Adding Composite Input (Capacitor Question)

[Electronic M]

Originally Posted by ARC Tech-109

That's what I had in mind, DPDT relay to feed the 1st video amp while cutting the DC to the IF amp, composite goes in after the 4.5 sound trap so I still maintain the DC integrity of the grid, did some tests just poking a 1V Hi-Z video signal in and got excellent results.

I've found it unnecessary to cut power to the IF, it doesn't really change the opperation of the Deknis circuit on the CT-100 or 21CT55... If you build it with the socket adapter and use a clip lead to harvest the B+ that goes to one side of the rear most contrast pot next to the HV cage you can make the video mod a completely bolt on/plug in mod...
...With audio that becomes more involved. On the customer set I added a stereo headphone jack to a bracket that screws to the tuner... the jack is configured to short the detector output to the audio input (return the circuit to stock) if the plug from my preamp module is pulled out, but pass both lines to that module in isolation if the plug is in.

If life wasn't so busy I'd build a few more and sell them. I think I did a really good job with it.

[ARC Tech-109]

The reason for doing it this way is so I can mechanically isolate the video input line from the grid of the 1st video amp when using the tuner and then cut the IF amp off when using the video input so I don't get swamped with mixer noise. Not cutting the grid out of the existing circuit as I see no need to and this way the modifications are kept to a minimum.

[Electronic M]

Originally Posted by ARC Tech-109

The reason for doing it this way is so I can mechanically isolate the video input line from the grid of the 1st video amp when using the tuner and then cut the IF amp off when using the video input so I don't get swamped with mixer noise. Not cutting the grid out of the existing circuit as I see no need to and this way the modifications are kept to a minimum.

I haven't seen mixer noise doing it the way I have. Neither circuit noticably interferes with the other when the video amp grid is switched.