Teletext Adapter Service Manual

[maniacminer]

Hi guys,

Does anyone by any chance have a copy of the Teletext Adapter Service Manual?

I have found Service Manuals for every other Acorn product except this one and this is the most complicated wedge!

The back story:

I got a 1st generation cheese wedge adapter in the pile of stuff I got.

A quick look through it with the 'scope shows that it does tune, but the auto-tuning is fluttering around, perhaps the IF needs alignment (hidden in the huge metal box) Using the tuning mode of the TFS 1.0 ROM I get a strong signal that comes and goes about every two seconds. If I ignore the tuning meter and just watch the Teletext on the screen, I am able to get a reasonable signal and I get some Teletext pages from good old TEEFAX (I have been using that on my old Sony TV for about a year now with a Pi)

To drive the wedge, I took the UHF modulator from one of the dead Electrons and put that on a piece of Veroboard with some bypass capacitors, I then checked the signal on the TV and the Teletext is perfect - the actual video display from the Pi is horrid, but it always has been on composite

I have attached a screenshot of the BBC Micro with the TFS ROM installed displaying the home page of TEEFAX, that's the best I've managed to get so far.

Any help would be greatly appreciated

[guesser]

I assume you've got the schematic? I would also like a copy of the service manual for future reference if someone has it.

I had a similar issue with my TTX2000S for the Speccy where the tuning wouldn't stay locked on. That turned out to be a bad ceramic cap near the tuner. I only found it by probing around all over the circuit with the scope to find where the tuning voltage was going wrong.

[maniacminer]

I assume you've got the schematic? I would also like a copy of the service manual for future reference if someone has it.

I had a similar issue with my TTX2000S for the Speccy where the tuning wouldn't stay locked on. That turned out to be a bad ceramic cap near the tuner. I only found it by probing around all over the circuit with the scope to find where the tuning voltage was going wrong.

Yes, thanks, I have the schematic and that helps a little bit. I could see the AFC moving the signal around trying to track the input. I am going to look at another modulator, I have a feeling the Astec UHF modulator from one of the dead Electrons is crap anyway, especially as it is drifting around in frequency, something the TV is very forgiving of, but the wedge is very, very slow at adjusting to change. The tuning pots needed cleaning as well, some contact cleaner and then a pin-head sized blob of carbon contact grease and the pots are behaving themselves now

[IanS]

Yes, thanks, I have the schematic and that helps a little bit.

Can you not bypass the tuner and feed the video in directly to LK3?

[guesser]

I bought some New Old Stock modulators from Germany to build my "Teletext Insertomatic 4000". They're ALPS MDLP3W104A which are "modern" electronically tuned units which I hooked up to the Raspberry Pi I²C pins via a mosfet level shifter. They need a 30 volt tuning supply which I generate with a slightly modified biglive.com "joule thief" and a KA33VTA voltage stabilizer. I have a write-up of the whole Insertomatic here: https://zxnet.co.uk/teletext/insertomatic/

Alternatively you could just bypass the tuner as Ian suggests

Edit to add:
More practically, you can buy basically the same thing in a ready made mains powered unit from all the usual places. I just wanted to integrate four instances into one box so it made sense to build it up from scratch. The ability to tune them from the Pi was a bonus but not really necessary

[1024MAK]

The ASTEC UM1233 UHF Modulators are well known to me for their ability to drift as their temperature changes. I have a TV set up so that six channels are all tuned to about channel 36, so when using or testing a computer that uses a ASTEC UM1233 UHF Modulator, I can channel hop as the modulator output frequency drips...

Mark

[maniacminer]

Yes, thanks, I have the schematic and that helps a little bit.

Can you not bypass the tuner and feed the video in directly to LK3?

Thanks for the info, I had a go today, worked my way through the schematic today and put the video out straight into the SAA5030 via a small capacitor, but I still get "Bad data" at the bottom of every page, despite there being no visible error. I tried another modulator from another dead Electron and the signal doesn't wander anywhere near as much, but the signal is still very noisy.

I am now thinking I've been caught out by the crap modulator and the out of date TFS1.0 ROM that doesn't understand modern Teletext, for example, I don't have the Fastext links at the bottom.

Time to dump this ROM and move onto ATS! It is amazing to see my middle-aged Sony TV able to read the entire magazine, so every page is immediately available

[maniacminer]

I bought some New Old Stock modulators from Germany to build my "Teletext Insertomatic 4000". They're ALPS MDLP3W104A which are "modern" electronically tuned units which I hooked up to the Raspberry Pi I²C pins via a mosfet level shifter. They need a 30 volt tuning supply which I generate with a slightly modified biglive.com "joule thief" and a KA33VTA voltage stabilizer. I have a write-up of the whole Insertomatic here: https://zxnet.co.uk/teletext/insertomatic/

Alternatively you could just bypass the tuner as Ian suggests

Edit to add:
More practically, you can buy basically the same thing in a ready made mains powered unit from all the usual places. I just wanted to integrate four instances into one box so it made sense to build it up from scratch. The ability to tune them from the Pi was a bonus but not really necessary

Yup, I did just that The Block Party sounds fun! Interesting build, I'm surprised you didn't need a fan in that box

I've managed to find a couple of mains powered modulators for £5 each, "Mercury ILS102" they use 12V and use a digital tuning control. Hopefully, I'll have more luck! Just for laughs, I'll try one on a Beeb, as the Beeb UHF is horrible, even by 80s computer standards.

[maniacminer]

The ASTEC UM1233 UHF Modulators are well known to me for their ability to drift as their temperature changes. I have a TV set up so that six channels are all tuned to about channel 36, so when using or testing a computer that uses a ASTEC UM1233 UHF Modulator, I can channel hop as the modulator output frequency drips...

Mark

Yikes! I never realised that these Astec modulators were so poor. I guess I've been lucky to never have had to rely on it for using the computer. We either had mono composite video into a green screen or RGB into a monitor. I don't remember the Spectrum, C64, Amiga, Sega etc. being this bad (could be faulty memory though!) I was just looking at those Electrons and wondering what I was going to do with them, then I remembered they had the same UHF modulator as the Beeb and if it was in the Beeb, then it had to be good... (did Acorn have shares in Microvitec?)

[guesser]

I'm surprised you didn't need a fan in that box

I'm surprised it coped at the "Chunky Fringe" in Harrow this July, the room we were in was sweltering. It's running very cool right now as it's downstairs in the workshop with the radiator turned off and the door closed. The Pi 3 reports it's currently running at 51.5°C

I notice you mention you're using the TFS ROM. I'd recommend blowing an ATS ROM if you have the kit to do so, it's far better, and will let you use the "new" telesoftware system which is what Teefax will be supporting if I ever get around to doing anything with it.

[maniacminer]

I'm surprised you didn't need a fan in that box

I'm surprised it coped at the "Chunky Fringe" in Harrow this July, the room we were in was sweltering. It's running very cool right now as it's downstairs in the workshop with the radiator turned off and the door closed. The Pi 3 reports it's currently running at 51.5°C

I notice you mention you're using the TFS ROM. I'd recommend blowing an ATS ROM if you have the kit to do so, it's far better, and will let you use the "new" telesoftware system which is what Teefax will be supporting if I ever get around to doing anything with it.

LOL Telesoftware, that brings back memories (no particularly good ones) but it would be fun to see some bits of demoware for us to download.

Yup, I did exactly that, I burnt an ATS2.5 ROM (I found a pile of old BBC ROMS, Wordwise+ etc. that I sliced the sticker off and cleaned the quartz window and rejuvenated the pins with a PCB pen and leg straightener tool) and it works perfectly!

I had a good read through this https://heyrick.eu/software/ttx/ttxohiw.html and downloaded the SAA5030 datasheet (the Acorn wedge is a carbon copy) then spent some time on the scope replaced a couple of capacitors and got a nicer looking signal. Now the pages come around just as quickly as the old Sony TV and the clock is perfectly synchronised, no missing second and double speed second tick, no corruption of any kind.

There was a rabbit hole in that wedge, Alice

[1024MAK]

Yikes! I never realised that these Astec modulators were so poor. I guess I've been lucky to never have had to rely on it for using the computer. We either had mono composite video into a green screen or RGB into a monitor. I don't remember the Spectrum, C64, Amiga, Sega etc. being this bad (could be faulty memory though!) I was just looking at those Electrons and wondering what I was going to do with them, then I remembered they had the same UHF modulator as the Beeb and if it was in the Beeb, then it had to be good... (did Acorn have shares in Microvitec?)

They were used in a lot of home computers in the 1980s, including (off the top of my head) ZX80, ZX81, ZX Spectrum, Acorn Atom, Acorn Electron, BBC Micro and so on...
Some like the Dragon 32 and Dragon 64, used a different version. For example the Memotech MTX500 and MTX512 used the Astec 1286 modulator.

But you have to remember that they are analogue technology. And the televisions were also analogue technology. Because the demodulator in the TV also drifted, the automatic frequency control in (most) TVs could stay locked on. Also the analogue TVs were more forgiving. Well, unless you were trying to get teletext, in which case not all TVs were as forgiving as others...

Mark

[guesser]

Yup, I did exactly that, I burnt an ATS2.5 ROM (I found a pile of old BBC ROMS, Wordwise+ etc. that I sliced the sticker off and cleaned the quartz window and rejuvenated the pins with a PCB pen and leg straightener tool) and it works perfectly!

There's an ATS 3.0 which the one beebem ships. I don't know what the difference are (though I suspect articles all about it were broadcast on Ceefax telesoftware!)

If you've got a blank disk inserted and Teefax up and running in ATS, hit F5 and you should get treated to an exciting demonstration of your microcomputer's ability

[maniacminer]

Yup, I did exactly that, I burnt an ATS2.5 ROM (I found a pile of old BBC ROMS, Wordwise+ etc. that I sliced the sticker off and cleaned the quartz window and rejuvenated the pins with a PCB pen and leg straightener tool) and it works perfectly!

There's an ATS 3.0 which the one beebem ships. I don't know what the difference are (though I suspect articles all about it were broadcast on Ceefax telesoftware!)

If you've got a blank disk inserted and Teefax up and running in ATS, hit F5 and you should get treated to an exciting demonstration of your microcomputer's ability

Thanks for that, unfortunately the only ATS 3.0 I could find was for the Morley or Acorn Advanced Teletext Adapter and both of those use the User Port. However, I am happy to report, pressing F5 and downloading the Telesoftware from the catalogue worked fine. It'd be fun to put some simple BASIC games like Hangman, Hi-Lo etc. on there. I suspect it'll take quite a while to download anything substantial

The "digital" UHF modulators arrived and I can now view perfect Teletext via the UHF on the Teletext Adapter and the TV. I took a (rather dodgy) photo of the screen of the old Sony TV for a comparison. The Astec modulator is atrocious in comparison. I'll pop the Beeb apart and make S38 and give the Beeb a go on UHF, just for sake of a nostalgia never endured

I should find myself a new keystrip, the TFS1.0 keystrip ain't much use

[guesser]

Thanks for that, unfortunately the only ATS 3.0 I could find was for the Morley or Acorn Advanced Teletext Adapter and both of those use the User Port.

As I say, the one that ships with BeebEm is the correct ROM for the cheese wedge. As far as I'm aware the "Teletext System" and "Advanced Teletext System" are the same thing. It's just an improved ROM for the same ANE01 interface.

However, I am happy to report, pressing F5 and downloading the Telesoftware from the catalogue worked fine. It'd be fun to put some simple BASIC games like Hangman, Hi-Lo etc. on there. I suspect it'll take quite a while to download anything substantial

It depends how fast I set it to transmit the pages. Obviously you have to trade off download speed for not slowing the service down for everyone else, but telesoftware can be spewed at one page per second if desired
I've yet to write any nice scripts to generate the downloads, the example program and telesoftware catalog were hand assembled. Somebody more competent with BBC BASIC than me might like to write one that runs natively on a Beeb. I could well imagine that the BBC prepared the files that way - it would be neat if the disks survived and turned up!

I should find myself a new keystrip, the TFS1.0 keystrip ain't much use

I've recreated the ATS keystrip from a scan somebody kindly provided on here https://zxnet.co.uk/teletext/documents/ ... ystrip.pdf

[maniacminer]

Thanks for that, unfortunately the only ATS 3.0 I could find was for the Morley or Acorn Advanced Teletext Adapter and both of those use the User Port.

As I say, the one that ships with BeebEm is the correct ROM for the cheese wedge. As far as I'm aware the "Teletext System" and "Advanced Teletext System" are the same thing. It's just an improved ROM for the same ANE01 interface.

I've stuck that ROM image "ATS 3.0.1" onto an EPROM and I'll give it a go. Thanks for the tip.

However, I am happy to report, pressing F5 and downloading the Telesoftware from the catalogue worked fine. It'd be fun to put some simple BASIC games like Hangman, Hi-Lo etc. on there. I suspect it'll take quite a while to download anything substantial

It depends how fast I set it to transmit the pages. Obviously you have to trade off download speed for not slowing the service down for everyone else, but telesoftware can be spewed at one page per second if desired
I've yet to write any nice scripts to generate the downloads, the example program and telesoftware catalog were hand assembled. Somebody more competent with BBC BASIC than me might like to write one that runs natively on a Beeb. I could well imagine that the BBC prepared the files that way - it would be neat if the disks survived and turned up!

I have some discs in the huge pile of stuff, maybe the guy managed to download some of the programs? Is there a list of programs out there?

I should find myself a new keystrip, the TFS1.0 keystrip ain't much use

I've recreated the ATS keystrip from a scan somebody kindly provided on here https://zxnet.co.uk/teletext/documents/ ... ystrip.pdf

Cool, thanks for the link to the keystrip, I've just printed it out and put it on the Master.

The ROM works!

[guesser]

I was meaning maybe the software the BBC used to prepare the downloads survived somewhere.

G7JJF has some disk images of telesoftware download archives.

[eXne]

A bit off topic: GoSDC has a new software version: v1.08 19 May 2019

[maniacminer]

A bit off topic: GoSDC has a new software version: v1.08 19 May 2019

Yes, I did update thanks.

[Pernod]

Seems we're still missing this service manual, can anyone help?

[Dave C]

I have a BBC Wedge Teletext Adaptor with the 2 Rom versions. It is packed away in the loft and has not been used for many years. What can I do with it? Teletext is not broadcast anymore. I do have a load of VHS tapes with recording from the TV on them. I could hook it up to my old video recorder and look at some 20 years old news.

Dave C

[guesser]

I have a BBC Wedge Teletext Adaptor with the 2 Rom versions. It is packed away in the loft and has not been used for many years. What can I do with it? Teletext is not broadcast anymore.

Stick this on a pi and hook it up via a VCR or standalone UHF modulator! https://github.com/peterkvt80/vbit2
It gives you the option of not one, not two, but four new teletext services, automatically updated over the internet.

I do have a load of VHS tapes with recording from the TV on them. I could hook it up to my old video recorder and look at some 20 years old news.

The recording bandwidth of VHS was too low to correctly reproduce teletext signals, however there is a way to extract the datastream by capturing the band limited signal into a PC and running a deconvolution process to attempt to recover the original data, which a small army of people are now doing to reconstruct an archive of radiated teletext broadcasts! https://github.com/ali1234/vhs-teletext
It's a bit more involved than just plugging in the VCR and hitting play though. (Unless you have S-VHS recordings, they should reproduce a somewhat reasonable signal)

[Pernod]

Stick this on a pi and hook it up via a VCR or standalone UHF modulator! https://github.com/peterkvt80/vbit2
It gives you the option of not one, not two, but four new teletext services, automatically updated over the internet.

Are any of these services available online, or do I have to run vbit2 locally to serve the pages?

[guesser]

Are any of these services available online, or do I have to run vbit2 locally to serve the pages?

They are, you can view three of them (Teefax, Ceefax, and Chunkytext) using the teletext viewer on my website (it simulates a tv, so power on, select a channel, select text etc. as you would on a real set). My viewer also currently has an off-air recording of channel 4, and a silly tech demo really doing full motion video converted with Dominic Pajak's teletext-express tool, and some quick and dirty python code to multiplex it with a minimalist teletext service.

The fourth is called Spark and can be viewed on tvark.org where it has a couple of things not present on the vbit2 system as it's using some active content generation which isn't currently released/part of a default vbit2 install.

My viewer serves up the Yorks and Lincs region for Ceefax, but there are multiple regional feeds which you can select from within the vbit-config tool. The Ceefax service is run by Nathan Dane who has his own viewer "tuned" to the Northern Ireland region.

[Pernod]

Are any of these services available online, or do I have to run vbit2 locally to serve the pages?

They are, you can view three of them (Teefax, Ceefax, and Chunkytext) using the teletext viewer on my website (it simulates a tv, so power on, select a channel, select text etc. as you would on a real set).

I meant, is the vbit2 stream available online to feed an emulator?

[guesser]

I meant, is the vbit2 stream available online to feed an emulator?

Vbit2 is what generates the teletext packet stream from a service's page files, which are pulled from various svn and git repositories.
I've got some slightly out of date notes about using it with Beebem on Windows which I should maybe re-visit. I was hoping to implement packet serving directly into vbit2 to get rid of my clunky stopgap python server. Part of that is wanting a more suitable stream format for the job, but that turns into trying to please everyone who has different use cases for a packet interface, and I just haven't had enough round tuits yet for the list of projects here on my desk.

Vbit2 is the core component of all these teletext systems in my opinion as it is what turns a bunch of row data from a heap of page files (for example teefax) into a live teletext datastream with all the page cycling, linking, real-time clock data etc. Here's a crude block diagram of the basic architechture.

The original use case, and what the installation script and vbit-config utility currently set up on a raspberry pi, is a system using raspi-teletext as the packet consumer to generate the proper teletext containing video signal for a TV, and manage downloading and updating the teletext service files for the user.
At the moment you're "on your own" a bit setting up other non raspi-teletext systems, partly because no-one outside a couple of teletext scene people that I chat with directly has shown interest in doing so. If that is changing I'll focus more efforts on user friendly installation and documentation. I'd love to see more people emulating teletext adapters, and doing telesoftware and stuff!

Being potentially up around 270 kbps before protocol overheads (megabyte+ per hour), it doesn't make sense for me to serve packet streams directly to multiple users over the internet (though I have done so in the past to test naive implementations of viewer code etc), so the intention is that people run their own vbit2 system locally only downloading the few kilobytes of page updates. I still want to make it more user friendly to install and set up a local vbit2 on any system that emulators etc can connect to on localhost or over the user's lan, but again, round tuits...

[Pernod]

Being potentially up around 270 kbps before protocol overheads (megabyte+ per hour), it doesn't make sense for me to serve packet streams directly to multiple users over the internet (though I have done so in the past to test naive implementations of viewer code etc), so the intention is that people run their own vbit2 system locally only downloading the few kilobytes of page updates. I still want to make it more user friendly to install and set up a local vbit2 on any system that emulators etc can connect to on localhost or over the user's lan, but again, round tuits...

Fair enough. I have the Acorn Teletext Adapter running in MAME, being served by vbit2 locally. It's basically a straight port from BeebEm at the moment so ATS only and not TFS, though I intend to look into this. I also aim to emulate the later Morley and and GIS Advanced Adapters too.

Using vbit2 locally is very easy and works well, but does require the user to do some research to get things setup and find the repositories for the pages. Was hoping I could just point them to a URL for each channel to simplify usage.

[guesser]

I'll be interested to see what you figure out about TFS.
Hopefully sooner rather than later I'll get something that can be packaged up into a simple one click download and install to Just Work for every use case (ambitious I know )
It'll change the stream format slightly but not drastically, and make it futureproof. That's part of why things aren't progressing really. I want to get all ducks in a row and make all the changes related to this stuff in one go so that people don't have to keep working around a bunch of small changes to how stuff works as has happened in the past
Now that I know there's another "stakeholder" being held up, this stuff will bump up my list

[johnha]

I once wrote a CEEFAX-esque program in BASIC IV on my Master - two programs, one to 'write' the content (CEEFAX-like menus & stories as simple text files) and one to display/navigate them by polling the keyboard. I was blessed with a DataCentre so didn't get beyond loading each page fresh from RAMFS each time. It polls TIME$ for the date & time and for switching 'pages' every 30 seconds (a problem if running off floppy disc).

When the original RISC OS Pi achieved MODE 7 support, it ran fine on that (easy to transfer with DataCentre) but didn't get as far as trying it on an Arch. I later wrote a third program to parse RSS news/sport/etc feeds - downloaded by Netsurf on RISC OS Pi into my file format - creating both menu and 'story' pages in the process. My hope was to download them directly through the Pi and parse them on the fly in BASIC, I found some code to allow pinging an NTP clock from BBC BASIC but couldn't get it to work.

[Dave C]

Well would you Adam and Eve it, there is life in the old Teletext yet. Many thanks guys for this info. I will take a look.
Dave C