25-09-2016, 08:22 PM
Hi Ed,
I've eliminated any problems with U14, the 4066. I can fully understand why the designer chose the chip, the functions of black level clamp, blanking and sync adder all performed by a single IC. Its an unusual choice of component for the task, you normally find transistors employed to perform these functions.
Referencing to the Black book, the design concept has not changed since the thirties. The output from the camera is amplified then DC restored with black level set to the required voltage level. The next stage is the mixed blanking which is adjusted to same voltage as the black level Finally, the mixed syncs insertion, which is essentially a gated level shift arrangement.
Geordie McBoyne.
I've eliminated any problems with U14, the 4066. I can fully understand why the designer chose the chip, the functions of black level clamp, blanking and sync adder all performed by a single IC. Its an unusual choice of component for the task, you normally find transistors employed to perform these functions.
Referencing to the Black book, the design concept has not changed since the thirties. The output from the camera is amplified then DC restored with black level set to the required voltage level. The next stage is the mixed blanking which is adjusted to same voltage as the black level Finally, the mixed syncs insertion, which is essentially a gated level shift arrangement.
Geordie McBoyne.
