02-10-2020, 07:56 PM
(This post was last modified: 02-10-2020, 07:57 PM by Geordie McBoyne.)
The attachment shows the CRT protection circuit employed in the Ferranti 24K5 projection TV receiver. One half of an EB91 and an ECL80 is used. My interpretation of circuit operation is as follows. In that normal use the triode-pentode is non-conducting by the application to the control grid of the triode section the rectified negative going flyback pulse present a the anode of the frame output valve. The flyback pulse from the line output transformer is supplied to the pentode control grid. Failure of either timebase will result in the ECL80 becoming conductive and reducing the brightness control voltage to a low level thus causing the CRT to be cut-off.
Geordie McBoyne.
Geordie McBoyne.
