nesdev.org

Does an NES ROM exist where you can show a single color of the palette on the whole screen?

Here's one I just made.

Edit: To change the color, change byte 0x56 with a hex editor to the color you want.

Edit 2: Nevermind, gotta fix it apparently. Give me a few minutes.

Edit 3: See here.

Thanks, but actually, I'd need one where you can change the color by pressing a button. Or where you can actually navigate through the palette with the d-pad as if the colors where arranged on a 2D field:

(So I don't have to press the button 63 times to go from the first to the last color.)

The reason why I need this: Inside my appartment, the CRT TV has some color distortion on the sides due to magnetic fields or whatever. So, to correct it, I need to put a magnet there. And I'd like to have a cartridge where I can go through all the colors to check them. That's why I'd need such a ROM. Then, I would get someone to put it on a cartridge for me.

So something more like this? Up and down add/subtract $10 to the current color, left and right add/subtract $01.

Yeah, exactly. Thanks. Can this ROM be put on an actual cartridge?

Almost definitely yes. It works on powerpak, and doesn't do anything I anticipate being a problem without powerpak's menu being run before it.

JimDaBim wrote:So, to correct it, I need to put a magnet use a degaussing coil to fix it once and for all.

Fixed I used to "fix" a CRT I had temporarily by putting a guitar amp next to it at the right angle, but fixing the internal degauss circuit that likely isn't firing, or manually degaussing it, will do a better job in the long run...

You can degauss the discolored TV using another (working) CRT. Face the screens together, line them up so that the centers are about even, and turn on the CRT. The degaussing coil in the working CRT will degauss both screens.

Once may not be enough, so be sure to give the degaussing coil time to cool off between uses.

And of course, you can use Kasumi's color test to see if the discoloration is gone.

Loopy's palette test shows all colors.

mikejmoffitt wrote:

JimDaBim wrote:So, to correct it, I need to put a magnet use a degaussing coil to fix it once and for all.

The TV itself doesn't seem to be the problem. For example, when I move it around, the color distortion changes positions. And when I have it outside my apartment door, there are no problems at all. It seems more like something else is causing the effect.
So, would a degaussing coil used at the TV even work in this case?
My old TV from 10 years ago eventually got a green hue at the left side after being used for some years. This one was definitely the TV having a problem. But the image on the one I'm currently talking about seems to be distracted by something external. The color problems don't come from inside. At least that's what I assume since they're not always at the same spot depending on the TV's location, and can also completely disappear.
What would you say about it?

tepples wrote:Loopy's palette test shows all colors.

Thanks, but Kasumi's version fits my needs better. I need one color at a time filling the whole screen to see if the magnetic distortion can still be seen with any color.

@Kasumi:
Could you please edit the file one more time so that it starts at color 0 (dark gray)? Also, would you mind to send me the source code?

JimDaBim wrote:The TV itself doesn't seem to be the problem. For example, when I move it around, the color distortion changes positions. And when I have it outside my apartment door, there are no problems at all. It seems more like something else is causing the effect.

CRTs are very sensitive to magnetic fields, including the earth's own. Normally the degaussing coil will fix any potential discoloration when the CRT gets turned on, before it warms up. Places where no discoloration is visible probably have magnetic fields similar to the last place the TV was used before the coil broke.

JimDaBim wrote:@Kasumi:
Could you please edit the file one more time so that it starts at color 0 (dark gray)? Also, would you mind to send me the source code?

Sure, whatever.

Edit: I'm not really sure why you want the source, but I wouldn't use it to try to learn any coding. The NMI doesn't save the registers (because it doesn't need to) among other things.

Joe wrote:before the coil broke.

So, you think the TV itself is broken in some way?

@Kasumi:
Thanks a lot for your help.
Well, I just wanted to see how a source code for a simple ROM like this looks like.

JimDaBim wrote:So, you think the TV itself is broken in some way?

Yep. From your description, it sounds like the shadow mask has become magnetized. The degaussing coil is supposed to demagnetize the shadow mask every time the TV turns on. Since the discoloration isn't going away by itself, the degaussing coil is probably not working.

And you're sure that every TV has something like that, even an older model?