22-09-2017, 01:36 PM
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?
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?
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
