The Story Of The Sinclair Mini TV Range 

Hi Martin, thanks for the comment. Perhaps I could interview you for my Polymath Perspective site, which includes interviews with several ex Sinclair employees? I’m in the middle of a large project at the moment by I’ll be doing more interviews in the spring.

Hi Martin - when I joined Sinclair Radionics in March 1971 as a Electronic Design Engineer you were my boss for a year or so and my first job was working on electronic circuitry to be used to test the first prototype TV tubes ' known as the cofin tube due to its shape'.

Oh dear, there are some things you should never admit.

What an honor to 'meet' you! Thanks for all you have done for us.

Around 1976 while working in the design department of Sinclair Radionics , I made a special version or the TV1b. It was able to receive the transmission tv system used in France. This was the Black & White transmission standard - as I remember the sound used AM instead of FM and the vision was positive modulation instead of negative modulation. To do the R&D on this prototype while in England I used the old 405 line transmitted signals ( which was switched off a year or so later ). This 405 line transmission system also had AM for sound and positive modulation for vision. I made a visit to Paris to test this prototype and it worked but there appeared to be some problems with signal reception , so it was never made in production.

@@brianflint133 Oh that's really interesting. Thanks for posting this! Yes they had positive modulation vision and AM sound in France, rather like our old 405 line system. It meant electrical interference produced bright blips and caused nasty audio effects! Did you stick with 625 lines or adapt it for 819 lines too? I remember tuning into the 405 lines signals on VHF bands I and III using the MTV1 and of course nothing was resolvable even in negative form. The 405 line signals were switched off around 1985 as I recall.

@@brianflint133 Something I really liked about those Microvisions was that they produced an acceptable picture from very weak signals. Although I lived in Worcestershire in the 1970s and early 80s I could receive signals from Southern TV's Hannington transmitter with only a low gain loft aerial. This allowed me to watch Thunderbirds on Saturday mornings!

@@LostsTVandRadio Its long time ago, and it is difficult to remember all of the technical details. The 405 line system has a sound to vision carrier spacing of 3.5 MHz so on this prototype I probably left the sound intermediate frequency at 6MHz ( or may be it was made to be 5.5 MHz ) and changed the sound detector to be AM instead of FM. The TV used a switch mode power supply which used a variable mark to space timing for power regulation and the frequency was the same as the 'line frequency' ie horizontal scanning frequency of 15625 Hz. In fact it was phase-locked to the received signal transmission. I don't know if the French TV standard had the same horizontal scanning frequency. It could not have been too far from the 15625 Hz otherwise it would have required a complete re-design of the power supply . I designed the IC which was made by Texas Instruments and was part of the switch mode power supply and also produce the sawtooth scanning waveforms ( about 250Vpp ) for the electrostatic deflection plates ( line and frame ). Some high voltage small transistors with a collector to base breakdown voltage of 300V were use for this.

@@LostsTVandRadio We had a team of 4 electronic engineers ( myself being one of them ) working on the design of the Mini TV ( 1975 ) One of the engineers who worked on the Tuners for UHF and VHF left the company , so I took over his duties . I remember spending hours in a large Faraday cage with a spectrum analyser doing measures to optimise the sensitivity of the RF reception.

Thanks, I’m pleased you enjoyed the video.

Hi Graham, the development from the 1960s prototype to your 1978 model is discussed in the video.

Hi Claudio. I did not have much to do with the various calculators which were produced in the mid 1970s at Sinclair Radionics. I did however help test the very first calculator ' Executive' calculators which were made on a small production line in 1972.

They might be hard to find after all this time. I know a couple of people to ask so I’ll get back to you. Someone somewhere probably has a a bag of them in their attic!

Thank you, will wait to hear from you.@@tomflint8673

Hi Christopher. There are 3 intergrated circuits in this TV which were custom made ( by Texas Instruments ) and will be unavailable as a spare parts. I designed one of them - the one which provides the driving waveforms to produce the high voltage ( EHT of 1.7 KV )and the deflection waveforms for plates on the tube which scanned the electron beam in the tube. You need to know that this TV is designed to receive the old analogue TV transmissions and will not work with the current digital transmissions.

Hi, I think I have found some. Waiting for them to arrive so I can test them.@@brianflint133