bbctxtproj

Introduction

As a side project to all my other ongoing TV, VCR and teletext repairs, I recently purchased something different for a winter project. Although not that different, it further extends the 2024 50th Teletext anniversary theme. A BBC micro & boxed Teletext adapter ‘Cheese Wedge’ complete with manuals and ROM, specifically bought for the Teletext element, but I’m sure I will get side tracked into its other abilities.

Some background to the adapter Teletext adapter; Wiki extract

The teletext-like “Mode 7” display mode inside the 8-bit BBC Micros made a broadcast teletext adapter an obvious expansion, and the BBC would broadcast telesoftware free over Ceefax. The hardware and software design was created by Graham Toal. The initial software to use the adapter was quite basic, but the BBC decided to rewrite it and produced the Advanced Teletext System in conjunction with GIS. The new ROM software added several features including support for the new Fastext system, which introduced the four coloured buttons subsequently found almost ubiquitously on European remote controls, including the “red button” which remains a feature of digital television broadcasting. A software downloader was also provided in ROM, permitting access to software available via the broadcast medium known as telesoftware. The downloader could be accessed by pressing a function key, this initiating a search for a catalogue of available software and opening a menu displaying the catalogue. Various commands were also provided to access teletext and telesoftware features.

The adapter itself was mains powered with its own power switch matching the one on the BBC microcomputer. Connection to the computer was via a ribbon cable and the only other connector on the adapter was a female 75 ohm TV aerial (in) connector. The adapter contained four manual tuning wheels to receive signals from four different broadcast channels. Once tuned, use of the adapter, including switching channels, was controlled via the computer. Teletext pages were displayed on the computer monitor.

My  BBC Micro Model B & TELETEXT Adapter

BBC Microcomputer TELETEXT Project 1

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Recap The PSU

Looks like the PSU is, as it was when released in 1983. All the paint seals are intact on the screws, meaning all the caps are original, so will all need checking. The RIFAs as usual, have all the tiny case fractures, they will be the first to go. Visually, none of the electros appear to be bulging, curiously one (C17) has red felt markings on the top. It was more tricky to get into than I anticipated, but once in it revealed this unit has been untouched since manufacture, evidenced by the nice clean print side. First to go were the two RIFA smoke bombs C1 .1uF/250 and C2 .01uF/250V, these were starting to crack. I’ve only had .1uF/275/ X2-types in stock, so that will have to suffice for both C1 & C2. I’m sure .01uF was only used due to its smaller size, after all, it’s just mains filter. Both C6 & C8 had gone high ESR, C8 was starting to bulge at the top and could not be stood on its end. Both are Nippon Chemi-con, so were replaced. All the other tested OK, but were still replaced, as I was in there it made sense to do it now.

BBC Microcomputer TELETEXT Project 6BBC Microcomputer TELETEXT Project 7

BBC Microcomputer TELETEXT Project 8 BBC Microcomputer TELETEXT Project 9 BBC Microcomputer TELETEXT Project 10 BBC Microcomputer TELETEXT Project 11 BBC Microcomputer TELETEXT Project 12 BBC Microcomputer TELETEXT Project 13 BBC Microcomputer TELETEXT Project 14

Tested

BBC Microcomputer TELETEXT Project 15 BBC Microcomputer TELETEXT Project 16

Acorn TELETEXT Adapter

BBC Microcomputer TELETEXT Project 17

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BBC Microcomputer TELETEXT Project 22 BBC Microcomputer TELETEXT Project 23 BBC Microcomputer TELETEXT Project 24 BBC Microcomputer TELETEXT Project 25 BBC Microcomputer TELETEXT Project 26 BBC Microcomputer TELETEXT Project 27 BBC Microcomputer TELETEXT Project 28

BBC Microcomputer TELETEXT Project 29BBC Microcomputer TELETEXT Project 30

Next…. But another blog; Microvitec Monitor Restore, Watford Electronics Expansion, Pi-Tube etc

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