ADJUSTING COLORS

[LNG724]

Can someone tell me the correct way to adjust colors from scratch on Kortex or WG monitors
used in arcade games? Is there a general rule of thumb for making these adjustments?

[MonMotha]

Most game test modes offer a set of "color bar ramps".  These are red, green, blue, and (usually) white bars that ramp from black to full intensity.

If RGB are each close, adjust contrast so that the full intensity end is not blooming and has immediately discernible change as you start to go down the ramp, brightness until the bottom 1/20th or so of the ramp is not visible (fully black), then adjust each color using gain/cutoff (contrast/brightness for each color) until each colored bar looks the same and white is white.

If RGB are way off relative to each other, you may want to coarsely adjust in each color (especially gain) before doing the contrast/brightness adjustments.  They all play around with each other, so it's an iterative process.

Brightness and contrast are usually on a remote board or the main chassis board.  Color cut-off and gain are often up on the neckboard.  Sometimes a contrast knob isn't present, and you have to adjust each color's gain individually.  Sometimes there are only controls for two colors, and you have to use brightness/contrast to adjust the one that doesn't have individual control then adjust the other two to match.  Depends on the monitor.

If you're talking about white lines showing each of the three colors not on top of each other, then that's a different problem (convergence).  If you're talking about screens of fully one primary (RGB) color showing another color, that's also a different problem (purity or gaussing).  If these are your problems, please clarify as the procedure to adjust is very different.

[LNG724]

Thanks for the response but I do not have color bars to see. My monitors are for amusement games. I need instructions to adjust after I turn everything down and that includes the screen adjustment on the flyback.

[MonMotha]

Almost all video amusement devices have a test mode which includes a color bar pattern.  If your game does not have one, hook up another game that does for initial setting.  You can't really set these things properly from "totally messed up" without some sort of test pattern.  Once you get everything close, you can hook the monitor back up to the game without such a test pattern and tweak brightness/contrast based upon normal game graphics.

If the screen control has been bumped, turn brightness and contrast all the way down, then turn up screen until you get a gray background with retrace lines (raster pattern).  Then turn it down until the gray background just turns black.  Turn up contrast a good way (~80%) and brightness slightly (~20%) and then do what I said in the previous post.

All the settings interact.  If you've never done this before, it may take a little playing around to get good at it.  It's not too tough once you get the hang of it.  You're extremely unlikely to damage anything by playing with the controls I've mentioned (other than possibly screen), so don't be afraid to futz with it until you figure things out.

[kardenm]

None of our games will generate color bars (skill Cherry, Queen Bee-Fruit Holder, Rainbow Reels, Super Draw Poker, Fruit Bonus Cherry 96, Magical Odds, Mystery J&B, Triple Jack, Cherry Master). Is there any procedure to adjust color without a test pattern to work from? Thanks. Really appreciate your help so far.
       This is a Kortek KT-2-VO monitor(board) I am working. I replaced the FBT with one from a parts board, all of the caps and an output transistor. Now my screen is predominately green. All color gain, cut offs,brite, contrast, screen, etc. controls have been played with. I need to start from scratch.

[MonMotha]

This can be done without them, but it's kinda a pain in the butt, especially if you've not done it before.  The procedure I posted originally still works, but if you don't have access to color bars, you have to just make do with whatever you can get.  If anything, the procedure becomes much harder to describe without referencing the test pattern.

Without a test pattern, you'll just have to use an image where you know what it's supposed to look like.  Something that has a good mix of the three RGB colors and white in varying intensities.  You can adjust screen as I mentioned before.  Contrast can be adjusted so that white is bright but doesn't bloom.  For brightness, turn it up until black starts to turn gray, then turn it back down so that black is in fact black.  For color gains and cut-offs, you'll just have to futz with it until white looks white.  Note that brightness is basically cut-off that applies to all three colors while contrast is essentially gain applied to all three colors.

Check your board to make sure it does in fact not have a test mode.  Looks like Cherry Master has a test mode on a DIP switch.  There's probably a bunch of test patterns in there.

If things are too green, you'll probably start by turning down green gain or cut-off.  If the highlights are too green, you need less gain.  If black areas are green tinged, you'll need to turn down cut-off.  If you have a reasonable picture at all, the screen control is probably set properly.

[kardenm]

Thank you so much. I'll get to work on your suggestions and let you know how it turns out.
How can I find if board has a DIP switch for test mode? I dont see any mention of it in the literature I have. Would it say something on the board itself? Board is stamped with ET-97-01 RC. Game display says SKILL CHERRY'97 by AMUCHINE.

[Kevin Mullins]

One tip I use for myself is whenever I don't have any color test pattern is to focus on two colors....

Black and White

"When white is WHITE...... then the other colors are right."

Black levels being adjusted by three things in varying degrees, SCREEN voltage on the flyback, brightness and contrast.

Your overall brightness and contrast will also effect the "pop" in the colors.

I'm not good at describing this method as it's just one of them things you personally develope over time depending on how well you notice different shades of colors and such.

EDIT: Just realized MonMontha had mentioned the principal of blacks and whites as well.
 

[kardenm]

Thank you all for the help. Turns out problem was a bad color pot on the neck board. Was not getting any blue. Once fixed i was able to use all the suggestions to get color adjusted very nice. Thanks again!