Croma Dots, And how to remove them?

[Coshi]

Hi, I was wondering how to feed a old black and white TV with a B/W signal.
I was thinking I would use the s video cable from the VCR/DVD player and run it to a RF converter.

With this work or am I crazy?

(BTW I'm going to cut the chroma or y Pin on the s-video cable.)

[lnx64]

Yes, killing chroma will result in no chroma dots since there's no chroma to produce the dots.

[wa2ise]

I modified a Channel Master CM7000 CECB so it can give a B&W modulated TV channel output (without chroma).

Idea is this box uses a special analog filter/mixer video chip, and here I just turn off the chroma input. This chip also provides group delay predistortion (like real NTSC TV stations did back in the day). The switch I used for this used to select which RF channel to put the output RF on, 3 or 4. Now I use it to enable or disable the chroma subcarrier. I hardwired the channel selection to channel 4.

[bandersen]

You can also feed the green signal of a component output to an RF modulator.

I wonder if there's any way to expand the luminance to use the full 4.5 MHz bandwidth like in the pre-color days. I bet the image clarity on a well designed set with wide IF and DC restoration like an RCA 630TS would be impressive.

[earlyfilm]

Originally Posted by Coshi

I was thinking I would use the s video cable from the VCR/DVD player and run it to a RF converter.

Coshi,

I think you wrote one thing and meant another.

A RF converter was used to convert a radio frequency analog UHF signal to a radio frequency VHF analog signal.

A RF modulator was used to convert a video and sound frequency signal to a radio frequency VHF or UHF signal.

James.

[Kamakiri]

Maybe I'm alone here, but I have yet to see any B&W set display anything relating to chroma on the screen. Maybe it leads to a more accurate gray scale?

[DaveWM]

you will see it when you look at a color cast program with very saturated colors, and also on some colors that have hard edges and are side by side. Not all sets show this up, but its like a bunch of moving dots that your eye can lock on to and follow across the screen.

[Coshi]

1)Yea, Cheap DVD players and what not seem to make then, plus there's that bright white dashes on the top left or the screen that come and go.

2)yes I meant modulator

3) Whats a Channel Master CM7000

[lnx64]

Well the dashes that come and go is either closed caption or macro vision.

[Phil Nelson]

Originally Posted by Coshi

3) Whats a Channel Master CM7000

https://www.google.com/?gws_rd=ssl#q...+master+cm7000

Phil

[bandersen]

You will only see it if your set has sufficient IF bandwidth to pick up the chroma info centered around 3.58MHz. I've seen it on most 40s TVs after an alignment when viewing color content. I believe by the mid 50s B&W bandwidth was limited to filter out the color info. It's not so bad when you're far away, but up close it's definitely noticeable.

[VintagePC]

Originally Posted by bandersen

You will only see it if your set has sufficient IF bandwidth to pick up the chroma info centered around 3.58MHz. I've seen it on most 40s TVs after an alignment when viewing color content. I believe by the mid 50s B&W bandwidth was limited to filter out the color info. It's not so bad when you're far away, but up close it's definitely noticeable.

I have yet to put an exact date to my own set but it is from sometime in the fifties... and I have another thread here where I posted pictures of its chroma dots. Either it is early 50s, or canadian TV was a bit behind our southern neighbours...