Composite imput

[josephdaniel]

Has anyone ever tried to add a composite video input to a b&w tv set? I would think that it might produce a better picture than going through the I.F. section(s)?

Just curious!

[lnx64]

Better yet, S-Video without the chroma line.

(Yes, I know that would be basically Composite without chroma in the signal, but a dedicated S-Video jack would ensure you are getting NO chroma in the signal).

I didn't do a composite mod, but I did do the S-Video trick, and the results were pure awesome on my 70's-80's black and white set.

http://www.youtube.com/watch?v=PY60CpSXlog

[josephdaniel]

That looks really good! What input did you feed the lumance from the n64 into the rf modulatior?

[lnx64]

I grabbed luma from the N64's S-Video output, and stuck it to the RF modulators S-Video input (since this modulator had a S-Video input too), but did not carry luma.

Then fed it directly to the TV.

[jhalphen]

Hi Joseph Daniel, Hi everybody,

The problem when creating a composite input on the grid of the video output tube is that there is insufficient gain to produce a bright & well-constrasted picture.

French TV collector Pierre Genet therefore developed a composite input buffer amp with adjustable gain + black level control for this specific purpose. The device adds a standard 75 Ohm 1V peak-to-peak composite input to any vintage TV. See the circuit on his site:

http://www.cfp-radio.com/ - site Home

then navigate to "Realisations"
Pass the radio stuff (TSF) & scroll down to the TV section. Click on:

"Preamplificateur video pour anciens televiseurs monochromes"

circuit schematic, parts list & PCB layout in pdf files.
No IC's just two standard transistors.

TV screen shots of with/without the preamp to show its effect.

If you use the circuit, please drop a line to thank Pierre.

Merry Christmas to all !

jhalphen
Paris/France

[ctc17]

Have dont it many times for testing. Like said its never strong enough and sometimes you end up with a negative image depending on how the set is designed.
The picture really isnt noticeably better if the front end is working right. Often its better with the IF and tuner because you can run the fine tuning up to crystallization and 'peak' the video sharpening the picture.

The big improvement is the sound. It gets rid of all the buzzing and video noise, you can easily disconnect the tvs audio source and feed it your line level signal.

I would guess you are talking about 40-60s tube sets?