought it was pretty fantastic to be able to call up a map of the weather forecast.

The TIFAX board was not serviceable by us mere mortals. If any went faulty, we had to return them to Texas Instruments for repair. They would then send a replacement.

I wonder if any sets have survived?

There is an ended listing on ebay https://www.ebay.co.uk/itm/Texas-Ins...4AAOSwQEtbKCtk for the TIFAX board. There was an interface board plugged into this and fitted above it.

[Nuvistor]

A couple of links with some Teletext information.
https://www.radios-tv.co.uk/ceefax-teletext/

https://www.radios-tv.co.uk/Pembers/...otographs.html

[volte-face]

Originally Posted by Tazman1966

I think the GEC one also had a prototype for the Viewdata experiment too.

Originally Posted by jayceebee

I can remember seeing the GEC Teletext prototype TV at a technology evening in a hotel in Newcastle Upon Tyne together with Philips N1500 VCRs and Shibaden VTRs around 1976.

The decoder we were told was entirely TTL and was built into the sets stand. It was a huge affair using thumbwheel switches for page selection.

John.

The GEC prototype set can be seen in this short, and somewhat less than fascinating, BBC Archive video about the launch of Viewdata HERE

[Welsh Anorak]

Interesting clip! I note that Ceefax was apparently already around in 1975, or is the date wrong?
I remember going on a course in the early Eighties at Rediffusion in Blackpool where there was a proud demonstration of Prestel. In the break, several engineers decided to dial up the network to see how it worked. The lecturer was annoyed when he came back due to the cost of the connection. When asked who was responsible, all pointed to the youngest, inexperienced and most innocent - me! Got roundly told off....

[volte-face]

Originally Posted by Welsh Anorak

I note that Ceefax was apparently already around in 1975, or is the date wrong?

I think the date is correct. The video shows a very early Post Office Viewdata effort by the look of it. It took them a a few more years to get it together properly and finally name it Prestel.

The BBC also made an explanatory programme about Ceefax, with a transmission date of July 1975, which is much more interesting than the Viewdata clip. It's in two parts, which are available from these links - Part_1 and Part_2

[MALC SCOTT]

I have a 22 inch RBM Z718 badged as Rank Arena teletext set. It is fitted with the Texas pcb. I also attended the Prestel course at the Rediffusion training school at Poulton- Le - Fylde.