Transistors in TV receivers: 1950s and early 1960s.

[Geordie McBoyne]

From Americanradiohistory Practical Televisionmagazine May 1957.   On page 457 there is the circuit of an experimental transistor timebase circuit on display at the Television Society Exhibition by the General Electric Company of England.    The frame TB is fully transistorised but the output from the line blocking oscillator drives a valve output stage. In 1957 Transistors still hadn't developed sufficiently in to be employed in that part of a TV circuit.  


http://www.americanradiohistory.com/Arch...957-05.pdf

Geordie McBoyne.

[ppppenguin]

I've got several publications about early use of transistors in TVs. The video output stage was a hard nut to crack as it needed both high voltage and high frequency capability. Eventually we had the AF118 but before then there were various proposals. These included high slope CRTs, beanstalk amplifiers (a sort of strange cascode to share the voltage between several devices) and power IF stages. Power IF and high slope CRT makes one think of some pre-war EMI TVs (eg 702) where a multistage TRF and detector drove the CRT directly.

While the frame scan wasn't really a problem for transistors (it's a specialised audio amp) the line scan certainly was. One early solution was scan magnification using complex magnetic fields. Then devices such as the AU102 allowed the scanning of small CRTs by conventional means. Finally in 1967 the Thorn 2000 was the world's first all transistor colour chassis. The LOP used transistors specially developed by Texas Instruments.

After that some manufacturers clung on to valves in the high power stages but not for long. The Philips G8 and Thorn 3000 showed that transistors were suitable for the mainstream.

Which was the last model of CTV to use valves?

[Geordie McBoyne]

"Which was the last model of CTV to use valves?
Hi Jeffrey,
I believe that ITT-KB was still offering a hybrid CTV as late as 1977 in the form of the last of the CVC9 series. The same company introduced their first all transistor CTV in 1976. Chassis was designated as CVC20 and the new receiver employed a PIL CRT.
Last Decca hybrid CTV was made in 1976.

Geordie McBoyne.

[ppppenguin]

ITT-KB were perhaps the most reactionary of CTV makers. Their CVC1 was the only hand wired CTV sold in the UK. By 1976 Philips, Thorn and RBM had been solid state for several years.

Did B&O have some late hybrids?

It was a bold move by Thorn to reject the Mullard/Philips hybrid reference CTV design and plough their own path. Probably driven by their massive presence in the rental market which demanded sets that were easy to service in the field. I don't think any other 1st generation CTV had readily swappable modules. They were aligned on jigs at the factory and so needed minimum adjustment after field replacement. By contrast, transistors almost sneaked into monochrome sets in the early 1960s. Portables were an obvious target. Full size monochrome stayed hybrid more or less unitl the end. The fairly rare Thorn 1600 was an exception. Did anyone else make a full size solid state monochrome set?

[Geordie McBoyne]

One all transistor TV set that doesn't seem to arouse any great interest is the Pye TT1 of 1960 and yet we have here a portable TV with a full size 14" CRT. This set has an internal NiCad rechargeable battery pack which will give up to two hours viewing. The line output stage employs a pair of Texas 2G221 transistors in a stacked arrangement similar to what we see in the BRC 2000.
I was always of the opinion that CRT was a special Cathodeon tube having a gun assembly with a high slope characteristic, in fact the C14/3A is an equivalent to the Mullard AW36-20. The video amplifier delivers 30volts P - P of video to the CRT. Just enough picture contrast.

Geordie McBoyne.

[Murphyv310]

B&O certainly had hybrids into the 70's, not sure of the cutoff though, the DC coupled frame stage was a pain though. Valves in the line stages were from memory were the only ones.
What about Korting?

[Craig]

It isn't quite TV, but Tektronix introduced the first use of transistors in the 575 transistor curve tracer in March 1957. There were only two, in the floating power supply - everything else was valves. Yes you read that right - a device for tracing out transistor characteristics that had two transistors (2N2148 and 2N277) and 35 valves.

By 1960 many instruments used transistors - for example the Type N 600MHz sampling unit used 23 transistors and 7 valves, and lots of funky specialised diodes. Valves were only retained when higher voltage operation was needed that transistors of the day could not handle.

[Craig]

Deleted - posted to wrong thread!

Even worse - I'd posted to the wrong forum!! Pass the pills.......