26-05-2017, 01:45 PM
(This post was last modified: 26-05-2017, 01:46 PM by ppppenguin.)
One of the big problems in designing a TV set is providing video to drive the CRT. You need lots of volts with wide bandwidth. Hence lots of gain * bandwidth product, something in short supply with earlier valves.
Some prewar EMI sets such as the 702 used what is effectively a small RF power amplifier to feed the detector which drove the CRT directly. They also used a high slope CRT to minimise the swing needed. As valves improved we arrived at the conventional low level detector followed by a video amplifier and, occasionally, a cathode follower. Usually driving the cathode as this was slightly more sensitive than the grid.
The problem arose again in the early days of transistor TVs where making fast high voltage transistors was a hard problem.
It's not hard to imagine that the guy who modified David's 1804 was a skilled engineer from Pye who knew exactly what he was doing.
Some prewar EMI sets such as the 702 used what is effectively a small RF power amplifier to feed the detector which drove the CRT directly. They also used a high slope CRT to minimise the swing needed. As valves improved we arrived at the conventional low level detector followed by a video amplifier and, occasionally, a cathode follower. Usually driving the cathode as this was slightly more sensitive than the grid.
The problem arose again in the early days of transistor TVs where making fast high voltage transistors was a hard problem.
It's not hard to imagine that the guy who modified David's 1804 was a skilled engineer from Pye who knew exactly what he was doing.
www.borinsky.co.uk Jeffrey Borinsky www.becg.tv
