FAQFAQ   SearchSearch   MemberlistMemberlist   UsergroupsUsergroups 
 ProfileProfile   PreferencesPreferences   Log in to check your private messagesLog in to check your private messages   Log inLog in 
Forum index » Electronix » Misc
Reduce color saturation
Post new topic   Reply to topic Page 1 of 1 [8 Posts] View previous topic :: View next topic
Author Message
TSM
electronics forum beginner


Joined: 16 Jul 2006
Posts: 12

PostPosted: Sun Jul 16, 2006 4:03 pm    Post subject: Reduce color saturation Reply with quote

Hello, I want to build a circuit with trimmers to reduce the color
saturation of a signal going to a monitor. The signal is made up of
these wires: R, G, B, Sync, GND.

Do I need some IC? Are there any schematics to look at?

Thank you

--
TSM
Back to top
Bob Myers
electronics forum Guru Wannabe


Joined: 25 Jun 2005
Posts: 171

PostPosted: Sun Jul 16, 2006 7:23 pm    Post subject: Re: Reduce color saturation Reply with quote

"TSM" <nonsidice@non.sidice> wrote in message
news:44ba6340.3664899@news.tin.it...
Quote:
Hello, I want to build a circuit with trimmers to reduce the color
saturation of a signal going to a monitor. The signal is made up of
these wires: R, G, B, Sync, GND.

Do I need some IC? Are there any schematics to look at?

Yes, you would need an IC (or more correctly,
SOME active circuit) to do this properly. The
relationship between RGB values and color
saturation across the board is not a simple one.
What you'd basically be doing is converting the
RGB levels into a Y/C representation, and then
varying the relative level of the "C" components -
and then going back to RGB again.

Why, by the way, do you want to do this? There
may be a simpler approach.

Bob M.
Back to top
TSM
electronics forum beginner


Joined: 16 Jul 2006
Posts: 12

PostPosted: Sun Jul 16, 2006 7:45 pm    Post subject: Re: Reduce color saturation Reply with quote

"Bob Myers" <nospamplease@address.invalid> wrote:


Quote:
Why, by the way, do you want to do this? There
may be a simpler approach.


I have a couple of arcade boards to mess with and a Commodore monitor.
While one of the board gives a pretty balanced picture, the other one
has a problem. The colors seem too saturated. Some details can only be
seen when the screen is fading to black, so the overall appearance is
flat.

Thanks for your help.

--
TSM
Back to top
Bob Myers
electronics forum Guru Wannabe


Joined: 25 Jun 2005
Posts: 171

PostPosted: Sun Jul 16, 2006 9:24 pm    Post subject: Re: Reduce color saturation Reply with quote

"TSM" <nonsidice@non.sidice> wrote in message
news:44ba9590.16545240@news.tin.it...
Quote:
"Bob Myers" <nospamplease@address.invalid> wrote:


Why, by the way, do you want to do this? There
may be a simpler approach.


I have a couple of arcade boards to mess with and a Commodore monitor.
While one of the board gives a pretty balanced picture, the other one
has a problem. The colors seem too saturated. Some details can only be
seen when the screen is fading to black, so the overall appearance is
flat.

Have you checked the peak levels of the video
signals these boards are producing for the same
image?

Bob M.
Back to top
TSM
electronics forum beginner


Joined: 16 Jul 2006
Posts: 12

PostPosted: Sun Jul 16, 2006 9:44 pm    Post subject: Re: Reduce color saturation Reply with quote

"Bob Myers" <nospamplease@address.invalid> wrote:

Quote:
Have you checked the peak levels of the video
signals these boards are producing for the same
image?

No, because they don't produce the same image. One is a Neo Geo MVS
and the other one is a Sega STV (Titan). So they are different boards.
The owner is supposed to adjust R, G & B with trimmers on the
monitor's board. But I can't open my monitor any time I want to swap
boards. So I wanted to build some circuit to alter color saturation.

--
TSM
Back to top
Bob Myers
electronics forum Guru Wannabe


Joined: 25 Jun 2005
Posts: 171

PostPosted: Mon Jul 17, 2006 4:33 am    Post subject: Re: Reduce color saturation Reply with quote

"TSM" <nonsidice@non.sidice> wrote in message
news:44bab2ad.23997666@news.tin.it...
Quote:
No, because they don't produce the same image. One is a Neo Geo MVS
and the other one is a Sega STV (Titan). So they are different boards.
The owner is supposed to adjust R, G & B with trimmers on the
monitor's board. But I can't open my monitor any time I want to swap
boards. So I wanted to build some circuit to alter color saturation.

OK - I think I see what your problem is now. Apologies, I was
misled by the use of the word "saturation."

What you're trying to do here really ISN'T reducing the
"saturation" in the standard color use of the word; the problem
is that the cards in question don't do a very good job of
keeping their video signals within standard levels, and they
need you to adjust the video amp gains in the monitor as a
result (or else the cards are likely to overdrive the video
amp and produce the problem you're seeing). If the sync
signals are separate, you MIGHT try simply sticking some
series resistance in the video lines to drop the level as seen
by the monitor - this will cause an impedance mismatch, but
if the signal is fairly low-frequency (and most of these old
arcade games are running at TV rates anyway, so it shouldn't
be that bad), it's not going to be that much of a problem.
Sticking a 25 to 50 ohm* variable resistance (a trimpot) in
series with each video signal, ahead of the monitor inputs
(or just before the output connections at the board) could
let you play with this and see if it helps, at least. If that doesn't
do it, you'd have to work out some way to drop the signal
levels while maintaining the right termination impedance -
which likely would require an active buffer. But try the trimpots
first - they're cheap and easy, and stand at least a fair chance
of working.

Bob M.

* - These values assume a standard 75 ohm video system.
Back to top
TSM
electronics forum beginner


Joined: 16 Jul 2006
Posts: 12

PostPosted: Mon Jul 17, 2006 5:24 am    Post subject: Re: Reduce color saturation Reply with quote

"Bob Myers" <nospamplease@address.invalid> wrote:

Quote:
[...] If that doesn't
do it, you'd have to work out some way to drop the signal
levels while maintaining the right termination impedance -
which likely would require an active buffer. But try the trimpots
first - they're cheap and easy, and stand at least a fair chance
of working.

Thank you very much for your advice, I will try the pots.

By the way... If the result should not be acceptable, wich IC would
you use as a buffer? How would you wire it? I'm worthless at
electronics, so if you could point me to some schematics I would
really appreciate it.

--
TSM
Back to top
jasen
electronics forum Guru Wannabe


Joined: 18 Jun 2006
Posts: 204

PostPosted: Mon Jul 17, 2006 10:05 am    Post subject: Re: Reduce color saturation Reply with quote

aOn 2006-07-16, TSM <nonsidice@non.sidice> wrote:
Quote:
"Bob Myers" <nospamplease@address.invalid> wrote:

Have you checked the peak levels of the video
signals these boards are producing for the same
image?

No, because they don't produce the same image. One is a Neo Geo MVS
and the other one is a Sega STV (Titan). So they are different boards.
The owner is supposed to adjust R, G & B with trimmers on the
monitor's board. But I can't open my monitor any time I want to swap
boards. So I wanted to build some circuit to alter color saturation.

is sounds like you'd get what you want by adjusting gain and bias
(contrast and brightness) saturation is what the colour control on
a TV does.

if you're over-driving the inputs you could gea a saturation problem of
another kind - transistor saturation.

sticking some resistors in the R G abd B wires could help that,
or maybe not, it depends how radically different the two boards are.

Bye.
Jasen
Back to top
Google

Back to top
Display posts from previous:   
Post new topic   Reply to topic Page 1 of 1 [8 Posts] View previous topic :: View next topic
The time now is Mon Jun 26, 2017 2:05 pm | All times are GMT
Forum index » Electronix » Misc
Jump to:  

Similar Topics
Topic Author Forum Replies Last Post
No new posts Re: Transistor Saturation Noway2 Basics 0 Thu Aug 03, 2006 2:38 pm
No new posts FA: Sony PVM-1220 Pro Video Color Monitor $1 tw@emailaccount.com Equipment 1 Wed Jul 19, 2006 6:03 pm
No new posts FA: Sony PVM-1220 Pro Video Color Monitor $1 tw@emailaccount.com Basics 1 Wed Jul 19, 2006 6:02 pm
No new posts Which color LED is most brightness? Boki design 10 Wed Jul 19, 2006 7:38 am
No new posts spice mos transistor saturation bill_jetson321@yahoo.com design 3 Tue Jul 18, 2006 9:42 pm

Copyright © 2004-2005 DeniX Solutions SRL
Other DeniX Solutions sites: Unix/Linux blog |  Unix/Linux documentation |  Unix/Linux forums |  Medicine forum |  Science forum  |  Send and track newsletters


Powered by phpBB © 2001, 2005 phpBB Group